Thursday, September 27, 2012

Green Cloverworms and Fall Army Worms Steal the Show this Week in Area Soybean Fields

Fields north of Lamar were scouted on Wednesday, Sept. 19 by Wyatt Miller, an agronomy assistant with University of Missouri Extension in Barton County.

Soybeans scouted this week were between the R5, beginning seed stage, and R7, beginning maturity stage.

“Green cloverworms were seen this week at fairly high levels in one field,” said Miller.

Economic threshold for green cloverworms is met when defoliation reaches 20% or more during pod fill and 10 to 15 or more larvae are present per foot of row.

“Growth stage of soybeans should be taken into consideration before insecticide treatment is made. It is unlikely spraying for green cloverworms can be justified. Producers should also take into consideration preharvest restrictions, before applying pesticides to avoid delaying harvest,” said Miller.

Fall armyworms have been found in forage crops in counties southeast of Barton. Fall armyworms have been found feeding on alfalfa and cereal crops used for forage.

Producers should be scouting fields in the early morning for fall armyworms, especially in newly planted fields. If fall armyworms are active in a pasture or hayfield, it is suggested to graze or harvest as soon as possible to minimize the damage.

“Spraying this time of year can be difficult to justify because we are near the end of the growing season. However, depending on the value of the crop and growth stage, spraying may be appropriate,” said Miller.

Economic threshold for fall armyworm is four or more non-parasitized half grown or larger worms per square foot. The threshold is lower if the pest is attacking newly planted forages.


For more information on this scouting report or to learn how you can receive it by telephone each week, contact the MU Extension Center in Barton County at (417) 682-3579. These weekly field crop scouting reports are sponsored by MU Extension in Barton County.


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