AgEBB-MU CAFNR Extension

David Burton
Civic Communications Specialist
2400 S. Scenic Ave.
Springfield, MO 65807

September 1, 2017

Field Crop Scouting Report:
Aphids and Armyworms Found in Southern MO Counties

LAMAR, Mo. — Jill Scheidt, agronomy specialist with University of Missouri Extension, scouted fields along west of Lamar for the Aug. 16 crop scouting update.

Printed reports are sent out one week after the report to allow subscribers to phoned reports the full benefit of their subscriptions. Barton County MU Extension sponsors the field scouting report. For more information on the scouting report, or to learn how to receive the information earlier by telephone, contact the Barton County Extension Center at (417) 682-3579.


Corn was in the maturity stage.

Corn should range from 23-25 percent moisture before harvesting. According to Iowa State University Extension, cost of artificial drying can be significantly reduced by waiting to harvest until 15-20 percent moisture. Weather conditions can affect dry down time.

"If weather is cool, a decrease from 30-20 percent moisture could take as much as two weeks and stalk quality can degrade quickly, so harvest before stalks begin to degrade to avoid harvesting loss," said Scheidt.


Soybeans ranged from fourth trifoliate to full seed stage.

Scheidt did not observe podworms but saw quite a few green cloverworm.

Green cloverworm are mainly defoliators. Differentiate between larvae by counting prolegs located in the middle of their body. Green cloverworms have three prolegs and podworms have four prolegs.

"Green cloverworms were defoliating some fields in the full seed stage to around fifteen percent," said Scheidt.

The threshold for any foliage-feeding insect is 30 percent defoliation before bloom and twenty percent defoliation during or after bloom. The threshold level for pod feeding insects including, podworms and stink bugs is one per foot of row or when five percent of pods are damaged.

"Stink bugs have piercing-sucking mouthparts, look for bruises and dead areas on pods instead of holes. Late planted, and double crop soybeans are at greatest risk for podworm damage," said Scheidt.


Milo was in the heading stage.

"Quite a few sugarcane aphids were seen on some plants, but not at threshold level," said Scheidt. "Scout on the underside of the leaves for small yellow aphids. Once aphids are seen, scout milo daily as populations can increase rapidly."

The threshold for headed milo is 750 sugarcane aphids per plant, according to University of Missouri Extension guidelines. Reports of threshold level aphids have been reported in Stone County.


"Fall armyworm feeding has been heavy in southern counties in Missouri in fescue, Bermuda, and alfalfa," said Scheidt.

The threshold level is four per square foot.

"If heavy defoliation is seen, but no larvae, check the closest field in a lush area, as larvae may have already moved to the next pasture. Fields with lush growth are most at risk, as moths are attracted to lush fields," said Scheidt.

Source: Jill Scheidt, (417) 682-3579

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