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Aug 172012
 
raven

© 2003 Joyce Gross

What is it?

West Nile Virus is a potentially serious illness, with approximately 1 in 150 infected individuals developing WNV meningitis or encephalitis. Although the Centers for Disease Control estimates that four in five infected people will show no signs at all, severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. Among milder symptoms are fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach, and back.

How is it spread?

Although humans can feasibly spread the disease among one another through blood transfusions, organ transplants, breastfeeding, and even between mother and fetus, WNV is typically transmitted from infected birds to humans via disease-carrying mosquitoes. Hundreds of species of birds can be infected with WNV.

finch

Dr. Lloyd Glenn Ingles © California Academy of Sciences

What steps can you take in your garden to minimize your risk?

According to the National Audubon Society, the best way to reduce the presence of WNV in your neighborhood is to keep mosquitoes from breeding in your yard:

  • Discard old tires and aluminum cans and drill drainage holes in the bottoms of items in which water collects.
  • Prevent water from accumulating in flowerpots or barrels and on swimming pool and boat covers.
  • Change the water in birdbaths and pet dishes at least every 3-4 days (some experts recommend every 48 hours).
  • Clean roof gutters, clean and chlorinate swimming pools, and turn over wheelbarrows and plastic wading pools when you’re not using them.
  • Aerate ornamental pools or stock them with mosquito-eating fish.
  • Fill water-collecting tree cavities with soil or sand.
  • Alter your landscaping to eliminate standing water.

For more information on WNV, visit:

 August 17, 2012
Aug 172012
 

Experts agree that only a very small percentage of the insects and spiders in our yards and gardens are actually pests, feeding on our desirable vegetation or infecting it with plant diseases. Indeed, many insects are helpful partners in our gardens, devouring aphids and other plant-eating pests. Pollinators like honeybees and butterflies are essential participants in the reproduction of many flowers, fruits, and vegetables. Some small, stingless wasps or flies assist us by laying their parasitizing young on or inside doomed pests. Although beneficial insects won’t keep our yards pest-free, their contributions should not be underestimated.

Helpful links:

Biological Control: A Guide to Natural Enemies in North America, Cornell University

IPM Online, University of California

caterpillarHelping beneficial insects feel at home

As a gardener, there are things you can do to help sustain natural populations of beneficial insects:

Provide their preferred and alternative foods – Scatter a wide assortment of flowering plants throughout your garden and landscape or cluster them in a designated bed or border. Because different beneficial insects use pollen and nectar at different times, choose diverse plants with long, overlapping bloom periods. Pollinators aren’t the only beneficials that rely on flowering plants. Nectar can help parasitoids (insects that develop in or on another insect pest) span periods when hosts are few. Nectar, pollen, and plant juices can also help predators (insects such as ladybird beetle larvae, above,  that consume other harmful insects) survive times when prey numbers are low.

Provide shelter – Beneficial insects need protection from predators and human disturbances. These beneficial insects can find cover in perennial flower beds, hedgerows, cover crops, and mulches.

Provide water - Bird baths, shallow containers, or temporary puddles, with sticks or rocks for perching, can help beneficial insects through dry periods. Change the water every two or three days to discourage mosquito breeding.

Protect them from insecticides - Broad-spectrum insecticides kill beneficial insects right along with pests. To minimize impacts on beneficial insects, choose chemicals that are less toxic and more specific. Consider these environmentally “softer” alternatives: insecticidal soaps, horticultural oils, botanicals, Bacillus thuringiensis (Bt), and insecticidal products that act specifically as stomach poisons to foliage-feeding pests.

 August 17, 2012
Aug 172012
 
lady beetle

photo J.K.Clark

Description

Convergent lady beetles have black, dome-shaped bodies and up to 13 black spots on their orange to red hind wings. Their alligator-like larvae are orange and blue. Other common aphid-feeding lady beetles have different numbers or shapes of markings.

Life cycle

Convergent lady beetles lay their oblong yellow eggs on plant foliage, with the number of eggs laid dependent on the number of prey available. Development from egg to adult takes about three to six weeks. Adults migrate to mountain canyons or foothills to hibernate in late summer, flying back to the valleys in the very early spring.

Key benefits

Convergent lady beetles feed primarily on aphids but will also consume whiteflies, other soft-bodied insects, and insect eggs. Both adults and larvae are aggressive predators; each day, adults can eat up to 50 aphids, and larvae can devour the aphid equivalent of their body weight.

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Aug 172012
 
Damsel bugsDescription

Damsel bugs are slender, grayish, or tan insects that reach about 3/8-inch in length. They have elongated heads, long antennae, and long legs. The first pair of legs is noticeably thicker than the other two pairs.

Life cycle

Damsel bugs overwinter as adults and lay their eggs in plant tissue. Nymphs look much like adults. About three or four generations occur each year.

Key benefits

Damsel bug adults and nymphs suck the body contents from aphids, small caterpillars, leafhoppers, plant bugs, thrips, and mites. They also prey on insect eggs.

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Aug 172012
 
Green LacewingDescription

Adult green lacewings are slender, light green, ½- to ¾-inch long, with two pairs of large, clear, highly veined wings and golden eyes. They often fly in the evening or at night. Larvae, 1/8- to 4/5-inch long, resemble tiny, light-brown alligators.

Life cycle

Green lacewings overwinter as adults, generally in leaf litter. They lay their tiny oblong eggs at the ends of long, silken stalks. Larvae emerge in about 4-10 days and the larval stage lasts two to three weeks.

Key benefits

Adult green lacewings feed on aphid honeydew, nectar, pollen, and plant fluids, although some species consume a few small insects. Their larvae-also called “aphid lions”-feed primarily on aphids, capturing them with their large pincers and sucking out their body fluids. During several stages of larval development, a single lacewing can consume as many as 750 aphids. Larvae also feed on leafhoppers, spider mites, thrips, mealybugs, psyllids, whiteflies, small caterpillars, immature plant bugs, and other small insects.

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Hover flyDescription

Adult hover flies are generally brightly colored-with black-and-yellow abdominal bands-and closely resemble bees or wasps. They’re typically ½- to ¾-inch long and have two wings. Their larvae, which can reach ½-inch in length, are sluglike, tapered toward the head, and generally marked with a yellow longitudinal stripe on the back. Tell-tale black, oily smears of excrement on plant foliage reveal their presence.

Life cycle

Hover flies lay their whitish to gray oblong eggs singly on their sides near or within aphid colonies. They can have many generations per year.

Key benefits

Nonbiting, nonstinging adult hover flies feed on pollen, nectar, and honeydew from aphids and scale insects. Their larvae consume aphids and other small, soft-bodied insects, including thrips and small caterpillars. A single larva can eat hundreds of aphids in a month. Hover fly larvae can detect low numbers of aphids and are particularly useful early in the season.

