Sweet corn producers in Virginia are reaching the intensive pest management period for that crop. Corn earworm is the primary pest of sweet corn, and typically very few ears will escape infestation by this pest as the summer progresses. Monitoring the activity of moths on the farm can aid in the pest management decision making. In the Northern Neck of Virginia, Parker Farms are monitoring corn earworm pheromone traps. Nightly catch of moths at the traps indicate the flight activity of the pest, potential for egg laying on the silks, and concomitant larval infestation in the ear. The Parkers have reduced the number of insecticide sprays applied to sweet corn with this information, and have obtained damage-free sweet corn over the past two years. The exact action thresholds based on moth catch can very. University of Delaware IPM provides a good table and discussion of this. Click on the following URL. http://ag.udel.edu/extension/IPM/thresh/sweetcornsg.html
In general, catch of 10 or more moths per night is high and indicates the need for a short spray interval (every 2 or 3 days throughout silking period). Less than 10 moths per night indicates that you could increase your interval between sprays. If an average of less than 1 moth per night is caught, then spray intervals can possibly be once per week. However, corn earworm moth activity increase as we progress through the summer, and in many areas of Virginia, moth catch will exceed 10 per night though most of July and August.
So far, at Parker Farms in Oak Grove in the Northern Neck of Virginia, corn earworm catch has been low in the 3 pheromone traps with the exception of one night (June 26) in one trap, when 26 moths were caught in one night. Catch dropped to 3 the following night, and has since been virtually 0. We will be reporting these trap catch data on the VA Ag Pest Advisory each week throughout the summer. We thank Raef Parker for monitoring this pest in the Northern Neck and sharing these useful sweetcorn IPM data.