Corn rootworm larvae get top billing when it comes to insects chewing corn roots.
What you may not know is that corn rootworm isn't the only pest that can cause enough root damage to affect yields. Corn nematodes fall in that category. So does grape colapsis. Their damage is more sporadic, but it can be intense.
Here's what the panel of Indiana Certified Crop Advisers says you ought to know about this pest.
Question: My neighbor claims he lost corn stand to grape colapsis last year. I've never heard of it. What is it? Should I treat for it or just take my chances?
Andy Like, Daylight Farm Supply, Evansville: Grape colapsis is a small grub 1/8th to 1/16th inch long that feeds on the surface of secondary corn roots. Feeding generally stunts emerging to V7 corn plants, and gives them a scorched appearance.
Investigate your neighbor's problem more before implementing control measures. If you do need to control it, use a preventive treatment. No rescue treatments are available. The majority of seed sold comes with some type of treatment. It's likely you're already unknowingly controlling it by planting insecticide-treated corn. If you don't plant insecticide-treated corn, several soil-applied insecticides are labeled for control.
Tom Stein, Ceres Solutions, Templeton: Grape colapsis has one generation per year. It matures into an adult resembling a brown corn rootworm beetle. Feeding injury on corn leaves and silks has not been found to be economically significant.
Most injury from grape colapsis in recent years has been to seed corn. Their populations are consistent in fields for a number of years. A field that was damaged should be considered at risk for future damage.
A new tool we have for this pest is Poncho/Votivo seed treatment. It employs a systemic agent that's absorbed by new roots, along with a biological mode of action form a unique bacteria strain that lives and grows with young roots. This creates a living barrier that prevents many secondary pests, including grape colapsis, from causing damage. This dual mode of action results in a more uniform and healthier plant establishment.
Greg Kneubuhler, G & K Concepts, Harlan: These grubs are much smaller than Japanese beetle grubs. In the fall, grape colapsis moves deeper in the soil and overwinters there. History has shown that they follow moisture in the soil. In drier years populations tend to drop significantly for the following year.
Historical scouting from last year may provide insight as to whether they're on your farm. Getting the crop off to an early, rapid start can 'outgrow' their feeding and damage to some extent.