Aphid Management on Lettuce Using Soil and Foliar Insecticides (November 13, 2013)

In last week’s update, we noted that PCAs would soon begin finding aphids infesting local lettuce and cole crop fields. As predicted, we have received reports from two PCAs that small colonies of wingless aphids have been found on lettuce, along with winged adults. These populations have been found in both the Yuma Valley and Wellton; we’ve also found winged green peach aphid at YAC. Timing of aphid colonization in leafy vegetables varies by species, and depends largely on temperature, rainfall and planting dates. However, my experience over the years, as well as observations from numerous field trials, suggests that aphid species that infest leafy vegetables are historically most severe on crops planted from mid-November through December. Of course, there are exceptions to the rule and aphids can occur when least expected. Consequently, you should begin planning now for spring aphid management. Growers and PCAs have effective options for aphid management on spring leafy vegetable crops. First, there is the responsive approach that relies on foliar insecticide sprays to reduce aphid numbers when they are found on crops. A number of insecticides are available that have cost-effective activity against aphids when applied as foliar sprays targeted at aphid populations as they begin colonizing plants. There is also the preventative approach where growers can apply neonicotinoid insecticides at-planting, 1.5 to 2 inches below the seedline. The insecticide is taken up by the plant roots, systemically translocated throughout young plants for several weeks following emergence, and ultimately prevents aphid colonization early in plant development. Both approaches can be very effective, and both can be used on the same field. Among the neonicotinoids, imidacloprid has been the standard soil insecticide applied on spring lettuce for aphid control for 20 years and continues to provide long residual control when used properly. More recently, Movento, with its excellent systemic activity against aphids via foliar application, has been incorporated into lettuce IPM programs along with other novel insecticides with aphid activity. Other effective foliar options include Beleaf, Assail and the newly registered Closer. However, the question has recently been posed: Which approach to aphid management is better? Our research suggests a combination of both; imidacloprid applied at planting, followed by foliar insecticides if needed under heavy late season pressure. For more information on this topic please visit the research report - Aphid Management on Head Lettuce Using Imidacloprid and Foliar insecticides.