Crop Scene Investigation - 21 Solved: What's the pest plaguing Jim's corn field?

Sunday, January 10, 2010

by BERNARD TOBIN

The pests feeding on Jim's corn crop were millipedes. "In this case it's important to remember that millipedes are classified as pests, not insects," explains Ontario Ministry of Agriculture, Food and Rural Affairs entomologist Tracey Baute.

"There was a history of wireworm in that field and the grower was correct to treat the field with Poncho," recalls Baute. "Seed treatments like Poncho and Cruiser are very effective in protecting the seed against insects but the millipede is not an insect and is not affected by the seed treatment." She notes it's extremely rare to see millipedes in the soil early in the season attacking corn seed.

"Millipedes are quite common, but most often they're a beneficial arthropod. That's why we had to do a bait test to confirm it wasn't wireworm that was doing the damage," says Baute.

Baute is uncertain whether millipedes will become a significant problem for corn or other crops. "Growers are planting earlier, into cooler and wetter soils. That means the seed is sitting there for a longer time and I can't blame the millipedes for going to a sugary substance in the soil."

In Jim's case, not much could be done to rectify the problem. When it comes to controlling pests and insects, Baute says growers who farm sandy loam soils are often at risk. Her control recommendations include using seed treatments, effective burndowns and in some cases tillage, to eliminate host environments which sustain pest and insect populations.

Congratulations to Frank Dietrich, Lucan, for his correct answer. BF