Pulse School: Don’t delay scouting for pea aphids

(John Gavloski/Supplied)

While you’re out scouting your peas, lentils, or faba beans for disease at early flowering, have a look for pea aphids too.

“Flowering is a good time to be scouting for aphids in peas,” says John Gavloski, provincial entomologist with Manitoba Agriculture and Resource Development. “The most damage they can do is going to occur in the very early podding stage, but we don’t want you to wait until then to do your scouting.”

You can use a sweep net or take the top 20 cm off the plant to examine them or, better yet, shake them over a tray to knock the aphids off. Then you can calculate if you’re at threshold.

For the top of the plant method, the threshold is any more than two or three aphids per plant. For the sweep net method, any more than 100 to 120 aphids per 10 sweeps is at threshold, or nine to 12 per sweep, says Gavloski.

There’s been good research behind these numbers, Gavloski says, and if the threshold has been reached, you can expect a five to six per cent yield loss due to pea aphids. Damage happens early in podding, too, which is why scouting early is so important. (more below player)

Pea aphids compete for phloem in the early podding stage of pea crops, that would otherwise go towards those developing peas. They have sucking mouth parts, so they tap into the phloem and suck it out of the plant. You’ll still get the same quality of peas, but the quantity may be reduced, and they may be smaller.

Some of the control options for pea aphids include insecticides registered for peas, lentils, and faba beans, but Gavloski says there are also lots of beneficials out there that control pea aphids. Ladybugs, lacewings, hover fly larvae, and pirate bugs all feed on pea aphids. There’s even a parasitic wasp that will attack the aphid eggs. Sometimes, if the levels of beneficials are high enough, it’s possible that they can control the aphid population.

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