. . . . . Scout for Corn Leaf Aphids Now . . . . . In Soybeans, Make Sure to Use the Scientific, Research-Based Soybean Aphid Economic Thresholds . . . . .

Scout now for corn leaf aphids       

Corn leaf aphids are an emerging insect pest of Bt-corn and conventional corn in South Dakota.

A recent study from Europe indicated that corn leaf aphids may be more numerous on Bt-corn
than conventional corn:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000600

Corn leaf aphids have syringe-like mouthparts and feed on the sap of corn; when numerous, they
can cause wilting and can severely interfere with pollination, resulting in “barren” corn ears at
harvest.  Injuries to corn occur during or immediately before pollination, so timely scouting and
treatment are crucial.

A procedure for calculating economic thresholds to include current or predicted corn market
value, cost of controlling the insect, and yield potential is available at:

http://www.ipm.iastate.edu/ipm/icm/1998/8-10-1998/cornaphids.html.

For example, at $7 per bushel corn, 150 bushel per acre yield potential, $10 per acre control cost,
and normal moisture conditions, spraying would be cost-effective even if only 3 percent of the corn
plants are covered with aphids in the tassel.

Insecticides labeled for use against corn leaf aphids in South Dakota are Asana, Capture, Cobalt,
Delta Gold, Hero, Lorsban 4E, Mustang Max EC, Penncap-M, Proaxis, and Warrior.  Read and
follow label directions before using pesticides.

 

Soybean aphids in high numbers in most areas        Commentary

Reports from coops around the state indicate that the soybean aphid is in high numbers in most
soybean growing counties.

I have never seen this high number of soybean aphids this early here in Brookings; I just got
done spraying our plots (in R2 stage) today July 28, 2008.

Make sure to use the correct research-based economic thresholds (Commentary):

Soybean Aphid Stage-Specific EIL

You can also find a new list of soybean aphid insecticides from my Web site at:

http://plantsci.sdstate.edu/ent/entpubs/sa_insecticides.htm

Call or e-mail me for any questions.


New! Continuing Education: Impact of Aphids on Soybean Yield Components

 

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 Web Posted on Thursday, July 10, 2008 by Mike Catangui. Last Updated on Monday, July 31, 2008.