Has Recent Weather Increased Insect Threat?

Recent weather conditions could mean seedlings are at greater risk. ( Sonja Begemann )

Do recent cool temperatures and rainfall mean bad news for corn and soybean plants? Well, flooding and seed chilling are obvious threats, but delayed emergence or stunted growth can even impact insect threat.

“All of those pests get a foothold only when we get a cool, wet post-planting period,” said Christian Krupe, Purdue Extension entomologist in a news release. “If you don’t have those weather conditions the corn plant generally pops out of the ground and does find in terms of insect pests. So, in the early stages of the crop season [insect threat] is really weather-dependent.”

Small plants can be easier to eat and cause long-term damage. Scout for insect pests and also watch for risk factors such as weeds where insects can hide or feed before corn and soybeans emerge.

Seed pests

If your seeds have yet to emerge, watch for seed-attacking insects such as wireworms, white grubs and seedcorn maggots, according to experts at Pioneer.

  • Wireworms attack corn and soybeans and feeds on seeds, which could result in skips or wilted or dead plants if emerged, according to BASF representatives. Wireworm damage is less severe the first year you have them but gets worse in subsequent years.
  • White grubs can damage seeds or emerged plants. They’re worse in following years with high infestations of Japanese beetles as they’re the larvae form of the pest. They can be killed off in cold winters, but this past winter was mild, so don’t expect a large kill.
  • Seedcorn maggots favor cool, wet springs like many farmers experienced this year. Damage is already showing up across the Cornbelt. Click here for more information about scouting and where they’ve been found so far.

Early season pests

If you’re in no-till or weedy fields start scouting for black cutworm early. Even with traited products, damage can still occur. Corn is most susceptible when it’s under 15” tall but will recover if the growing point isn’t damaged or cut off. Look for black cutworm just below the soil.

In addition, black cutworm moths overwinter in southern states but because of the mild winter, they might not have needed to travel as far south this year. That means you might see them earlier in the season with more vigor.

While armyworm isn’t a pest you typically consider in the early season, they’re coming out in force and could be a threat. Erich Eller, owner of ForeFront Ag Solutions in Indiana, recently noted sticky traps catching four to eight moths a day—normally this time of year is two or less per day.

Threshold for spraying is 4.2 moths per day. For now, they’re eating in wheat fields, but it won’t be long before they make their way into corn fields. They can cause stand damage in early season.


Read more early season scouting tips here: