Louisiana's Weird Corn Year Continues

This has been a weird year for Louisiana corn.

First, some corn had enough spider mite pressure that it had to be treated. Off hand, nobody we spoke with could ever remember that happening in the state. Treating mites in corn is fairly common in arid parts of the country, like California's San Joaquin Valley where growers typical spray mites on corn in areas that receive little or no rain during the season.

Through much of the spring and into the summer, parts of Louisiana actually received less rain, in fact, than areas around, say, Bakersfield and Fresno in California.

Louisiana's cropping season and surrounding landscape were thrown out of whack early. Winter and early spring rains kept vegetation growing and also shut farmers out of the field when they needed to do prep work. All that likely gave pests a chance to build in wild hosts, both inside and on the edges of fields

Then as the extended dry period gripped the state, temperatures rose sharply and have lingered in the high 90s to low triple digits since late May.

If there was going to be a year to treat spider mites in Louisiana corn, this would have been it.

And now farmers and their crop advisers are facing the reality that corn has also taken an economic hit from corn earworms, something that nobody would have thought possible.

The pest typically nibbles away at the tip of the cob, which produces kernels that never quite make it through the harvesting process, anyway, because of their size and odd placement on the tapering ear.

This year, though, that part of the cob was mostly blank due to heat-induced pollination problems. Plus, a larger-than-normal earworm moth flight developed early, putting more pressure on the crop. When worms couldn't find small, tasty kernels on the cob's tip, they moved down the cob and at into kernels that actually are bigger, valuable and harvestable.

"Where we might only see one worm in a cob – mainly because they tend to eat competing worms when they find them on the tip – we found cobs with 2 or even 3 worms," said Roger Leonard, LSU Research Entomologist. "Instead of sitting on the tip but, they moved down the cob on different sides and never bumped into each other. When we have any kind of injury, it tends to be late when we higher persistent pressure and more larvae in there."

Leonard said he had never seen this happen before and didn't think that it was possible to sustain economic loss like this on any kind of scale.

"This was turning up in the Yieldgard and Herculex corn, as well as hybrids without those traits," he added.

As not to leave soybeans out, brown stink bugs are turning up in some soybeans, mainly in south-central Louisiana. But these aren't the regular brown stink bugs, though some probably are in the mix.

Several stink bugs kind of get lumped into the "brown" category, although the one commonly called "brown" is the one that tends to be an annual problem.

"There are at least 2 species out there where we're dealing with them right now -- our regular brown and a somewhat smaller one that is kind of around but hardly ever in big numbers," Leonard said. "It's not common enough that it's been given any kind of common name. They’re both managed the same way and need to be treated when they hit action thresholds. More and more fields there are being treated.”

- Owen Taylor