The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona Cooperative Extension in Yuma, Ariz.

Leafminer management on fall lettuce

By John Palumbo, UA Research Scientist and Extension Specialist

Although the hot weather is beginning to break in the desert, pest control advisers should not be complacent in leafminer management. Leafminer numbers have been light over the past few years. We have recently observed unusually high numbers (adults and damage) on melons and lettuce particularly in the Yuma Valley.

Yellow sticky traps used for monitoring whiteflies throughout the area have been almost covered with leafminer adults over the last few weeks. These numbers have been generated from melons and cotton.

With temperatures forecast in the mid-80s and 90s for next week, leafminers adults will be looking for a good host plant. Many leafy vegetables serve as ideal host this time of the year.

If left uncontrolled, leafminer populations can rapidly reproduce under these weather conditions and cause significant damage to older, pre-harvest lettuce by feeding and damaging wrapper leaves of head lettuce and romaine. Baby leaf lettuces, spring mixes, and spinach are susceptible to larval feeding (mining) on tender growing leaves.

This can be effectively controlled with currently available products. Radiant, Coragen, and Voliam Xpress applied at higher rates can effectively kill developing larvae in the leaves before causing significant damage. Similarly, Agri-Mek at 8 ounces or greater can provide long residual control.

For more information on leafminer biology and management, click on this link.

Contact Palumbo: (928) 782-3836 or jpalumbo@ag.arizona.edu.