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Description

Minute pirate bugs are 1/16-inch long, black-and-white insects with triangular heads and oval bodies. Their very active, pear-shaped nymphs are orange to amber and wingless.

Life cycle

Minute pirate bugs overwinter as adults and reproduce faster than any other common predatory insect. They can develop from egg to adult in as few as 15 days, producing several generations each summer.

Key benefits

Both adults and nymphs suck body fluids from spider mites, thrips, small aphids, white flies, caterpillars, and insect eggs. They are often the first beneficial predators to appear in spring and can destroy 30 or more spider mites each day.

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parasitic waspDescription

Most parasitic wasps are tiny and black.

Life cycle

Parasitic wasps insert their eggs inside the bodies of aphids, loopers, and other hosts. Larvae hatch inside their hosts, killing them and then cutting holes in their bodies to escape. Many generations occur each year.

Key benefits

Parasitic wasps attack aphids, scale, whiteflies, ants, leafminers, sawfly larvae, and many types of caterpillars. They also parasitize the eggs of such insects as codling moths, tomato hornworms, cabbage loopers, imported cabbageworms, and European corn borers.

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Ground beetleDescription

Predacious ground beetles, ¼- to 1¼-inch long, are typically black or dark metallic, with long legs and long antennae. Their larvae are slender, wormlike, and fast-moving and use large pincers to capture their prey.

Life cycles

Predacious ground beetles overwinter as adults. Their larvae can take about a year to develop, and some adults can live two to four years.

Key benefits

Both larvae and adults feed at night on a variety of insects, including armyworms, cutworms, grubs, small snails, and slugs.

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Spider Description

Numbering about 3,000 U.S. species, spiders are a diverse group of predators. They’re distinguished from insects by their two main body parts and eight legs.

Key benefits

In the Pacific Northwest, crab spiders are important predators that contribute to the overall natural control of many pest insects. They are general feeders that do not spin webs but instead lie in wait on foliage, grabbing their prey as it moves closer. Wolf spiders use their running speed to capture prey, which include both harmful and beneficial insects.

 August 17, 2012
Aug 172012
 
techinid fly

photo J.K. Clark

Description

Tachinid flies are large, dark, and bristly, resembling bees, wasps, or houseflies.

Life cycle

Some species lay their eggs on foliage, where a nearby host insect will feed on them. Others glue their eggs to the outside-or insert them inside-the host’s body. The emerging larvae parasitize and kill the hosts. Tachinid flies complete one or a few generations each year.

larvae

photo Earl R. Oatman

Key benefits

Tachinid flies attack the larvae of butterflies and moths, beetles, sawflies, and several other insect orders.

 August 17, 2012
Aug 172012
 
water can

Water is key to container plant health

Principles for maintaining healthy plants in containers are no different than for plants in a garden. However, in practice, container plants require greater attention to detail. Limited soil volume and potential stress create requirements for frequent irrigation and fertilizer and constant monitoring for pests.

Irrigation

There is no easy way to schedule watering of container plants. During hot weather, irrigation may be needed every day. However, it should be recognized that overwatering of container plants is a more common cause of death than is underwatering. With that said, a rule of thumb is to let the top 1-2 inches of soil completely dry between irrigations. When applying water, add a sufficient quantity to allow some water to drain out the bottom of the pot.

Fertilization

A high level of fertility must be constantly maintained in containers to keep plants healthy and attractive. The two best methods for applying fertilizer are to 1) mix a slow-release granular fertilizer into the top few inches of soil in the spring and again in mid-summer, or 2) use a solution of a complete fertilizer once a week when irrigating the containers.

Pest Control

Many insect pests infest container plants to a greater degree than garden-grown plants, especially spider mites. Diseases also can become problematic, especially if plants are stressed. Plants should be monitored frequently to identify pest problems before damage becomes severe. Pest control methods for container plants are identical to those described in the other places in this web site (annuals, perennials, bulbs, Insect and Disease Pests).

Excellent information on container gardening is provided Chapter 19 of the Idaho Master Gardener Handbook.

Kansas State University provides detailed container garden instruction.

 August 17, 2012
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Once established, ornamental grasses tend to be relatively carefree. In general, they require little in the way of fertilizer and water inputs. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.

Mulching

If not done before planting, it is beneficial to mulch around ornamental grasses. This will keep the soil cool, retain moisture, and help with weed control.

hose running

Ornamental grasses need minimal water

Irrigation

Ornamental grasses, in general, should be irrigated less often and to a greater depth than other parts of the landscape. Some fescues and other drought tolerant grasses may need much less water overall. During July and August, a weekly irrigation with about 2 in. of water should be adequate in most soils. In sandy soils, less water should be applied on a more frequent basis. The amount of water applied should be cut back during the cooler spring months, the late fall, and during those infrequent periods of rain.

Fertilization

Most ornamental grasses need very little in the way of fertilizer. They may benefit from a spring application of a fertilizer high in nitrogen at the equivalent of 1-3 lbs nitrogen per 1,000 sq. ft. On the other hand, some years, no fertilizer of any kind may be needed. Determination of requirement is based on growth response. If the previous year, plants were slow growing, small, with yellow color, add some fertilizer.

shears

Grasses can be cut back in fall or winter

Manicuring

The only consistent need for ornamental grasses is removal of dead leaves and flower spikes at the end of the season. For many species, those that break, shatter, or fall over in the winter, this should be done in late fall. For grasses that remain attractive through the winter, this can be done in early spring. Cut grasses back to a height of 4-5 inches before new growth appears.

Weed Control

There are no options to completely replace hand weeding in ornamental grasses. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Perennial weeds that creep into beds create the most difficult problems. If hand cultivation provides inadequate control, it may be necessary to hand apply a herbicide, such as a glyphosate product, by hand with a sponge or other wicking material.

Icy grass

Grasses may benefit from winter protection

Winter Protection

Most adapted ornamental grasses can withstand winters without winter protection. However, a layer of mulch over the crown may allow the plants to be more vigorous in the spring. Proper winter mulching consists of application of 3-4 inches of compost, leaves, wood chips, or other organic matter. The mulch should be removed from around the crowns in early spring to help prevent premature growth of shoots that may be damaged by frost.

For more information on the general care of ornamental grasses, see the following two web sites:

Disease and Insect Control

Ornamental grasses have very few consistent pest problems. However, there are a few organisms that can infest grasses and make them less attractive. Some of these are listed below. For detailed information on control of these insects and diseases, as well as information on other pests, see the Insect and Disease Pests section of this site.

Insect Problems

Mealybugs: Are sucking insects, one species of which can become a problem on the Miscanthus grasses. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection. In cases of serious infestation, the plants will be stunted and go dormant earlier than healthy plants.

Control of mealybugs can be had by spraying the plants with a direct stream of water, using and insecticidal soap, or using a registered insecticide.

snail

Snails often live in the crowns of grasses

Slugs and Snails: Prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces. Although slugs and snails will not do significant damage to most ornamental grasses, the thick foliage may provide a haven from which they will emerge and damage surrounding plants.

