Vegetables can be protected from insect pests using either conventional or organic control techniques.
Vegetable production in Alabama is always at a high risk of insect damage. Insect pests range from caterpillars and true bugs that devastate our summer crop, to the insects of cool-season crops like aphids and yellowmargined leaf beetles. Warm winter temperatures and high humidity are favorable to the year-round pest activity. Conventional vegetable producers in the Deep South must get a copy of the 2014 SE Vegetable Crop Handbook for complete insecticide recommendations or contact their county Extension office. Organic producers and home gardeners should use the new Extension bulletins available at https://store.aces.edu/. Identify insect pests correctly then think about managing them using integrated pest management tactics.
Conventional vegetable insecticides fall in 18 different categories. Caterpillars can devastate plant stands if not controlled (figure 1); there are many effective insecticides for caterpillars with new modes of action. We have evaluated spinetoram (Radiant) and flubendiamide (Belt, figure 2) in our test plots as stand-alone or rotation products. These insecticides are more selective than synthetic pyrethroids and also are softer on beneficial insects. Repeated synthetic pyrethroid treatments (like bifenthrin) can flare up spider mites in hot weather, so reduce your insecticide applications in unfavorable conditions or shift to selective products. Certain insecticides like chlorantraniliprole (Coragen) and imidacloprid (Admire) can be applied through drip irrigation for early season insect control with long residual. Through a series of demonstration plots at research stations and commercial fields, we have shown that a mixed trap cropping system with Peredovik sunflower and NK300 sorghum can deter leaffooted bug feeding during mid to late summers. Two applications of insecticides like zeta-cypermethrin (Mustang Max) and lambda-cyhalothrin (Warrior) on NK-300 sorghum head reduced 70-90 percent leaffooted bugs without the need for treating the main crop against that pest.
Spider mite outbreaks were common across Alabama and mowing grass close to the crop during hot weather results in greater spread of this pest. High tunnel producers may also experience spider mites due to the lack of rainfall inside the structure. Effective miticides include abamectin (Agri-Mek – also kills Colorado potato beetles), bifenazate (Acramite) and fenpyroximate (Portal – a new product). For squash bug control, bifenthin (Brigade) and dinotefuran (Venom) provided consistent results in field tests. Apply insecticides timely when insects are most vulnerable, use a surfactant as recommended, and follow the preharvest interval mentioned on the insecticide labels before using the products. Rotate insecticides and minimize applications to conserve the natural enemies and pollinators.
Organic vegetable insect control is difficult and labor-intensive in high pest pressure conditions – so PREVENTION is the best strategy. There is more research-based information available today that should be helpful to organic producers and gardeners. Alabama Extension Commercial Horticulture Team now provides intensive hands-on training to organic producers through the small farms educational initiative; please consult a regional Extension agent near you for more information. In organic farming systems, pest prevention through cultural and mechanical tactics is a very important aspect producers must understand since organic pesticides are expensive and should be used as a last resort. In the Deep South, organic farming can be pesticide-intensive and farmers must use approved insecticides in a timely manner (keep multiple products handy for use). Some of the fast-acting contact insecticides that are good for caterpillar control include spinosad (Entrust) and pyrethrum (Pyganic). Some slow acting but effective caterpillar control products include Bacillus thuringiensis or Bt (Dipel, Thuricide, Xentari), Beauveria bassiana (BotaniGard) and neem oil (Molt-X). Alabama IPM studies suggest BotaniGard and Molt-X can be tank-mixed and rotated with paraffinic oil (Suffoil-X) for excellent aphid control. Bt formulation "Xentari" is also very effective against mixed populations of caterpillars and provides consistent fruit quality when used prophylactically (figure 2). Always target the small caterpillars with insecticides when they are in low numbers. Target the immature stages of beetles on foliage (e.g., Colorado potato beetle, yellowmargined leaf beetle, Mexican bean beetle) with insecticides, but hand remove the adults or use some kind of a barrier (insect netting). Spinosad is an extremely toxic organic insecticide that is also effective against flea beetles, yellowmargined leaf beetles and other late-season pests.
Remember to identify insects first and then think of an action plan based on economic thresholds. Do not use the wrong insecticide and face the frustration of crop failure. Rotate products to avoid insecticide resistance and stop spraying if the pest population is low or when natural enemies are abundant. For more information, subscribe to the Alabama IPM Communicator Newsletter to stay connected (visit www.aces.edu/go/87) or join the Alabama Vegetable IPM page on Facebook for receiving free pest alerts.
Ayanava Majumdar is an Extension entomologist, and Mike Reeves and James Miles are regional Extension agents with the Alabama Cooperative Extension System at Auburn University.