Who would try to infest their corn with insects on purpose? Mark Lawson would. He's an agronomist with Syngenta, and he inoculated small plots on his farm where he conducts research. The purpose in this case was to demonstrate the value of planting Agrisure Viptera corn. It will be available in various hybrids for next spring.
Coupled with BT traits for corn borer and rootworm, it picks up other pests some events aren't as strong on, including black cutworm, dingy cutworm, fall armyworm and earworm.
What Lawson found is that sometimes it's difficult to make insects infest corn even when you want them to. Weather interfered, primarily a heavy rain on the night of each time he inoculated silks. Still, he has some insect pressure in his plots, especially from corn earworm. During an inspection trip, a tiny earworm larva was found on a Viptera ear, but there was no feeding. The insects must ingest a tiny amount of the proteins inside the plant that kill the insect before they'll die.
For this Agrisure Viptera plant, it's expressed in multiple parts of the plant, Lawson says. That means that if the insect eats on the silks or tried to nibble a bit out of a kernel, the tiny dose it gets should prove lethal.
In areas where rains didn't bail out the plants from insects, and even though plants weren't inoculated, there are reports of insect presence in the Corn Belt. Western bean cutworm is particularly nasty, since it opens up four to five holes in one ear, eating through the shuck into the kernels, exposing the ear to all kinds of pathogens, plus water form rains. That leads to quick sprouting of certain kernels within the ear.
Many fields are past the point where spraying would be economically feasible for insects. Besides, insects such as corn borer and corn earworm move into the stalk rather rapidly, Lawson notes. Once they're into the stalk and out of view, they won't be affected by chemical applications.
The best bet now is to scout fields to see where stalk rots might develop first, or to a more severe level. Insect feeding leaves perfect channels for ear and stalk rots to invade if conditions are favorable. Field which fail the push or pinch test, whereby you go down the row and push over or pinch tissue in every stalk within a set distance, should be marked for early harvest.