Fall Armyworm Update

Fall armyworm reports continue to come in with a wide range of crops attacked, including pasture grasses (crabgrass, Bermuda grass, orchard grass, sorghum-Sudan grass), alfalfa, clover, soybean, sorghum, and cabbage. The pest has a wide host range including over 80 species of plants.  We feel that we are dealing with the rice strain rather than the corn strain based on host plants attack. At this point, most producers are well aware of the problem across the State and are monitoring their fields regularly.  We think of fall armyworm as a tropical pest that migrates into the state each summer from its southern overwintering sites, builds up in numbers, and is killed out with the first fall frost/freeze.  While this pest cannot tolerate freezing weather, we will have to continue to manage it until that first freeze.

Figure 1. Fall armyworm has been as unpredictable as it is devastating to alfalfa, often hitting one field while leaving others a short distance away untouched. (Photo: Ric Bessin, UK)

Fall armyworm is continuing to lay eggs, and we can expect to have another generation of larvae. However, with the cooler weather, development will be slowed compared to what we had last month. As was reported last week, there is fall armyworm nucleopolyhedrosis virus active in some areas but do not expect this to give much relief.

We recommend that producers continue to monitor fields and be prepared to treat if levels approach economic thresholds.

By Ric Bessin and Jonathan Larson, Entomology Extension Specialists

Posted in Forages, General Pests, Grains
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