Tuesday, April 16, 2013

Armyworm Flight Begins

Doug Johnson, Extension Entomologist


Figure 1. Armyworm moth
Spring must really be here as armyworm (aka true armyworm) moths have taken flight. Only a few moths have been captured thus far, but it does signal the beginning of insect season in the field crops and the current year’s capture is in line with the outbreak year of 2008. It is still too early to get real excited but important enough to be aware.
In Kentucky, armyworm can be an important pest of corn and wheat. Corn products that contain a Bt trait that provides protection from caterpillar feeding (See: Insecticide recommendations for corn:   http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf, pages 6-7) will likely be protected. However, non-Bt types including field corn refuge, popcorn, food-grade corns, and sweetcorn along with wheat will be at risk.

We are several weeks from any damage caused by armyworm as the adult moth is not the damaging stage. Monitoring this stage just gives us a “biofix” or heads-up that the pest is about. It is the caterpillar in which we are interested. You may want to check the flight graphs each week for the progress in this population. These may be found at:  http://www.uky.edu/Ag/IPM/ipm.htm. It only takes a few seconds to check and this can give you an idea of the relative risk of this pest for this season. On the graph you can see displayed the current year’s capture (green), the rolling five-year average (blue), and known populations that have resulted in outbreaks (red and/or black) This will give you a rough estimate of the current year’s relative risk. As these graphs represent moth flight, the relative population size can be seen before the damaging stage, the caterpillar, develops.

If populations appear to be indicating an elevated risk, I will use a temperature-based model to predict when the caterpillar stage will appear. This model will NOT predict which fields will be infested. One must scout fields to know if the armyworm is present, but the model will provide an estimate of when the field should be scouted. Remember, the model predictions will be based on the capture and temperatures at the UK-REC in Princeton (Caldwell Co.) KY. In areas to the south and southwest of the UK-REC caterpillar development will be ahead and areas to the north and northeast of the UK-REC will be a bit behind.  I will post, and you may review, the results of these model runs each week in this publication. So, if you are the pest manager for wheat or corn this spring, keep yourself tuned to this outlet for “Early Warnings” about this pest.

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