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Forages & Grains
Volume 64 Number 17 Date 08/22/2019 POTATO LEAFHOPPER - Late August surveys in alfalfa found moderate to high counts of 0.2-2.7 leafhoppers per sweep, with an average of 1.7 per sweep. Pressure from this insect has been generally high this season, likely influenced by spring weather patterns that brought large migrations into the state. A few western Wisconsin fields sampled in July contained "hotspots" of 5-7 leafhoppers per sweep, the highest counts recorded in several years. PLANT BUG - Nymphs were less common in fields sampled this week, indicating population growth is slowing. Counts averaged 0.5 plant bugs per sweep and ranged from 0.1-1.6 per sweep. GRASSHOPPER - Late-season grasshopper activity has increased in alfalfa and other crops. 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 acceptable when the defoliation is concentrated at the field edges. PEA APHID - Populations of this forage pest are still low. Most fields sampled from August 15-21 contained fewer than 0.5 per sweep (50 per 100 sweeps). -- Krista Hamilton, DATCP Entomologist 
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