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Forages & Grains
Volume 59 Number 16 Date 08/21/2014 POTATO LEAFHOPPER - Alfalfa surveyed in Buffalo, Jackson, La Crosse and Trempealeau counties contained 0.1-1.6 adults and nymphs per sweep. The average was 0.7 per sweep. Economic counts of 2.0 or more leafhoppers per sweep were not observed in the past week or at any time this season. PEA APHID - Populations of this forage pest are still extremely low. Most fields sampled from August 14-20 contained fewer than one per sweep. PLANT BUG - Nymphs continue to be abundant in sweep net collections, although average counts remain well below the five plant bugs per sweep threshold. Counts this week varied from 0.3-2.9 per sweep, with an average of 1.2 per sweep. GRASSHOPPER - Late-season grasshopper activity is increasing in alfalfa and other crops in the west-central and northwest areas. Moderate to severe defoliation in field margins and approximate counts of about 2-14 per square yard were observed at scattered sites. Grasshopper damage to forage crops can be serious at this time of year, especially in new alfalfa seedings and when dry weather slows plant regrowth after harvest. Insecticide use is justified if populations reach 20 grasshoppers per square yard at the margins or eight per square yard within an alfalfa field. Spot treatment is an acceptable form of control when the defoliation is concentrated at the field edges. -- Krista Hamilton, DATCP Entomologist 
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