UI Extension Master Gardeners UI Extension Events UI Extension Idaho Landscapes and Gardens Seasonal Topics UI Extension Idaho Landscapes and Gardens Get Answers UI Extension Idaho Landscapes and Gardens UI Extension Idaho's Growing Regions University of Idaho Extension UI Extension Idaho Landscapes and Gardens UI Extension Idaho Landscapes and Gardens Image Map
Aug 172012
 

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 142012
 

No single symptom tells you that trees or shrubs need additional fertilization. Some nutrient deficiency symptoms can be similar to symptoms of cultural problems or diseases. Slow growth rate, small leaves, fewer flowers, smaller fruit, and pale green or yellow (chlorotic) foliage with mottling between the leaf veins may all be signs of nutrient deficiency.

Two methods of determining nutrient deficiencies include:

Soil Testing

Advantages – provides soil pH, levels of K, P, organic matter content and minor nutrients such as iron or zinc.
Disadvantage – does not provide reliable information on N because N is rapidly lost through leaching or removed by plants

Plant Analysis

There are two methods of determining nutrient deficiencies through plant analysis:

Visual symptoms – include length of shoot growth, leaf color, leaf size, and color pattern and timing of leaf drop

Advantages – N and Fe are often the easiest visual symptoms to identify
Disadvantage- symptoms can be deceiving and/or nonspecific

Foliar tissue analysis – provides the concentrations of specific elements in plant foliage (usually leaves)

Advantages – when combined with soil tests it can provide a good picture of nutrient problem(s) – deficiency or toxicity
Disadvantage- nutritional needs for many landscape plants is unknown

 August 14, 2012
Aug 132012
 

Chlorosis
Construction Damage
Deer Damage
Desiccating Wind
Drought Damage
Fasciation
Frost Injury
Girdling Roots — A Problem of Shade Trees
Hail Damage
How to Care for Tree Wounds
Marginal Leaf Necrosis
Mosses and Lichens
Needle Loss
Needle Tip Necrosis
Nutrient Deficiency
Oedema
Overwatering or Poor Drainage
Poor Pollination
Root Problems on Plants in the Garden and Landscape
Salt Damage
Sapsucker Damage
Snow, Ice and Voles
Sunscald
Transplant Shock
Winter Desiccation
Winter Injury (Arborvitae)
Winter injury
Yellowing, Dieback and Death of Narrow-Leafed Evergreens

 August 13, 2012
Aug 132012
 

Apple Scab
Anthracnose Leaf Blight of Shade Trees
Azalea Leaf Gall Causes Crusty Leaves on Your Azalea
Bacterial Crown Gall on Ornamentals in the Landscape
Black Knot
Cercospora Blight
Control of Phytophthora and Other Major Diseases of Ericaceous Plants
Cytospora Canker of Spruce
Diseases of Ground Cover Plants
Gray Mold
Leaf Blight of Hawthorn
Leaf Diseases on Ornamental Trees and Shrubs
Life Cycle and Symptoms of Dutch Elm Disease
Oak Wilt
Pestalotiopsis Blight
Phomopsis and Kabatina Tip Blights of Junipers
Pine Cankers and Dieback
Pine Wilt
Pine Diseases Chart
Plant Disease-Resistant Apple Varieties
Plant These Disease-Resistant Roses, Tested in PNW
Powdery Mildews on Ornamental Plants
Rhizosphaera Needlecast on Spruce
Verticillium Wilt

 August 13, 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
 

Plant Problem (Symptoms) Pathogen Insect Physiological Notes
Plant stunted, weak growth, leaves off color or limbs dying Powdery mildew (white powdery fungus on leaves), rusts (red, black or orange spots on leaves), leaf spot (black spots on leaves borer damage to stem or leaves, look for holes in stems or leaves Poor soil drainage, drought damage, excess soil drainage, planting too deeply, improper soil pH, cold damage, lawn mower damage, sunscald, stem breakage, animal damage Consider working organic matter into soil before planting shrubs or trees to help improve soil aeration and water-holding capacity. Lack of water is the primary cause of death to recently transplanted shrubs and trees
Plants dying suddenly Root rots (fungus) Insect larva attacking roots Over fertilizing, severe drought damage, poor soil preparation When root rot damage is moderate, symptoms may be similar to those of drought damage
Yellowing (chlorosis) Viruses may cause a mottled appearance on the leaves Insect damage to stem or stippling of leaves Nutritional deficiency (N, Zn or Fe), poorly drained soil, over fertilization, mechanical damage to stem N deficiencies occur on lower leaves first and move up the plant. Fe deficiencies result in interveinal chlorosis of the upper leaves first.
Browning of margin or edges of leaves Root rot (fungus) Frost or cold damage, drought damage, transplanting shock, poor soil drainage, excessive fertilization, mechanical damage Frost damage usually occurs in early spring as buds leaf out. Damage may not be visible for a month or more.
Plant fails to flower Bud blight and other fungal diseases of the flowers Aphids, thrips, grasshoppers, and other chewing or sucking insects Plant is too young or excessive vegetative growth over shading High N levels in soils and ideal growing conditions may delay flowering of some plants.
Plant fails to produce berries Fungal diseases at flowering Cold or frost during flowering, plant is a male or a male plant is missing with only female plants present, improper pruning Using hedge shears to prune shrubs usually results in the removal of most of the tip growth and future flower buds. Berry-producing plants are best pruned by removal of individual limbs inside the plant.
Loss of berries before maturity Fungus disease on berries insect larva Drought damage In mild to moderate attacks by floral diseases, the berries may be discolored or deformed.

Taken from: Perennial Ornamental Plants. H.S. Fenwick, Extension Plant Pathologist. University of Idaho College of Agriculture. Current information Series 146, 1977.


 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