by Doug Toburen
CNHI
Parson, Kansas —
The presence of corn earworms in soybeans has been making Doug Shoup’s telephone ring lately.
“This is not something new — we get it every year,” the K-State southeast area Extension agronomist says. “It just seems like we have higher numbers than usual this year in soybeans across the state of Kansas.”
Shoup has his own hypothesis as to why farmers are noticing corn earworms — also known as headworms in sorghum and soybean pod worms, — in soybeans.
“We used to have a lot of milo and they fed on it. However, now, we have a lot of early season corn which is dried down by the time they would be feeding on it,” he explains. “So, what is left that is growing and green and lush? Soybeans.”
Although corn earworms can cause some leaf damage to soybeans, Shoup reminds producers that they need to be more concerned about them getting on the pods and chewing them off.
According to K-State research, corn earworm damage to soybeans occurs from August through September. Significant damage may occur when large larvae feed on pods consuming the developing seeds. Fields should be checked from beginning bloom for small worms.
“The threshold on whether to treat or not is one corn earworm per foot of soybean row,” Shoup says. “They are much easier to control when they are smaller — less than an inch in length.”
Corn earworms that measure an inch to and inch and a half are harder to control due to the fact that they are about done with their life cycle.
According to Shoup, there are several insecticides available to aid in the control of corn earworms.
“Just be sure to check the label for rates,” he says.
Shoup urges producers to get out and do some scouting in fields to see if corn earworms are a problem for them.
“Due to the fact we are seeing higher numbers of corn earworms we kind of need to be on the lookout for them in our soybeans,” he says. “Their pattern can be somewhat erratic and it will vary on a field-to-field basis as to whether control measures are needed.”
