Some sorghum fields across the Mid-Coast of Texas have been inundated with Rice Stink Bugs or Headworms; or in some cases, both stink bugs and headworms. Adding to this problem, I have received several reports of pyrethroid insecticides failing to control rice stink bugs.
Scout sorghum using a 2-gallon bucket and beat heads into the bucket and see what is being captured in the bucket. Look here for a brief video.
Economic thresholds for stink bugs and headworms depend on the cost of control, expected crop value, and sorghum heads per acre. Look here for an economic thresholds calculator.
I am using an economic threshold of 0.5 – 1 stink bug per head, depending on heads per acre.
For an economic threshold for worms, divide them into medium larvae (1/4 to 1/2 inch) and large worms (>1/2 inch). treat when the field averages more than 1 medium worm per head or 1 large worm in 5 heads. Small worms under 1/4 inch no not need to be considered as they feed very little and natural mortality is very high.
For control of Rice Stink Bugs I typically recommend the pyrethroids. But with this week’s reports of local field failures, I suggest using Dimethoate, Stallion or Cobalt Advanced.
Suggested insecticides for corn earworms include Prevathon, Beseige, Lannate, Blackhawk, Stallion, Cobalt Advanced and pyrethroid insecticides.
Following treatment for stink bugs and/or headworms, watch for Sugarcane Aphid populations to increase. This may occur after and insecticide application reduces the beneficial insect numbers.