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 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 102012
 

Dry climates limit the number of diseases that are common in vegetable gardens but there are a few serious problems that should be monitored.

Viruses

A number of common virus diseases occur on vegetable crops. These include, but are not limited to, zucchini yellows, cucumber mosaic, potato leafroll virus, tomato spotted wilt, and tomato mosaic. The only solutions to a virus infection is removal of the affected plants and control of the vectors (other organisms, usually insects, that spread the disease). Control of a serious recurring virus problem may require getting help from a Master Gardener, county extension educator, nurseryman, or other qualified person.

Corn SmutBacteria

Many of the fruit rots and some leaf spot diseases are caused by bacteria. There are no chemical controls for bacteria. The best methods for controlling these diseases are cultural. Keep fruit off the ground and make sure irrigation practices allow plant surfaces to dry between watering. Also, from the garden any refuse from diseased plants.

Fungi

The most common diseases of plants involve fungal pathogens. Some fungal diseases live in the soil and attack the plant through the roots; other fungal pathogens directly attack leaves, stems, flowers, and fruits. Soil diseases are usually controlled through crop rotation, meaning moving each vegetable to a different place in the garden each year. Fungal leaf and fruit diseases can be reduced my allowing foliage to dry between irrigations and keeping plant parts off the ground. Occasionally, fungal diseases may require fungicidal applications.

To learn more about controlling diseases in vegetable gardens, use the following resources:

University of Idaho: Management of Vegetable Diseases in Home Gardens
Cornell University: Minimizing Diseases in Vegetable Gardens
University of Illinois: Controlling Diseases in the Home Vegetable Garden

 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