Control snails and slugs with baits.

Disease Problems

Leaf Rusts: Are caused by several related fungal pathogens that penetrate and kill leaf tissue. Symptoms are usually typified by a yellow, orange, or brownish discoloration of the upper leaf surface on older leaves. The leaves eventually decline and die. These diseases are usually worse following a wet spring.

Removal of all dead plant material at the end of the growing season helps prevent many leaf spot diseases in subsequent years. In-season control usually requires use of a registered fungicide. Maintaining overall plant health is important in controlling fungal leaf diseases. Ensuring proper aeration among plants will reduce humidity and slow the progress of rusts.

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Bulbs do not require and excessive amount of care, but timing and quantity of inputs are unique relative to other perennials. Here is a guide to care for established bulb gardens.

Mulching

If not done before planting, it is beneficial to mulch the bulb flower bed before heat of summer sets in. This will keep the soil cool, retain moisture, and help with weed control.

Hose

Bulbs require deep watering

Irrigation

Bulbs have a range of water needs, depending on species, but most need soil that is consistently moist. For spring bulbs, except in the case of a very dry spring, irrigation is not usually needed until about the time flower buds appear on the plants. Once started, irrigation will likely be needed until the foliage dies and the bulbs go dormant. Because they are planted deep, bulbs should be irrigated less often and to a greater depth than nearby lawn areas. Summer flowering bulbs will likely need water until first frost.

Fertilization

Bulbs are not considered heavy feeders, but do need an annual application of fertilizer to look their best. Use a complete fertilizer that is relatively high in phosphorus. Apply the equivalent of 2-3 lb nitrogen per 1,000 sq.ft. Timing of application is fairly critical. Bulbs begin growing new roots very early in the spring and need fertility available to start this process. So, the best time to apply fertilizer to spring bulbs is in October or early November. A second option is to apply half the fertilizer in the fall and the other half about the time the plants begin to flower. Summer blooming bulbs do best with fertilizer applied about the time the plants emerge or when they are transplanted outside.

Weed Control

There are no options to completely replace hand weeding in bulbs. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Perennial weeds that emerge before the bulbs can be sprayed out with a glyphosate product. Grasses in irises and gladiolas can be controlled with a grass herbicide containing sethoxydim. Grass controlling herbicides cannot be used on other bulbs without risk of serious injury.

Staking

Some bulb plants, especially summer bulbs, have large flowers and somewhat weak stems. They may need to be tied to stakes or allowed to grow inside a support cage to remain upright and attractive.

Pruners

Foliage should die naturally before pruning

Post-bloom Care

Immediately after the bloom period, all seed heads should be removed. This not only improves appearance, but allows the plant to direct its energy to producing new and larger bulbs. The foliage of bulb plants should be allowed to die naturally (or at least be yellow and dying before removal). Healthy leaves are essential to the process of growing new bulbs. Over a period of a few years, removing the leaves too early will cause the bulbs to become smaller and decline in vigor.

Many gardeners do not like the look of post-bloom foliage in the garden. The unattractive leaves can be masked by planting other types of flowers in the bulb garden that will take up the slack in bloom time while the bulbs complete their growth and decline.

Over a period of several years, some bulb plants, such as daffodils, tulips, and crocuses will produce many bulbs and become crowded. When severe, this crowding will reduce bloom potential and make blooms smaller. This can be solved by uncovering the bulbs, dividing them into single units, and replanting the largest and healthiest of the bulbs at a more appropriate spacing. Dividing is best done in the fall, the usual time for planting bulbs. However, by fall all sign of foliage is gone and it is hard to identify the location of the bulbs. This can be solved by using small stakes to mark the plants before they die, or as a second best option, by simply dividing in late spring when the foliage has declined but still marks the presence of plants. Bulbs that are freshly dug and divided should be replanted as quickly as possible to prevent damage from drying conditions. Although not considered an option of choice in Idaho , spring bulbs can be harvested after blooming and stored in the refrigerator until being replanted in the fall.

Tender summer bulbs

Tender summer bulbs must be harvested and stored in the fall

In all regions of Idaho , the tender summer bulbs, such as dahlia, canna, tuberous begonia, and gladiolas must be harvested at the end of the growing season and stored indoors. Otherwise, the bulbs will be damaged or killed by freezing soil conditions. At the first sign of frost injury on the foliage, the bulbs should be harvested, cleaned, cured, and stored. Proper storage conditions vary by species. Complete discussion of the harvesting and storing process, including proper storage conditions for common summer bulb plants, can be found in a University of Minnesota document written by Mary Meyer.

The University of Illinois provides more general information on growing bulbs.

Forcing Bulbs

The term forcing refers to growing practices that bring bulb flowers into bloom during the off-season. Typically, this process is used to produce indoor flowers during the winter months. For each species, certain environmental constraints must be met to overcome bulb dormancy and allow growth and bloom. For spring bulbs, this usually means cold storage before planting in a pot. For summer bulbs, it may mean supplying specific requirements of light duration. It is beyond the scope of this discussion to provide specific requirements of all plants, but understand it can be done and seek procedures elsewhere. Information on forcing spring bulbs can be found on the University of Kentucky site.

Insect and Disease Control

It is beyond the scope of this site to provide specific pest management information for the large number of commercially available bulb species. Each has unique problems that may be more or less serious. However, there are many pests that are common and infest many types of plants. Diagnostic and simple control information will be given below for these common pests. For detailed information on control of insects and diseases, as well as information of other pests, see the Insect and Disease Pests section of this site.

Insect Problems

Aphids: Also known as plant lice. Small, soft-bodied, sucking insects that cluster on the stems or underside of leaves. Aphids are usually wingless and green, brown, or black in color. Symptoms of infested plants include distorted or curled leaves, presence of sticky sap (honeydew) on the infested surfaces, and misshapen new growth.

Aphids can be controlled with the use of insecticidal soap or a registered insecticide. A strong stream of water directed at the infected plants may knock them from the plant. Many beneficial insects feed on aphids and if an infestation is not too severe, it may be appropriate to be patient and let nature take its course.

Spider Mites: Not actually insects, these miniscule pests are actually related to spiders. They spin protective webs on the underside of leaves and feed by sucking juice from the leaves. Symptoms include color mottling that, at a distance, may appear as a general yellowing of older leaves. Webbing will be presence on the underside of infested leaves. The mites, to small to be easily visible, can be detected by shaking a leaf over piece of clean white paper.

Spider mites prefer dry, dusty environments. Sprinkler irrigation or routine washing of leaves with water usually keep them at bay. A severe infestation may require the use of a registered miticide. Most common insecticides are ineffective against spider mites.

slug

Slugs can damage many bulb flowers

Slugs and Snails: Prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces.

Control snails and slugs with baits.

