August 28, 2007

 

South Dakota aphid population seen up, may hurt state's soy production

 

 

A soybean entomologist says the aphid population is expected to rise again this year.

 

Kelly Tilmon of South Dakota State University (SDSU) in Brookings said the rise probably won't match last year but that another spike is anticipated.

 

The small insects can cause significant damage by sucking the sap from soybean plants. Untreated, aphids often trim farmers' yields.

 

Last year, the number started to increase before peaking in mid-August.

 

While aphids were a big problem last year, they're only appearing in one of every four or five SDSU test plots this summer, Tilmon said - with most surfacing in southeast South Dakota.

 

"It's a little bit dangerous to make generalizations about a whole region because they might not pertain to a particular producer," she said.

 

The treatment threshold for aphids is 250 per plant over at least 80 percent of a field. If that is met, SDSU advises an insecticide application within seven days to salvage as much yield as possible.

 

Once soybeans reach the full seed stage, there is no SDSU research to indicate that treatment will increase yields.

 

Tilmon warned that one soybean field can be infested with aphids while another nearby field might show no problems.

 

Why aphids are so random and why they can be so different from year to year is a bit of a mystery, she said. SDSU and other universities are conducting research, but there aren't many answers yet, Tilmon said.

 

Farmers need to check for infestations by examining 20 to 30 plants per field from 10 different locations within the field, Tilmon said.