Extension Report

Baldwin County Extension Office

302A Byrne Street

Bay Minette, AL  36507

Telephone (251) 937-7176 or

928-0860/943-5061 ext. 2222

FAX (251) 937-7285

Dr. Ayanava Majumdar

Extension Entomologist and Sustainable Agriculture Coordinator

April 26, 2011

Pest Management Recommendations for Organic Vegetable Gardening

This article briefly describes some common botanical and living insecticides that can be used for organic backyard vegetable production. If readers are interested in learning more about organic vegetable production practices, insect and disease identification, then participate in the 3rd Annual Fruit and Vegetable Web Conference on May 4th, 2011 (9 to 11:30 am). Since this is a virtual conference you don’t have to travel and you can watch the conference from any computer by clicking http://www.aces.edu/go/150. Save this article and connect to the meeting on May 4th at 9 am. Before I describe insecticides, here are some important reminders that can reduce dependence on insecticides and protect the environment. 

Grow vigorous vegetable varieties! Organic crop production is harder than the conventional system, and one of the best pest management tools for the organic gardeners is choosing the right plant variety for your garden. Choose vigorous crop hybrids with multiple disease and insect resistance, when available. This will reduce dependence on insecticides that are generally quite expensive.

Organic gardeners should use cultural control tactics. Use mechanical and cultural insect control tactics first to reduce or repel insects on crops. For example, use trap cropping and companion planting to confuse insects from finding your crop. You can use pieces of bird nets and row covers to cover fruits and stem portions to reduce squash bug and vine borers. Stem collars and nets may also work well to keep cutworms away. Try these simple (labor intensive) ideas and reduce dependence on insecticides.

Apply living insecticides the right way! Organic insecticides are often slow acting or don’t last very long after application. Gardeners typically apply live insecticides to the top of the leaves and miss out spraying the undersides. Living insecticides, like Dipel or Thuricide containing live bacterial cells, die in few minutes when applied on top leaves of plants due to direct solar radiation and high foliar temperature common in South Alabama. Botanical insecticides, like neem and pyrethrin, are also susceptible to solar radiation and rainfall. Therefore, it is better to apply high concentrations of organic insecticide on the underside of leaves during evening hours in order to extend the life of products (avoid application if temps reach above 85F). It is also a good idea to treat the bottom stems and soil at the plant base with insecticides in order to contaminate insects jumping off the plant as you spray. Many beneficial insects hunt on top of leaves and treating the underside would minimize exposure. Do not forget to fully treat the growing stem terminals and young leaves. Purchase sprayers with an angled nozzle on the plastic boom which allows easy treatment of the underside of leaves.

Rotate, rotate, rotate! Make sure that you rotate (or alternate) different insecticides so that insects do not become resistant to treatments. Insecticide rotation with soft products also protects the beneficial insects. When buying insecticides, purchase two to three different products after careful planning so you can rotate them; store the insecticides in a cool place away from sunlight for long-term use. You can save more money this way than going out to buy expensive insecticides on an impulse (rushed decision can lead to wrong purchases). Don’t forget to identify the target insect before buying insecticides. To choose an insecticide (organic or regular), visit the ACES website and print the 2011 Home Garden Vegetable Insect Control Guide from http://www.aces.edu/pubs/docs/A/ANR-0500-B/VOL2-2011/home_vegetable_insects.pdf . Take this guide to the store with you and then follow the label directions before application.

Some common insecticides for organic gardening:

Bacillus thruringiensis (or Bt). Did you know Bt is the world’s largest selling organic insecticide? Bt is a stomach poison that paralyzes insect midgut and causes infection in the body that kills the host. As mentioned before, spray Bt on lower leaf surfaces and in shady areas to prolong the life of the product. Caterpillars have to eat the leaves and get enough inoculum to get infected causing slow death. Growing cover crop between vegetable rows is one way of reducing heat reflected from soil and Bt applied under cover crops persists longer than open ground.

Beauveria bassiana: This is also a living insecticide and contains spores of a fungus that is specific to some vegetable insects like aphids, thrips, whiteflies, etc. BotaniGard ES is a formulation that has been tested in research plots in Alabama and was found very effective against aphids in cool-season crops. Mycotrol-O is an organic formulation and may be purchased online from various stores. Do not tank mix Beauveria with fungicides because it will kill the living spores. Shake sprayer very well before spraying as the spores may settle out. All living insecticides should be prepared fresh before application.

Neem products: If you find a neem oil-based product with no azadirachtin in it (check the product label), then apply the product as you would other horticultural oils. Neem oil is a physical poison that may be applied against small insects or small caterpillars. Azadirachtin, an insect growth regulator, is the active ingredient in neem formulations such as Molt-X, Neemix and Aza-Direct sold commonly via websites but seen rarely in stores. Research in Alabama suggested Neem and other horticultural oils in vegetables seem to most effective when alternated with Bt or Beauveria formulations. Oils can burn some crops, so try them in a small area before making a big mistake. Read the insecticide label!

Spinosad products: Although a very effective insecticide against caterpillars, flea beetles and thrips, many gardeners may overlook this product in a typical store. Spinosad (sold by Fertilome and Bonide) is actually derived from bacterial fermentation. Spinosad has fast knock-down and is an excellent insecticide for alternating with other softer products like oils and Bt.

Pyrethrum (pyrethrin): This is a popular botanical insecticide and MGK (Minnepolis, MN) is one of the major manufacturer of pyrethrum in the U.S. Pyganic is an organic formulation and offers quick knockdown of a variety of insects. Pyrethrum is a contact poison and needs to be applied several times throughout the season to get full control of insects. Pyrethrin ready-to-use sprays are easy to find in stores but beware of mixtures of pyrethrin with fungicides like sulfur as they may cause plant injury.

Garlic and cinnamon extracts: These are insect repellents and may not necessarily kill bugs. Cinnamite, a cinnamon-based product, was pulled from the market because it burnt certain plants but it could become available again. Garlic Barrier is sold online and may provide short-term relief from insects.

For subscribing to the free electronic pest management newsletter starting in May 2011, please email a request to bugdoctor@auburn.edu. Readers can also subscribe to the Facebook page ‘Alabama Vegetable IPM’ for receiving pest alerts on your smartphones.

Email address: azm0024@auburn.edu

Phone: 937-7176 or 943-5061, ext. 2222

The Alabama Cooperative Extension System (Alabama A&M and Auburn Universities) in cooperation with the U.S. Department of Agriculture is an equal opportunity educator and employer.