Thrips: Damage is cause by the larva of this small, four-winged insect. Thrips reside on the underside of leaves and use their rasping mouthparts to scrape away the surface of the leaf after which they feed on the sap. Symptoms appear as white streaks and blotches, more prominent on the underside of the leaf.

A light infestation does little permanent damage to the plant and can be ignored. A heavy infestation will likely require the use of a registered insecticide.

Disease Problems

Root and Bulb Rots: Are caused by the penicillium (blue mold) and Fusarium fungi and the soft rot bacteria that live in the soil. These organisms are worse problems on bulbs that are harvested and stored than on those that are left in the soil over winter. Infected bulbs become soft, pink, or mushy and often have an offensive odor.

Control measures include careful harvesting to prevent injury that provides a point of entry for rot organisms. Infected bulbs should immediately be eliminated.

grey mold on peonies

Grey Mold affects many bulb plants, including peony

Grey Mold or Botrytis: Is caused by a fungus that overwinters in the soil. It infects plant stems that touch moist soil surfaces and splashed onto leafs with rain or irrigation water. Symptoms include water-soaked spots on the leaves that become a slimy, grey mold. Infected tissue quickly collapses and dies.

Control includes removal of infected tissue, both live and dead. In severe cases it may be necessary to apply a preventative fungicide.

Daffodils with virus

Bulb can be affected by chronic viruses

Virus: Not technically alive, viruses are small, disruptive pieces of genetic material that disrupt plant function. Symptoms vary widely and usually include some combination of stunting, yellowing, mottling, or leaf and stem distortion. Viruses are a particularly severe problem on bulbs and other perennials because their long life span and lack of seed propagation create many opportunities for chronic infection.

There are no control measures for viruses other than using resistant varieties or controlling the organisms (usually insects) that transfer them from one plant to another. Prevention involves removing and destroying any infected plants.

Information on control of garden insects and diseases common to Idaho can be found in the online Idaho Master Gardener Handbook.

See specific information on controlling bulb diseases and insects at the University of Connecticut web site.

 

Ornamental onions

Ornamental onions are eye-catching summer bulbs

 August 17, 2012
Aug 172012
 

Planting certain perennial flowers can increase visits to the yard by butterflies and hummingbirds. Both flower color and flower shape create the attraction. Here are a few species that are effective at attracting wildlife.

The attraction of Butterfly Weed

The attraction of Butterfly Weed

Butterflies:
Common Name Scientific Name Regional Adaptation
Aster Aster spp. N, SW, SC, SE, HA
Butterfly Weed Asclepias tuberosa N, SW, SC, SE, HA
Goldenrod Solidago spp. N, SW, SC, SE, HA
Obedient Plant Physostegia verginiana N, SW, SC, SE, HA
Purple Coneflower Echinacea purpurea N, SW, SC, SE, HA
Yarrow Achillea millefolium N, SW, SC, SE, HA
 
Hummingbirds:
Common Name Scientific Name Regional Adaptation
Bee Balm Monarda didyma N, SW, SC, SE
Bleeding Heart Dicentra spp. N, SW, SC, SE, HA
Bugleweed Ajuga spp. N, SW, SC, SE, HA
Butterfly Weed Asclepias tuberose N, SW, SC, SE, HA
Bellflower Campanula spp. N, SW, SC, SE, HA
Cardinal Flower Lobelia cardinalis N, SW, SC, SE, HA
Columbine Aquilegia spp. N, SW, SC, SE, HA
Delphinium Delphinium elatum N, SW, SC, SE
Foxglove Digitalis spp. N, SW, SC, SE, HA
Lupine Lupinus spp. N, SW, SC, SE, HA
Red Hot Poker Kniphofia uvaria SW, SC

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello.
SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston). HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

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Once established, most perennial plants are relatively carefree. In general, they require less in the way of fertilizer and water inputs than do annuals. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.

wood chips for mulching

Wood chips as a mulch layer

Mulching

If not done before planting, it is beneficial to mulch the flower bed before heat of summer sets in. This will keep the soil cool, retain moisture, and help with weed control.

Irrigation

Perennial plants should be irrigated less often and to a greater depth than nearby lawn areas. Many perennial plants have effective rooting depths of up to three feet. During July and August, a weekly irrigation with about 2 in. of water should be adequate in most soils. In sandy soils, less water should be applied on a more frequent basis. The amount of water applied should be cut back during the cooler spring months, the late fall, and during those infrequent periods of rain. A few perennials are adapted to very moist or even saturated soil conditions. These must be watered more often.

Fertilization

Most perennial plants need very little in the way of fertilizer. They may benefit from a spring application of a fertilizer high in nitrogen at the equivalent of 1-3 lbs nitrogen per 1,000 sq. ft. On the other hand, some years, no fertilizer of any kind may be needed. Determination of requirement is based on growth response of the plants. If the previous year, plants were slow growing, small, or yellow in color, add fertilizer at the higher end of the recommendation. If they were growing well and looking nice, add at the low end of the recommendation. If they were vigorous, floppy, and too large, do not add any fertilizer.

seed head

Removing old seed heads will aid flowering

Manicuring

Although relatively carefree, some perennials need attention to remain attractive throughout the summer. Plants that look thin and leggy can be forced to produce more lateral growth by shearing or pinching off the growing point of each stem. Plants that have many stems may produce bigger stems and larger flowers if some of the stems are pruned out. Removing lateral flower buds, leaving only the top-most bud, will also make flowers larger. Plants that fall down or become floppy may need to be staked or interplanted with stiffer, more upright types of plants. Deadheading will prolong flowering of many perennials and make the plants more attractive.

Weed Control

There are no options to completely replace hand weeding in annuals. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Perennial weeds that creep into beds create the most difficult problems. If hand cultivation provides inadequate control, it may be necessary to hand apply a herbicide, such as a glyphosate product, by hand with a sponge or other wicking material.

Perennials may require winter protection

Perennials may require winter protection

Winter Protection

In the fall, perennials (except those that provide some winter interest or seedheads for sustaining birds and other wildlife) should be cut back to a height of 3-4 inches. This will create a more attractive winter landscape and allow the crowns to be covered with a layer of mulch. Proper winter mulching consists of application of 3-4 inches of compost, leaves, wood chips, or other organic matter. The mulch should be removed from around the crowns in early spring to help prevent premature growth of shoots that may be damaged by frost and rot in wet spring climates.

Disease and Insect Control

It is beyond the scope of this site to provide specific pest management information for the large number of commercially available perennial species. Each has unique problems that may be more or less serious. However, there are many pests that are common and infest many types of plants. Diagnostic and simple control information will be given for these common pests in our sections on insects and disease problems. For detailed information on control of insects and diseases, as well as information of other pests, see the Insect and Disease Pests section of this site.

