Heavy populations of chinch bugs have been detected in some area corn fields. An average of three to four chinch bug adults are being commonly found on many corn plants.
The economic threshold is reached when two or more adult chinch bugs are found on 20 percent of seedlings less than 6 inches tall.
Larger plants can tolerate a few more chinch bugs but chinch bugs are capable of causing significant damage to plants up to 18 inches tall. On plants between six and 18 inches tall, treatment should be made when chinch bugs (adults and nymphs) are found on 75 percent of the plants.
Symptoms of feeding may appear as reddening of the stalk and foliage. Heavily injured plants may appear stunted and show symptoms of drought stress. In extreme instances, plants may fall over from extensive root feeding.
The best defense against chinch bugs is an insecticide seed treatment (Prescribe) or a full rate of a soil insecticide at planting (Counter 15G @ 8 oz./1000 feet, Counter 20CR @ 6 oz./1000 ft. or Lorsban 15G @ 8 oz./1000 ft.). Reduced rates of Counter or Lorsban will give some chinch bug suppression but may fail under heavy pressure.
A grower recently asked me if Gaucho treated corn is the same thing as Prescribe treated corn. Both treatments contain the active ingredient imidacloprid but the Prescribe treatment has over 8 times the concentration of the Gaucho treatement.
Gaucho treated corn should be checked carefully for the presence of this pest as the rate of active ingredient may be too low for adequate control.
Now that I have a problem, what can I do? The best “rescue” program is a directed spray at the base of the plants using at least 20 gallons of water per acre. Coverage is even more important than your choice of insecticide. The spray material must come in direct contact with the insect for effective control. Broadcast sprays will be ineffective - the directed spray is the only way to go.
As far as materials go, the cheapest alternative would be one of the labeled pyrethroids (Fury, Warrior T). Other choices include Lorsban 4E and Sevin. A rescue treatment will “buy” protection for about a week to ten days, usually enough time for the crop to outgrow the problem.
Chinch bugs prefer corn but they also like grain sorghum. We have no local reports on sorghum infestations but I expect them in the foreseeable future. A similar program (directed spray) is suggested as a rescue treatment in grain sorghum.
Gaucho treated grain sorghum is not the same as Gaucho treated corn. Gaucho treated grain sorghum has four times the concentration of imidicloprid as Gaucho treated corn.