Rootworm creates challenges

One of the hottest coffee shop conversations all winter was about the coldest weather Iowa has had in two decades. “As much as we’d all like to find a silver lining in this situation, chances are corn rootworm populations won’t be deterred,” says Nick Benson, corn product specialist with Latham Hi-Tech Seeds. “Instead of throwing caution to the wind, farmers need

Rootworm creates challenges

One of the hottest coffee shop conversations all winter was about the coldest weather Iowa has had in two decades. “As much as we’d all like to find a silver lining in this situation, chances are corn rootworm populations won’t be deterred,” says Nick Benson, corn product specialist with Latham Hi-Tech Seeds. “Instead of throwing caution to the wind, farmers need to take an aggressive approach to managing corn rootworm larvae during the upcoming growing season.”

No one factor should be solely blamed for the increasing corn rootworm problem, as that can limit your management options and ability to combat the threat, he says. Growers need to address their corn hybrid trait rotation, yet not ignore other factors like scouting and crop rotation. Rotating traits is important, but it isn’t the only solution. Traits help protect plants, but rootworm larvae may still cause damage. Larval feeding hinders a plant’s ability to absorb water and nutrients, and affects its ability to develop and remain upright.

Protect your 2014 crop from these yield-robbing pests. Benson suggests the following steps as you develop a plan to protect your plants, yield and profit.

Scout your fields. Check what’s happening both below- and above-ground. Notice what’s going on below the ground by scouting for larvae. Come late May, at the same time lightning bugs begin to light up the night, larvae will begin to hatch.

Once silking has or is about to begin, observe what is happening aboveground. Adult beetles feed on the corn ear, silk or tassel. You can also identify corn rootworm by “window paning,” which occurs after the beetles emerge and begin eating leaves on the corn plant. This can be extremely damaging to corn plants because of the role the leaves play in photosynthesis. Late-planted corn is especially at risk for window paning, so if identified, insecticide should be applied.

Root digs are crucial to help you make management decisions. The data you collect will tell you more than you could imagine compared to past field data. Also, take last year’s crop performance into consideration. If your field is high risk for a corn rootworm infestation, consider alternative traits,refuge in a bag, or RIB, options and possibly even rotating in another crop, such as soybeans or alfalfa.

Understand rootworm cycle. Western and northern corn rootworms deposited their eggs last autumn, but it won’t be until late May or early June when newly hatched larvae begin their feeding frenzy on corn roots. Male rootworms will emerge first in late June to early July, with females following about a week later. Peak egg laying will begin in early August.

In recent years, controlling corn rootworm has become continuously challenging for a number of reasons. More farmers are planting continuous corn and more are relying solely on genetic trait protection, which is often not providing the desired results. And corn rootworm is adapting. The northern species uses a tactic called extended diapause, which allows its eggs to lay dormant during the time fields are in soybeans.

Corn rootworm eggs will then hatch after the field is planted to corn, and the young worms will feed on corn roots.

Adult CRW females have learned to lay their eggs in soybean fields, thereby allowing them to hatch the following spring when the field is planted to corn. With these changes in what used to be considered the “normal” life cycles of rootworms, it may become necessary to rotate the field out of corn for two seasons.

Respect the refuge. Managing CRW requires increased diligence including planting refuge acres. “Not only is planting a refuge each grower’s responsibility, a refuge is also our best chance to keep rootworm traits viable for the future,” says Benson. “Refuge-in-the-bag options are easy as they combine refuge seed with both the corn borer and rootworm insect protected corn seed. Corn growers have everything they need to be refuge compliant in just one bag.”

Corn rootworms essentially need corn to survive, so volunteer corn counts. Because volunteer corn and pollen-producing weeds attract these pests, both must be controlled. It’s advised that you apply a tankmix treatment and clear any volunteer corn to help avoid the harboring of rootworm beetles in your bean field. With herbicide use and careful crop planning, generally volunteer corn can be controlled in both corn and soybeans.

“Management of corn rootworm is a complex issue and the solution is more than just traits,” sums up Benson.

“There are many factors and management options you must consider, including scouting fields, understanding rootworm cycles and using best management practices. By being informed and prepared, you can be successful in keeping corn rootworm from devastating your crop in 2014.”

For more information, visit www.lathamseeds.com.

Source: Latham Hi-Tech Seeds

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PRUNED ROOTS: Corn rootworm is an increasing problem for farmers who grow continuous corn.

This article published in the March, 2014 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2014.

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