Aphids with a predatory lady bug larvae ©2004 Cornell Plant Pathology Herbarium

Aphids with a predatory lady bug larvae ©2004 Cornell Plant Pathology Herbarium

Insect Problems

Aphids: Also known as plant lice. Small, soft-bodied, sucking insects that cluster on the stems or underside of leaves. Aphids are usually wingless and green, brown, or black in color. Symptoms of infested plants include distorted or curled leaves, presence of sticky sap (honeydew) on the infested surfaces, and misshapen new growth.

Aphids can be controlled with the use of insecticidal soap or a registered insecticide. A strong stream of water directed at the infected plants may knock them from the plant. Many beneficial insects feed on aphids and if an infestation is not too severe, it may be appropriate to be patient and let nature take its course.

Caterpillars can be destructive

Caterpillars can be destructive

Caterpillars: Are the larvae of numerous species of moths and butterflies. These voracious legged worms come in many sizes and colors. Plant symptoms include chewed or completely missing leaves. Some types of caterpillars will roll or fold the leaves and hide inside. Often, frass or droppings are present on and around the plants.

A light infestation can be easily controlled by picking them from the plant a crushing them. Common registered insecticides will effectively kill caterpillars.

Leafminers: Are small insect larvae that burrow under the leaf surface while feeding. Symptoms are easily recognized and exhibit themselves as zig-zag or wandering lines on the upper leaf surface that are lighter in color that the rest of the leaf surface. These are tunnels in the leaves caused by leafminer feeding.

A light infestation of leafminers can be controlled by removing and destroying damaged leaves. A heavy infestation will require the use of a registered systemic type insecticide.

Mealybugs: Are sucking insects that infest stems of many plants. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection.

Control of mealybugs can be had by spraying the plants with a direct stream of water, using and insecticidal soap, or using a registered insecticide.

Spider Mites: Not actually insects, these miniscule pests are actually related to spiders. They spin protective webs on the underside of leaves and feed by sucking juice from the leaves. Symptoms include color mottling that, at a distance, may appear as a general yellowing of older leaves. Webbing will be presence on the underside of infested leaves. The mites, to small to be easily visible, can be detected by shaking a leaf over piece of clean white paper.

Spider mites prefer dry, dusty environments. Sprinkler irrigation or routine washing of leaves with water usually keep them at bay. A severe infestation may require the use of a registered miticide. Most common insecticides are ineffective against spider mites.

Slugs and Snails: Prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces.

Control snails and slugs with baits.

Thrips: Damage is cause by the larva of this small, four-winged insect. Thrips reside on the underside of leaves and use their rasping mouthparts to scrape away the surface of the leaf after which they feed on the sap. Symptoms appear as white streaks and blotches, more prominent on the underside of the leaf.

A light infestation does little permanent damage to the plant and can be ignored. A heavy infestation will likely require the use of a registered insecticide.

Whiteflies: In Idaho are more commonly a problem in greenhouses than they are outdoors. They are small insects with distinct bright white wings that reside and feed on the underside of leaves. Symptoms include the presence of honeydew on leaf surfaces, often accompanied by a lack sooty mold. When disturbed, clouds of the white, rapidly flying insects will rise above the foliage, then quickly resettle.

Trap the flies with yellow sticky boards or use a registered insecticide.

Disease Problems

Damping Off: Caused by fungal pathogens that infect seedlings at soil level, girdling the stems and causing death. Infected seedling will develop tan-colored, soft tissue at the base of the stem. The plants fall over and usually die. Once established and actively growing, plants seldom are affected by damping off.

Control measures include maintaining optimum soil moisture and planting into well-drained soils that are not overly wet. In extreme cases, a soil drench of a registered fungicide can be applied to the soil surface. However, by the time damage is observed it may be too late for control using fungicides.

Leaf Spots: Are caused by numerous fungal (occasionally bacterial) pathogens that penetrate and kill leaf tissue. Symptoms usually start and are worse on older leaves. These diseases are usually worse following periods of wet weather and high humidity.

Removal of all dead plant material at the end of the growing season helps prevent many leaf spot diseases the following year. In-season control usually requires use of a registered fungicide.

Powdery mildew on a perennial plant © 2004 Cornell Plant Pathology Herbarium

Powdery mildew on a perennial plant © 2004 Cornell Plant Pathology Herbarium

Powdery Mildew: Is caused by fungal pathogens. The classic symptom is a whitish, powdery growth present on leaf surfaces. Heavy infections cause distortions on new growth. Infections are often worse during summers that follow damp spring weather. Plants grown in shade are more prone to infection with powdery mildew

Prevention involved growing plants in a sunny location and making sure there is plenty of space and air movement around plants. Control usually requires the use of a registered fungicide.

Root and Stem Rots: Are caused by fungi (occasionally bacteria) that live in the soil. Infected plants initially develop mild wilting symptoms that become progressively worse and may eventually cause death.

Soil pathogens are difficult to control. They can best be prevented by planting resistant varieties, avoiding overly wet soil conditions, and destroying infected plants.

White Mold: Is caused by a fungus that overwinters in the soil. It infects plant stems that touch moist soil surfaces. Symptoms include a slimy, white mold that girdles and collapses the infected tissue. Leaves above the girdled stem wilt and die. In advanced stages, small gray structures that look like mouse droppings form inside a hollowed stem.

Prevention is the best strategy and involves staking stems off the ground, spacing plants to allow air movement around foliage, and irrigating infrequently to allow intermittent drying of the soil surface.

Virus: Not technically alive, viruses are small, disruptive pieces of genetic material that disrupt plant function. Symptoms vary widely and usually include some combination of stunting, yellowing, mottling, or leaf and stem distortion. Viruses are a particularly severe problem on perennials because their long life span and lack of seed propagation create many opportunities for chronic infection.

There are not control measures for viruses other than using resistant varieties or controlling the organisms (usually insects) that transfer them from one plant to another. Prevention involves removing and destroying any infected plants.

Information on control of garden insects and diseases common to Idaho can be found in the online Idaho Master Gardener Handbook.

Diagnosis information and specific control measures for diseases in the landscape is available from the University of Kentucky.

The University of Illinois Extension has published a bulletin on control of common insect pests in flower gardens.

 August 17, 2012
Aug 162012
 

Once established, many annual plants are relatively carefree. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.

mulch

Mulch provides many benefits

Mulching

If not done before planting, it is beneficial to mulch the flower bed before heat of summer sets in. This will keep the soil cool, retain moisture, and help with weed control.

Irrigation

Annual flowers use about the same amount of water as does lawn, equal to about ¼ in. per day during July and August. In most Idaho soils, this means approximately 1 in. of water should be applied every 4 to 5 days. In sandy soils, less water should be applied on a more frequent basis. The amount of water applied should be cut back during the cooler spring months, the late fall, and during those infrequent periods of rain. The simplest method of judging water need is to wait between irrigations for the top 1-2 in. of soil to dry.

Fertilization

In most loam soils, preplant fertilization may be adequate to provide basic nutrient needs for annual plants. However, under conditions of sandy soils or long growing season, there may be benefit in adding a small amount (equivalent of 2-3 lb nitrogen per 1000 sq. ft.) of a fertilizer that is high in nitrogen. Sprinkle the fertilizer on the soil surface and water it in. Make the application in late June or about the time the flowers reach peak bloom.

Manicuring

Some annuals need a little attention to appearance to remain attractive. Plants that look thin and leggy can be forced to produce more lateral growth by shearing or pinching off the growing point of each stem. Plants that fall down or become floppy may need to be staked or interplanted with stiffer, more upright types of plants. Many annuals either do not shed dead flowers or produce seed heads, thus reducing production of additional flowers and making the plants less attractive as the summer progresses. This can be solved by occasionally removing the dead flowers, a practice called “deadheading”.

seed head

Removing old seed heads encourages flowering

Weed Control

There are no control options that completely replace hand weeding in annuals. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Some partially effective herbicides are available to help with weed control in annuals. All of these must be applied after the flowers emerge or are transplanted, but before the weeds emerge. See your county agent or local nurseryman for information on products available.

Disease and Insect Control

With over a hundred species of annual flowers commonly available, it is beyond the scope of this site to provide specific pest management information for each one. However, there are many pests that are common and infest many types of plants. We have compiled information on the most common of these in our pages on insect and disease problems.

For more detail on control of insects and diseases, as well as information of other pests not covered in the sections above, see the Insect and Disease Pests section of this site.

 August 16, 2012
Aug 162012
 
Aphids

Also known as plant lice, aphids are small, soft-bodied, sucking insects that cluster on the stems or underside of leaves. Aphids are usually wingless and green, brown, or black in color. Symptoms of infested plants include distorted or curled leaves, presence of sticky sap (honeydew) on the infested surfaces, and misshapen new growth.

Aphids can be controlled with the use of insecticidal soap or a registered insecticide. A strong stream of water directed at the infected plants may knock aphids from the plant. Many beneficial insects such as ladybeetles and lacewings feed on aphids and if an infestation is not too severe, it may be appropriate to be patient and let nature take its course.

Caterpillars

Caterpillars can quickly damage annual plants

Caterpillars

Larvae of numerous species of moths and butterflies. These voracious creatures come in many sizes and colors. Plant symptoms include chewed or completely missing leaves. Some types of caterpillars will roll or fold the leaves and hide inside. Often, frass (droppings) are present on and around the plants.

A light infestation can be easily controlled by picking larvae from the plant and crushing them. Common registered insecticides will effectively kill caterpillars.

Grubs and Cutworms

Grubs and cutworms are the larval stage of many moths and beetles. Most live in the soil and feed on roots or emerge at night to feed on stems and foliage. Severely damaged plants may die from having the stem or roots severed. Other symptoms include chewed lower leaves and/or wilted or stunted plants that result from root feeding.

Grubs and cutworms can be controlled by handpicking, or using a soil drench of an approved insecticide.

Leafminers

Leafminers are small insect larvae that burrow under the leaf surface while feeding. Symptoms are easily recognized and exhibit themselves as zig-zag or wandering lines on the upper leaf surface that are lighter in color that the rest of the leaf surface. These are tunnels in the leaves caused by leafminer feeding.

A light infestation of leafminers can be controlled by removing and destroying damaged leaves. A heavy infestation will require the use of a registered systemic type insecticide.

Sometimes covering a crop with a floating row cover will exclude the insects from entering the plant.

Mealybugs

Mealybugs are sucking insects that infest stems of many plants. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection.

Control of mealybugs can be had by spraying the plants with a direct stream of water, using an insecticidal soap, or applying a registered insecticide.

Spider Mites

Not actually insects, these miniscule pests are related to spiders. They spin protective webs on the underside of leaves and feed by sucking juice from the leaves. Symptoms include color mottling that, at a distance, may appear as a general yellowing of older leaves. Webbing will be present on the underside of infested leaves. The mites, to small to be easily visible, can be detected by shaking a leaf over piece of clean white paper.

Spider mites prefer dry, dusty environments. Sprinkler irrigation or routine washing of leaves with water usually keep them at bay. A severe infestation may require the use of a registered miticide. Most common insecticides are ineffective against spider mites.

slug

Slugs prefer damp places in the garden

Slugs and Snails

Slugs and snails prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces.

Control snails and slugs with baits.

Thrips

Damage is caused by the larva of this small, four-winged insect. Thrips reside on the underside of leaves and use their rasping mouthparts to scrape away the surface of the leaf after which they feed on the sap. Symptoms appear as small white streaks and blotches, more prominent on the underside of the leaf.

A light infestation does little permanent damage to the plant and can be ignored. A heavy infestation will likely require the use of a registered insecticide.

Whiteflies

In Idaho, whiteflies are more commonly a problem in greenhouses than they are outdoors. They are small insects with distinct bright white wings that reside and feed on the underside of leaves. Symptoms include the presence of honeydew on leaf surfaces, often accompanied by a black sooty mold. When disturbed, clouds of the white, rapidly flying insects will rise above the foliage, then quickly resettle.

Trap the flies with yellow sticky boards or use a registered insecticide.

 August 16, 2012
Aug 162012
 

The larval stage of several insects cause damage to home lawns. The larvae feed on roots and underground stems of grass. A thick, healthy lawn may not be resistant to insects, but will be better able to recover from injury and will be able to tolerate some damage without it being noticeable.

If you suspect insect injury, look closely in the thatch layer and top 1-2 inches of soil for larvae. Make sure you have correctly identified the insect and understand its lifecycle to determine the best course of action for control.

 August 16, 2012
Aug 162012
 

Billbugs are perhaps the most common insect affecting home lawns in Idaho. The adults, which are about 1/4 inch long, can be seen in the spring, walking along sidewalks especially on the southern sides of buildings.

Adult bluegrass billbug

Adult bluegrass billbug crawling on a sidewalk. (Photo courtesy: H.D. Niemczyk, Ohio State University)

The adults are a black weevil, have a long snout and will play dead when disturbed. The adults do very little damage, but in the larval stage billbugs eat grass stems and roots. Adults become active when soil temperatures reach 55º F, usually early to mid-May. The larvae are small (1/8 – 1/4 inch long), white, legless grubs with a brown head.

Billbug Larva and adult.

Billbug Larva (right) and adult. (Photo courtesy: H.D. Niemczyk, Ohio State University)

Lawns damaged by billbugs look like they are drought stressed because the grass blades are basically severed from the roots. Grass blades can be easily pulled out by hand with a light tug. A healthy, vigorously growing lawn will recover from moderate billbug damage and symptoms may go unnoticed. However, under-fertilized lawns or lawns that are otherwise stressed will be more susceptible to billbug damage.

Control. If you have areas with known billbug problems, control measures should be targeted against the adults in the spring when they are active and seen crawling along sidewalks or other exposed areas. Waiting until damage is visible may be too late since the damage has already been done. If targeting larvae, good coverage and movement of the insecticide past the thatch layer are very important. Since adults are on the surface of the turf, they are more easily contacted with insecticides.

