We recently compiled the surveys from our annual Lettuce Insect Losses Workshop and results continue to show interesting trends in insecticide usage on desert lettuce. In general, the most used insecticides in fall and spring lettuce correspond directly to the key pests that typically occur during these growing periods. Overall, the pyrethroids applied both as foliar sprays and through chemigation at stand establishment were the most used insecticide class.in conventional lettuce production. No surprise there. Over the past 18 years, pyrethroid usage has remained steady and the reason is quite clear- pyrethroids are the most inexpensive and safe broad-spectrum insecticides available for use in tank-mixtures for effective control of beetles, crickets, and some plant bugs. The overall use of OPs and carbamates increased compared to the last 2 seasons. On spring lettuce, methomyl and acephate usage was higher than the previous 5 years, likely due to the threat of thrips transmitted INSV. In the past few years, OPs/carbamates have been increasingly replaced by several reduced-risk chemistries, of which the spinosyns are the most used class of selective insecticides. Radiant usage against both lepidopterous larvae and thrips has remained steady over the past 18 years, averaging over 2 sprays per treated acre, and remained high in 2021-22. The Diamides (Coragen, Besiege, Minecto Pro, Exirel and Verimark, and Harvanta) were another commonly used selective chemistry in lettuce this season. Since they were first registered in 2008, PCAs have steadily incorporated this new chemical class into their management programs and were used on > 80% of the fall lettuce in 2021. Among the diamides, Harvanta and Besiege were the most used products. Another important class of chemistry used in fall and spring lettuce are the neonicotinoids (the 3rd most used chemistry in lettuce in 2021) driven primarily by soil-applied imidacloprid for whiteflies and aphids. The usage of imidacloprid on both fall and spring lettuce has increased markedly since 2009 but decreased in 2021-22 where it was used on <70% of fall and spring acres. Foliar neonicotinoid usage decreased slightly last season on both fall and spring acres. However, Movento was applied on a greater number of spring acers in 2022 and was the most used product for sucking insect control due to the lettuce aphid outbreaks that occurred. Sequoia, Sivanto, Beleaf, PQZ and Versys were used on more acres last spring, again due to the heavy aphid pressure. Torac usage was up slightly last spring for thrips management but was only used on about 5% of the acreage. In organic lettuce, Entrust was the most commonly applied biopesticide. Like Radiant, it was applied more than two times on 100% of the fall and spring acres. Pyrethrins and azadirachtin/neem oil products were the second most used biopesticides on organic crops. Finally, among all insecticide chemistries, the broad spectrum, consumer–friendly pyrethroids have been the predominant chemistry applied to lettuce. However, for the past 12 seasons PCAs treated a greater percentage of their lettuce acreage with selective, reduced-risk products than with the broad-spectrum chemistries. To view the report of the estimated insecticide usage by chemical class, as well as the most used insecticides on fall and spring lettuce this past growing season, go to this link: Insecticide Usage on Desert Lettuce, 2022-22.
