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 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

The term “organic farming” was first used in England in the early 1940s, emerging from the biodynamic movement in which a farm was perceived spiritually as a dynamic, living “whole organism.” The concept was brought to the United States in the mid 1940s and widely promoted by J.I. Rodale, founder of Organic Farming and Gardening Magazine (now Organic Gardening) and author of Pay Dirt: Farming and Gardening with Composts and How to Grow Fruits and Vegetables by the Organic Method. Rodale strongly believed in the relationship between living soil and healthy food was achieved by returning animal manures and plant debris to the system by way of composts. The United States Department of Agriculture defines organic as as “an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony.

The growing and selling of produce and products labeled “Certified Organic” is strictly monitored by the United States Department of Agriculture involving a rigorous certification process and complicity with federally mandated regulations for exclusion of non-approved crop management materials, such as synthetic pesticides and fertilizers.

Many home gardeners would like to reduce synthetic chemical use around their children, pets and environment. While they won’t need to certify their backyards, home gardeners may adopt some of the recommended practices to grow flowers, vegetables, fruits and even lawns by using biological and cultural controls, composts, and organic fertilizers along with conventional methods. Some gardeners may choose to completely exclude the use of inorganic fertilizers or growth regulators to reduce dependence on non-renewable resources. Whatever the desire and intent, there are some universally applicable concepts that will help the organic gardener succeed.

closeup of row of seedlings in dirtOrganic vegetable gardening promotes and enhances natural diversity and biological cycles. Rather than relying on synthetic fertilizers and pesticides, organic gardening is based on making the garden self-sufficient and sustainable. You can ease your gardening practices into the organic arena by starting with some of the easier aspects of organic gardening, such as mechanical control of weeds and insect pests.

The first step in this transitioning a garden to organic is improving and maintaining soil fertility and quality. Healthy, fertile soils are basic to successful organic vegetable and fruit production. Management and addition of organic matter, in the form of composts, manures, green manures, and plant residues, is the most important principle to understand for maintaining soil productiveness in an organic system. Organic matter in various forms should be added to the soil annually. There are also many organic fertilizers that can be used to supplement plant nutrition, especially to meet the need for nitrogen and phosphorus. Utah State University has published an excellent organic fertilizer guide, Selecting and Using Organic Fertilizers.

Pest management is the most challenging aspect of organic gardening. Weeds can be controlled with cultivation, pulling, or smothering using mulches. Insects must be closely monitored and controlled using various mechanical methods, predator insects, baits and traps, mild soaps or directed water streams. There are several organically certified insecticides that are useful in the control of insect pests, including Bacillus thuringenisis, insecticidal soaps, rotenone, or natural pyrethrins.

Diseases are best managed through the use of resistant varieties. It is also important to purchase and plant disease-free seed to avoid introducing disease pests into the garden as well as remove and discard diseased plants, rotate annual crops to different places in the garden each year, and keep the garden area free of weeds and dead plant material that may harbor disease organisms. Some leaf-infecting fungi can be controlled using organic fungicides.

A comprehensive list of approved organic materials can be found on the Organic Materials Review Institute web site.

Organic gardening can be simple or complex, depending on the desires of the gardener. There is plenty of good information available on the topic from numerous authoritative sources. Here are some of the best:

View a simple introduction to organic gardening concepts from Mississippi State University

For information on a straightforward, but more detailed approach to organic vegetable gardening, visit this list of University of Florida publications.

For an in-depth discussion of organic soil management principles, read Producing Garden Vegetables with Organic Soil Amendments from the University of Florida.

If you wish to move beyond a cursory understanding of organic gardening practices, select from a series of publications from the University of California, Davis describing detailed organic production principles.

 August 9, 2012