 August 16, 2012
Aug 162012
 

White grubs are the larval stage of a beetle known as scarab beetles or more commonly as May/June beetles and masked chafers. White grubs have a characteristic “C” shape, are creamy white, with three pairs of legs and grow to a size of up to 1 to 1¼ inches long.

White grubs

White grubs in grass root zone. (Photo courtesy: A.J. Koski, Colorado State University)

White grubs feed on grass roots causing severe wilting and eventually death of affected lawns. The sod will tend to lift away when pulled, but grass blades will generally stay intact since the grubs have mainly eaten roots. Additionally, skunks and raccoons in search of larvae will cause considerable damage as a result of their digging and feeding on grubs.

Grubs are generally found in the top inch or so of the soil and will go much deeper during the winter months. Masked chafer grubs have a one-year life cycle overwintering as larvae with the adults emerging in mid to late June.

The May/June beetles on the other hand have a three-year life cycle with adults emerging in May and June, laying eggs and the larvae feeding during the summer and overwintering. The second year, when most of the damage occurs, the grubs feed throughout the summer. In the third year, the grubs complete their development in the spring and early summer forming pupae and adults the following year to start the cycle again.

Control. Many insecticides are labeled for white grub control, however, it is very difficult to control white grubs because of the difficulty of getting the chemical into the soil where they are active. Excessive thatch can impede the movement of the chemical into the root zone where grubs are feeding. Core aeration can help increase the effectiveness of insecticide applications. Proper watering will also help, but it is important not to ove- water. Over-watering can actually decrease the effectiveness of insecticides.

Find additional information on billbugs and white grubs at Colorado State University.

 August 16, 2012
Aug 132012
 

Bagworm
Bark Beetles
Conifer Aphids
Cottony Maple Scale
Cutworms and Loopers
Eriophyid Mites
European Pine Shoot Moth & Nantucket Pine Tip Moth
Fall Webworm
Juniper Webworm
Gypsy Moth
Leafhoppers
Leafrollers
Lecanium Scale
Leaf Miner
Oystershell Scale
Pales Weevil, Root Collar Weevil, Root Collar Weevil
Pear Slug
Pine Bark Adelgids
Pine Needle Scale
Pitch Mass Borer
Pine Sawfly
Pine Tortoise Scale
Root Weevils
Scale
Shothole Borer
Skeletonizers
Slugs
Spittlebugs
Spruce Bud Scale
Spruce Needle Miners
Spruce Spider Mite
Tent Caterpillars
Yellow Belly Sapsucker
Zimmerman Pine Moth

 August 13, 2012
Aug 132012
 
University of Idaho

Insects

Encouraging Beneficial Insects in Your Garden
2001 PNW 550 Price: $1.00 (available in hardcopy only)

Honeysuckle Witches’ Broom Aphid
1992 CIS 956 Price: $0.75 (available in hardcopy only)

Locust Borer, The
1988 CIS 829 Price: $0.25 (available in hardcopy only)

Diseases

Bacterial Wetwood and Slime Flux of Trees
1990 CIS 876 Price: $0.25 (available in hardcopy only)

Cytospora Canker Disease in Idaho Orchards
1984 CIS 726 Price: $0.25 (available in hardcopy only)

Diplodia Tip Blight on Ponderosa Pine
1992 CIS 946 Price: $0.50 (available in hardcopy only)

Phytophthora Collar-Rot of Orchard Trees
1985 CIS 752 Price: $0.50 (available in hardcopy only)

Management of White Pine Weevil in Spruce

Physiological

Controlling Iron Deficiency in Plants in Idaho

Controlling Sunscald on Trees and Shrubs
1990 CIS 869 Price: $0.25 (available in hardcopy only)

Nutrient Disorders in Tree Fruits

General

Why Home Fruit Trees Die
1986 CIS 776 Price: $0.25 (available in hardcopy only)

University of Illinois

Cytospora Canker of Spruce
Needle Cast of Spruce
Spruce Spider Mite
Sphaeropsis (Diplodia) Blight

Pine Wilt
Pine Diseases Chart
Phomopsis Blight of Juniper

Cedar Rust Diseases
Phomopsis Tip Blight
Kabatina Tip Blight
Cercospora Blight
Pestalotiopsis Blight
Bagworm
Scale
European Pine Shoot Moth & Nantucket Pine Tip Moth
Zimmerman Pine Moth
Yellow Belly Sapsucker
Pine Bark Adelgids
Pine Needle Scale
Pine Tortoise Scale
Pales Weevil, Root Collar Weevil, Root Collar Weevil
Pitch Mass Borer
Gypsy Moth
Spruce Mite
Spruce Gall Adelgids
Spruce Needle Miners
Spruce Bud Scale
Anthracnose
Apple Scab
Black Knot
Cedar Apple Rust
Cedar Hawthorn Rust
Cedar Quince Rust
Chlorosis
Crown Gall
Gray Mold
Oak Wilt
Powdery Mildew
Verticillium Wilt

Ohio State University

Anthracnose Leaf Blight of Shade Trees
Cedar Rust Diseases of Ornamental Plants
Control of Phytophthora and Other Major Diseases of Ericaceous Plants
Cytospora Canker of Spruce
Diseases of Ground Cover Plants
Disorders of Yew (Taxus) in Ohio
Girdling Roots — A Problem of Shade Trees
Leaf Diseases on Ornamental Trees and Shrubs
Oak Wilt
Powdery Mildews on Ornamental Plants
Rhizosphaera Needlecast on Spruce
Root Problems on Plants in the Garden and Landscape
Sooty Molds on Trees and Shrubs
Verticillium Wilt of Landscape Trees and Shrubs
Yellowing, Dieback and Death of Narrow-Leafed Evergreens

University of Vermont
Pest Management
University of Massachusetts

Helping Trees Recover from Stress

University of Minnesota

Garden: Trees & Shrubs – Insects/Diseases

Ohio State University

plantfacts.osu.edu/faq/
http://ohioline.osu.edu/hyg-fact/3000/3304.html
http://ohioline.osu.edu/b614/index.html

