Wheat School: Scouting for wireworms as they start to wiggle in to the crop

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With over 30 species of wireworms across the Prairies, the chances of you seeing some in the springtime are pretty good.

For the most part, it does get narrowed down into three main species of wireworms that seem to cause the most issues in our cereal crops: the bicolor, the destructor, and the californicus.

Lyle Jensen, agronomist with AgroPlus Inc., says that the destructor tends to be the largest of the three, whereas the californicus and the bicolor tend to be a bit smaller.

When scouting for wireworm damage, Jensen says you are going to be looking mostly for the above ground symptoms first, before you start digging.

“In wheat, that’ll generally be either laying over flat on the ground, or it’ll be wilting compared to others around it, or just dead and shrivelled up,” he explains. Where things start to get sticky though, is control options, as thresholds are pretty difficult to establish in this situation.

“Prior to seeding, you’re probably going to spend a lot of time digging fruitlessly in the ground and not finding a whole lot. So trying to predict what’s going to happen in any one field with wireworms is next to impossible. So the only tool that we really have to fight them is seed treatments. And traditionally, we’ve been relying on neonics,” Jensen says. “And those at best give you suppression for 30-35 days, just to allow the crop to kind of grow past the really damaging stage of emergence before the wireworm starts feeding again.” (Story continues below video)

Obviously if the plants are coming out of the ground, it’s too late for seed treatments. Does that mean we don’t need to scout? No, because the knowledge of what is there, and keeping record of it, can help us significantly going forward. One way to do this, is to pay attention to click beetle populations, the adult version of the wireworm.

“You can use click beetle traps, which are dug into the soil. The beetles just kind of blunder into them and fall into a pit. And if you go and check those every week, and count, you’ll be able to establish somewhat of a threshold for that area. And if the populations are really high, you’re probably going to be at risk the next year,” Jensen says.

When it comes to final yield tolls, the damage from wireworms can be quite significant.

“They can be really devastating,” Jensen explains. “I’ve found several fields over the years where sometimes populations can be six to eight wireworms in a foot of seed row, and that can reduce your plant stand by 60 to 80 per cent, or more. Every year, somewhere in southern Alberta, there’s fields that get reseeded because of wireworms.”

Check out more Wheat School episodes, here.

 

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