The weather remains warm and we're not out of danger from most fall insect pests. However, as temperatures begin to cool down in the next week or so, it is important that you not forget about Liriomyza leafminers, particularly as the first produce fields approach harvest. Leafminer numbers have been light-moderate thus far this season, but we have recently observed higher numbers (adults and larvae) showing up on the older leaves of lettuce here at the Yuma Ag Center. Much like last season, an increase in adult flies has been observed on yellow sticky traps used for monitoring whiteflies over the past week or so. In most cases, these traps have been located near or adjacent to fall melons, cotton or alfalfa. With temperatures forecasted to be in the 80 and 90s for the next week, leafminer adults should continue to be active, and larval activity could easily cause damage if left uncontrolled in lettuce or baby leaf fields where they are currently present. These larvae can cause significant damage to older, pre-harvest lettuce by feeding and damaging wrapper leaves of head lettuce and romaine. Pupae collecting within the leaf margins can also be considered contaminants. In addition, baby leaf lettuces, spring mixes and spinach are susceptible to larval feeding (mining) on the tender growing leaves. These populations can be effectively controlled with currently available products. Products that are presently being used to control armyworms, loopers and thrips such as, Radiant (5-7 oz/ac), Coragen (5-7 oz/ac) and Voliam Xpress (9 oz/ac), can effectively kill newly emerged larvae in the leaf mines before they cause significant damage. Similarly, Agri-Mek at 8-12 oz/ac can provide long residual control. Be sure to include a penetrating adjuvant with these products to enhance translaminar movement of the product and larval control. For more information on leafminer biology and management please go to "Leafminer Management".

Remember: When in Doubt-Scout.

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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.