Thursday, July 11, 2013

Southwest Missouri Field Crop Report for July 10

Contact: Jill Scheidt, agronomy specialist
Tel: (417) 682-3579 

LAMAR, Mo. –Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County, scouted area fields on July 10 to prepare this week’s field scouting report.


Japanese beetle and grasshopper feeding was seen in area corn and soybean.  Threshold levels for defoliation in corn and soybeans are 20 percent defoliation before bloom/pollination and 30 percent defoliation during or after bloom/pollination.

During pollination, only while the silk is green, threshold for Japanese beetle in corn is when three plus beetles are clipping silks to less than one-half inch.  A high rate of 10.3 oz/acre Hero is recommended to control Japanese beetles. 

“Be sure to walk far into the field to determine threshold levels.  Japanese beetles often feed only on the edges of fields and therefore do not require treatment,” said Scheidt. “It is also difficult to control Japanese beetle because they come in flights so insecticide residual usually only controls the first flight and not the following flights.”


Holcus spot was seen in corn fields also.  Holcus spot is identified by round to elliptical spots, ranging from 2-10 mm in diameter.  Lesions first appear water soaked and later become white to tan and eventually turn dry and brown. 

“Holcus spot can often be mistaken for herbicide damage,” said Scheidt. Holcus spot usually is not severe; crop rotation and tillage are the recommended control, although not very effective because of the broad host range of holcus spot.


According to Scheidt, there are two methods to estimate soybean population.  Measuring off 10 feet in one row and dividing by certain numbers according to row spacing, or using a hula hoop.

Go to at least three areas in each field and count population estimates in three spots within the three different areas to get the best population estimate.


The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension. For more information on this scouting report, or to learn how to receive it a week earlier by telephone, contact the MU Extension Center in Barton County, (417) 682-3579.

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