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23
Jul
2015
Headworms Infesting Grain Sorghum
Author: Glenn Studebaker, Extension Entomologist

Earworm on sorghum
Photo by Kevin Lawson

Dr. Glenn Studebaker, Dr. Gus Lorenz and Dr. Nick Seiter

We are picking up headworms in grain sorghum all across the state. We are seeing all three species (corn earworm, fall armyworm and sorghum webworm) in some fields. Corn earworm and fall armyworm appear to be the predominant species in most areas. We are seeing up to 10+ per head in some fields in south Arkansas. Treatment threshold for corn earworm and/or fall armyworm is 1 or more worms per head. Worms should be 1/2-inch or longer before considering treatment. There are a lot of predatory insects out there and these often take out smaller worms, but once they reach 1/2-inch in length the caterpillars have a much better chance for survival. Treat for sorghum webworm when five to six per head are found. If a field is at treatment level, Blackhawk, Prevathon, Besiege, Belt or Lannate would be recommended for control. Consult MP144 Insecticide Recommendations for Arkansas for a complete list of recommended insecticides and rates. If sugarcane aphid is in the field but still below treatment level, use an insecticide that is soft on beneficial insects such as Blackhawk, Prevathon or Belt. Stay away from harsh materials like Lannate or Besiege in order to avoid flaring aphid populations.


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