Corn School: Managing corn rootworm above and below ground

Corn rootworm can be a major yield-robber and this year more than most, it’s on everyone’s minds.

Amanda Craven, agronomist at PRIDE Seeds is joined by Bernard Tobin for this Corn School episode to talk resistance management, how rotation helps, and how corn rootworm affects yield.

“What we’re seeing this year, in our corn-on-corn fields, where we had above-ground protection only, we are seeing a lot of goose-necking, we saw some root-pruning earlier on, and now we’re seeing large numbers of adult corn rootworms, in some situations both northern and southern,” says Craven.

Craven says that as of now, in Ontario, the above- and below-ground traits are holding up, but the big conversation is around how to keep efficacy of those traits.

The proof is in the plots — all of the symptoms Craven mentioned before, are noticeable in corn on corn trials. Larvae feeding early on, goosenecking, root pruning, and in the video, the differences are night and day in G2 (above-ground protection) and G8 (above- and below-ground protection).

Yield losses from goosenecking are clear, and research on root pruning effects on yield, predict that something as small as one node is lost, can be a loss of 15 to 18 per cent yield loss in the plant.

“Although what’s lost is lost at this point, it’s important to be able to walk into the field and try to understand what’s going on today, so we can track that through the next few seasons, to see if the technology is holding,” says Craven.

Craven recommends to scout now using sticky traps, to look for both southern (yellow and black striped) and northern (bright green) corn rootworm adult beetles.

If corn was planted on corn with the appropriate variety with above-and below-ground protection, for adults or root pruning. If adults are present, that’s a big problem, she says, and it’s a concern going forward that indicates resistance.

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