Aug 10, 2022Insect Pests Important at Stand Establishment
Fall melon production is underway and transplanting/direct seeding of produce crops is not far behind. So, PCAs will soon be faced with several important insect management decisions. As crops begin to emerge, you can expect to encounter several insect species that can potentially cause serious economic losses to crop stands. These seedling pests include flea beetles, crickets, grasshoppers, darkling beetles, earwigs, and saltmarsh caterpillars (‘woolly worms’). These insects all have chewing mouthparts, and most are capable of consuming large amounts of leaf tissue in a short period of time. Seedling crops at the cotyledon stage are most susceptible; these pests can devour entire cotyledons or outright kill small seedlings. If left unprotected, transplants and larger seedling plants can sustain significant feeding damage on the terminal growing points or newly emerged leaves. Not only can this feeding stunt plant growth but can result in lack of stand uniformity and ultimately, lack of uniform maturity at harvest. Host crop sources for flea beetle, crickets and "woolly worm" infestations include several summer crops (e.g., Sudan grass, cotton, and alfalfa), volunteer melons, and weeds (e.g., purslane, pigweed). I have been seeing a considerable number of pale stripped flea beetles on alfalfa recently. Fortunately, growers have been vigilant about field sanitation, and weeds are few and far between throughout the valleys. Crickets have also been especially abundant this summer, so keep a sharp eye for them, particularly under sprinkler pipe. Salt marsh caterpillars have not been reported to date, but are known to disperse from alfalfa and cotton, particularly Pima cotton (non-Bt). Experience suggests that melon fields planted next to these crops/weedy areas are at a high risk from these seedling pests, particularly flea beetles. As summer crops are harvested or terminated during the next several weeks, these seedling pests typically move to the next available host crop; lettuce, cole crops and melons. Fortunately, there are many registered insecticide alternatives available that can be applied via sprinkler chemigation (i.e., pyrethroids) or foliar sprays (i.e., pyrethroids, methomyl, neonicotinoids) that can cost-effectively minimize their abundance and damage to susceptible produce and melon seedlings. Additionally, insecticide seed treatments are available for lettuce and broccoli that will protect stands from flea beetles and bagrada bug (i.e., NipsIt). For more information on insect pests of leafy vegetables and melons at stand establishment please see Insect Management on Desert Produce and Melons: Pests at Stand Establishment.
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu