Results from the recent Lettuce Insect Losses Workshop reveal some interesting trends in insecticide usage on desert head lettuce. Data were summarized from PCA and grower surveys completed over the past 7 years. When compared by class of chemistry using the IRAC mode of action classification system, the pyrethroids, applied both as foliar sprays and chemigations, have consistently been the most commonly used insecticide class by far. Over the past few years their usage has been declining, but only slightly. The spinosyns (Radiant and Success) are the second most commonly used class of insecticides, where their usage increased this season compared. In contrast, estimates of diamide usage (Coragen, Voliam Xpress, Vetica) showed that PCAs used almost 20% less of these products in 2010-2011. Not surprising, Ketoenol usage (Movento) was up about 40% compared to 2010 and neonicotinoid usage remained about the same. The usage of the broadly toxic, old chemistry (organophosphates /carbamate/endosulfan) on head lettuce acreage continued to decline in 2010-2011, relative to the newer, selective reduced-risk products, which overall, increased considerably this season. The most commonly used insecticides in fall and spring lettuce also correspond to the key pest that typically occur throughout the season. To view a summary of the insecticide usage by chemical class over the past seven seasons, as well as the 15 most commonly used insecticides on head lettuce in 2010-2011, go to the link: Insecticide Use AZ Head Lettuce 2005-11.

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.