 August 13, 2012
Aug 132012
 
  1. Insects – may include chewing or boring into leaves and stems, or plant parts missing altogether. Leaves may be curled, skeletonized (only the leaf veins remain while the tissue between the veins is missing) or have dead spots from insect feeding. Insects may also spread bacterial, fungal, or viral diseases from plant to plant.
  2. Pathogens (diseases) – includes viruses, bacteria and fungi. Leaves may have circular or irregular patterns of dead or discolored tissue or be completely covered in spores from fungi.
  3. Non-infectious (physiological) – includes nutrient deficiencies and toxicities, environmental stresses, or damage caused by chemicals, animals, weather or equipment
Five Steps to Complete When Diagnosing Plant Problems
  1. Identify the plants species and cultivar if applicable – Determine if growth is normal? Did the plant grow abnormally this year, or did it grow at all? What is the leaf shape and size compared to ideal?
  2. Look for patterns – Are other plants in the area affected too? Are the symptoms uniform or random? Is more than one species affected?
  3. Determine what part(s) of the plant are affected – Are the roots, stem, leaves or branches affected? How has the damage progressed over time?
  4. Look for visible symptoms (abnormal appearances or characteristics of plants) and signs (indirect or direct evidence of a pathogen or insect) – chlorotic (yellowing of plant foliage), necrotic (browning and death of plant foliage), contorted growth, damaged or missing parts. What are the leaf patterns and color? Are any signs of the insect or disease (visible insect body parts or fungus spores) present?
  5. What are the environmental and cultural situations present? Ask questions about management practices (watering and fertilizing), history of the area, weather, soil, and handling of the plant. Find out the current history of the area where the plants are growing. What fertilizers or pesticides have been used? What is the irrigation system and how much/how little water has been applied and when?
 August 13, 2012
Aug 102012
 

Insects should be controlled only when they appear in numbers large enough to be destructive. There are five simple strategies for managing insects in a vegetable garden, effective in either traditional or organic systems.

Clean Up

Be a sanitary gardener. Insects will often overwinter in old garden refuse, so it pays to clean up dead plant material at the end of the year. If you want to keep the organic matter in the soil, till or plow the garden after the last of the crops are harvested.

Plant Care

Maintain good plant health. Healthy plants can often partially defend themselves from pests and will recover from damage quicker.

Physical Control Methods

Use physical barriers and cultural controls. You can keep some types of insects at bay by preventing access to the plants. For example, collars around the lower stems of small plants will foil cutworms.

Biocontrol and IPM

Encourage or release beneficial insects. Encourage the presence of predator insects by allowing the presence of a low level of pest (prey) insects and by avoiding the use of broad-spectrum (kills all insects) insecticides in the garden.

Pesticides Use

Judiciously use pesticides as a last line of defense. For many insects, both organic and synthetic insecticide options are available. If insecticides are used, direct the application to the specific problem rather than broadcast an application across the garden. Also, use products that target the specific insect you are trying to control. Make an effort to identify and use the most ecologically friendly products available. All insecticides are not equal for either efficacy or impact.

Insects that commonly infest Idaho gardens at damaging levels
  • Aphids: These stem and leaf feeders can often be controlled without the use of insecticides. Insecticidal soaps or a hard stream of water that simply knocks them off the plant will usually be sufficient to eliminate damage. Also, aphids will almost always be eliminated by predators if you are patient enough to let them do their work.
  • Grubs and Wireworms: These soil-dwellers are difficult to control and may require the use of a soil-applied insecticide prior to planting. This means knowing the history of the garden plot and realizing the problem exists before you see damage.
  • Cutworms: This pest often kills seedlings and transplants by chewing through the stems at ground level. Cabbage, broccoli, tomatoes and other soft-stemmed transplants are often the victims. Placing cardboard collars around the base of plants is an effective method to prevent damage.
  • Corn Earworm: Control of this pest usually requires the use of an organic or synthetic insecticide product, applied to the green silks once or twice.
  • Slugs: In dry climates, slugs and snails are typically not a problem unless too much water is being applied to the garden. If the problem cannot be solved by reducing irrigation, the use of baits and traps can be partially effective.
  • Cabbage Worms: These slender green caterpillars chew holes and deposit webs on broccoli, cabbage, cauliflower, and kale. When obvious damage is present, they may require control with bacillus (the organic pesticide sold as Bt) or another insecticide.
  • Tomato Hornworms: These large, ferocious-looking caterpillars can defoliate tomato or potato plants within a day or two. Physical control (pick them off the plants and step on them or squeeze them between two rocks) is the best method for eliminating this occasional pest
  • Colorado Potato Beetles: These serious pests of potatoes, when present is small numbers, can be removed from the plants by hand. In large numbers they may require an insecticide.

To learn more about controlling vegetable insects, see the following resources:

From Cornell University: Managing Home Garden Vegetable Pests
From Oklahoma State University (very detailed): Home Vegetable Garden Insect Pest Control
From Organic Garden Pests.com (for tips on organic control of insects): Organic Pest Control

 August 10, 2012
Aug 092012
 

Pesticides are an effective tool for combating numerous problems encountered in the home landscape and garden. When used properly they can save time and labor. Used improperly, however, pesticides can cause damage to plants, people and the environment. It is very important to read and understand the label on any pesticide container. In fact, the label is the law. Keep in mind that all pesticides are potentially poisonous and that improper application or use can be dangerous.

Warning Pesticide Use signThere are several categories of pesticides, and numerous products, available for use in the home garden. Herbicides can be used to control weeds. Some products will kill all vegetation and should be used only where no desirable plants reside. There are a small number of these products that sterilize the soil and prevent growth of any plants for several years. Products that sterilize the soil may also damage nearby trees and shrubs if the roots grow into or are already located in the treated area. Be sure you understand the nature and limitations of any compound applied. Some herbicides can kill seeds as they germinate but do not affect growing plants that are already growing. These can be used to control weeds around shrubs, trees or emerged garden plants. Other herbicides kill only certain types of plants, such as grasses. These can be used to control grass weeds in broadleaf garden plots, or their opposite counterparts can be used to control broadleaf weeds, such as dandelion, in lawns. In a garden, herbicides can make weed management easier, but cannot completely replace hand weeding.

The intended use of insecticides is to kill destructive insects and are often very important for managing garden pests. However, because these compounds are designed to kill animal pests, they are often the most toxic and damaging to the environment of all classes of pesticides. Insecticides can also kill beneficial insects so it is again important to read the label to avoid killing insects that help you out in the war against damaging insects. Insecticides should be used only when needed and then only when using all appropriate precautions.

Fungicides and bactericides are used to control plant diseases and can save your lawn, garden, and landscape plants from disease when applied in a timely manner. For many diseases, fungicides must be applied to the target plants before the disease appears. Consequently, they are often used in a preventative fashion.

For further information on pesticides, please refer to the following links:

For detailed general information on controlling pests in gardens, see chapters 9 – 14 in the Idaho Master Gardener’s Handbook.

For general instruction on reading labels and using pesticides in the home garden, see the following informative University of Idaho publication: Pesticides for the Home Garden and How to Use Them

See the EPA document Citizen’s Guide to Pest Control and Pesticide Safety for a comprehensive treatment of pesticide selection, management, and safety.

View a comprehensive database of pesticide products for home use from the Household Products site.

Purdue University has published A Strategy for Pest Control in Home Gardens outlining non-pesticide strategies for pest control.

For information on storing and disposing of pesticides, follow this link to an informative University of Idaho publication, Idaho Homeowner’s Commonsense Guide to Pesticides.

 August 9, 2012