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Soybeans
Volume 63 Number 12 Date 07/19/2018


SOYBEAN APHID - Colonies on reproductive soybeans are low for mid-July. The average count in 31 fields sampled from July 12-18 was less than one aphid per plant. The highest average documented to date is only 25 aphids per plant in the Centerville area of Trempealeau County. Localized spots of 100-200 aphids per plant are not unusual within some fields, but field-wide averages are still extremely low, emphasizing the need for thorough scouting before control decisions are made. Insecticide treatment is not warranted until the threshold of 250 aphids per plant on 80% of the plants has been exceeded. Once again, aphid counts have not surpassed this level in any soybean field surveyed by DATCP this month.

JAPANESE BEETLE - This pest continues to cause light to moderate defoliation (5-10%) of soybeans along field margins. Infestations were noted in Columbia, Dane, Dodge, Fond du Lac, Jefferson, Sheboygan, Washington, and Winnebago counties this week. The economic threshold for Japanese beetle and other leaf feeding soybean pests decreases to 20% defoliation between bloom and pod fill. Limited spot treatment should be adequate to control beetles in fields where severe leaf feeding injury is confined to the perimeter areas.

GREEN CLOVERWORM - Low populations have been observed in southern Wisconsin soybeans since the first week of July. Defoliation attributed to this caterpillar and other leaf feeding pests has not surpassed the 20% threshold for reproductive soybeans. The last serious cloverworm outbreaks occurred in 2010.

-- Krista Hamilton, DATCP Entomologist