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Corn Rootworm Larval Hatch Underway

Too soon to evaluate insecticide effectiveness.

Tom Bechman 1, Editor, Indiana Prairie Farm

June 9, 2010

2 Min Read

On June 1 right before dark my wife, Carla, noticed a couple of fireflies out in the yard as we sat on the back porch after helping the kids complete 4-H chores for the evening. My thoughts immediately turned to …corn rootworms!

While it may seem like a strange connection, many entomologists still believe the appearance of lightning bugs and the detection of the hatch of the first corn borer larvae in the spring correlate fairly well. You decide whether it's a wives' tale or the truth. What is know is that certain insects take a fairly specific number of growing degree days to develop before larvae hatch. If the two insects require about the same number of growing degree days to reach these perspective forms of development, it's a plausible theory.

Sure enough, last week's Purdue University Pest & Crop Newsletter issued weekly during the season by the Purdue Entomology Department brought news that entomologists at Purdue officially found rootworm larvae on corn in Tippecanoe County on May 29, just a few days before we saw our first lightning bugs in the yard.

Rootworm hatch has occurred as early as May 15 In Indiana, specifically in Tippecanoe County, most recently in 2000, and as late as June 11-12. The late hatches were features of the 1990s. The latest hatch recorded this decade is June 4 in the 2006/2007 time frame.

What you need to know now is what to expect once rootworm larvae have hatched. If you planted rootworm –resistant corn in all fields, you should be protected. If you applied a soil insecticide, you'll have to wait and see how well the insecticide works over the next few coming weeks.

Root digs will eventually reveal how well rootworm larvae were controlled. But it's too early to start digs yet, entomologists note. With the hatch of May 29, they look for digging of roots to reveal what they need to know if done sometime during the last half of June.

If you're counting on the cold winter to have wiped out rootworms where you didn't use Bt corn and didn't apply an insecticide after soybeans or corn, you may be assuming something not based on fact. Purdue Extension entomologists John Obermeyer and Christian Krupke, claim rootworms tend to survive cold winters fairly well.

What's more critical to the amount of infestation you might see this spring is weather during the next couple of weeks, they note. If heavy rains develop in early June, rootworm larvae may not be successful, they note. It's a much more important factor than the weather during the winter.

About the Author(s)

Tom Bechman 1

Editor, Indiana Prairie Farm

Tom Bechman is an important cog in the Farm Progress machinery. In addition to serving as editor of Indiana Prairie Farmer, Tom is nationally known for his coverage of Midwest agronomy, conservation, no-till farming, farm management, farm safety, high-tech farming and personal property tax relief. His byline appears monthly in many of the 18 state and regional farm magazines published by Farm Progress.

"I consider it my responsibility and opportunity as a farm magazine editor to supply useful information that will help today's farm families survive and thrive," the veteran editor says.

Tom graduated from Whiteland (Ind.) High School, earned his B.S. in animal science and agricultural education from Purdue University in 1975 and an M.S. in dairy nutrition two years later. He first joined the magazine as a field editor in 1981 after four years as a vocational agriculture teacher.

Tom enjoys interacting with farm families, university specialists and industry leaders, gathering and sifting through loads of information available in agriculture today. "Whenever I find a new idea or a new thought that could either improve someone's life or their income, I consider it a personal challenge to discover how to present it in the most useful form, " he says.

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