CORN EARWORM

Earworm populations low in corn: What does that mean for cotton, soybeans?

My lab has searched for corn earworm (aka bollworm in cotton) from over 1,000 ears of corn this week. 

These were from hybrids that contained no Bt genes, single Bt genes, and a few were from hybrids with multiple Bt genes and decent efficacy (Optimum Intasect, and Genuity VT Double Pro, for example). 

Some folks have commented on the lack of earworms in sweet corn compared to previous years.

I happened to have a trial planted in the same location in 2012 and 2013 only four days apart, with the same hybrid, sampled on the same date (18 April). In 2012, a non-Bt variety had 28 percent ears that were infested on this date, some of which had already completed development in the ear. In contrast, this year, the same non-Bt variety had only 8 percent infested ears, with smaller-sized caterpillars on average.

So in general, it appears we will have fewer bollworms leaving corn for cotton and soybeans in late-July and August. This is another reason (in addition to others covered here) to forgo automatic insecticide applications. There shouldn’t be much to kill! There are several modifications we may need to make to our general scouting plans in both cotton and soybeans.

Corn earworm moths pupate under the soil. Timing of their emergence can be influenced by moisture. Sometimes when conditions dry up for a while, a rain event can trigger a massive moth emergence. 

Based on our weather patterns this summer, a mass moth emergence doesn’t seem likely.I predict a smaller emergence, but maybe one that is more sustained and a bit later than normal. 

Depending on where you are in the state, this might take place as early as next week (if you’re in southern North Carolina) or into August, if you’re father north.

Cotton is developing slower than usual and soybeans are still being planted. This will extend our season and give the corn earworms time to “catch up”. 

This is a multi-generational pest throughout the year. So even though few are produced in corn, more may be produced in our crops or even wild hosts (think of all the weeds we have this year!). 

I would be more concerned about this pest as time goes on, especially in late cotton and beans. If we continue on in a wet pattern, expect fewer problems. If conditions dry somewhat, expect more.