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Spraying for aphids can backfire
DES MOINES (DTN)--The memory of 2003 for farmers having to fight soybean aphids may cause spraying for the pests too early this year, not allowing natural predators to work, said Kevin Steffey, a University of Illinois Extension entomologist.
By spraying too soon, he said, farmers would negatively affect the natural predator's ability to control aphids.
"We are saying make sure they are aphids first off. Don't spray until the number of aphids is at a threshold level," Steffey said. "It takes 'x' number of bugs to cause economic loss, so spraying early is a waste of money."
Aphids, which are a piercing sucking insect, feed on all parts of plants. They pierce the leaf surface and suck out nutrients and secrete carbohydrates for sugars, which causes the plant to turn black. The stunting of the plant starts to produce fewer pods.
Perhaps the biggest problem is aphids can double their population on a plant in just two days.
Last year, Illinois farmers sprayed between 750,000 and 1 million soybean acres after an aphid outbreak. This has caused farmers to be understandably "gun shy" this planting season, Steffey said.
"We have aphid experts looking but not finding any," he said. "People that have had aphids in the past are finding nothing in Illinois."
One Illinois farmer has reported a possible sighting of aphids, but it has yet to be confirmed.
The concern about aphids started when a field in southeast Iowa reported 150 to 250 aphids per plant earlier this week. So far, this is an isolated incident.
Mark Carlton, an Iowa State University crop specialist in southeast Iowa, said the report of a high number of aphids was surprising.
"The key is just for farmers to get out into their fields and look for aphids," he said. "If they find aphids, go back to that field a few days later and watch for higher populations."
Other locations in Iowa have reported no or very few aphids, said Palle Pederson, a soybean specialist at Iowa State.
"I know a lot of people are talking about it (aphids) but not very many have been found," he said. "We are watching them very carefully. We want to inform, not scare farmers. They may be there, so start scouting now."
Pederson said growers shouldn't panic and start spraying just yet.
"We are telling farmers, don't mix insecticides into the roundup just because of one reported incident in southeast Iowa," he said.
While scouting their fields, farmers who find threshold levels of aphids should spray early to reduce yield loss. Last year, Illinois farmers who sprayed early saved 10 bushels an acre while spraying later saved only five bushels an acre.
"In this case, spraying early doesn't mean before threshold levels," Steffey said.
Date: 6/24/04
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