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Forages & Grains
Volume 58 Number 7 Date 06/13/2013 POTATO LEAFHOPPER - Surveys in the southern and central areas indicate that levels of this insect remain below established economic thresholds in both the first and second crops. Counts in 12- to 34-inch alfalfa in Dane, Green, Iowa, Monroe and Sauk counties ranged from 0.1-1.6 per sweep and averaged 0.5 per sweep. The economic threshold for leafhoppers in alfalfa taller than 12 inches is 2.0 per sweep. Second growth alfalfa is most susceptible to leafhopper feeding and should be closely monitored throughout June. Nymphs have not been observed as of June 12. ALFALFA WEEVIL - Larval counts and tip feeding have increased considerably in the southern and central counties where counts ranged from 0.3-10.4 per sweep and many unharvested fields are showing 50-90% defoliation. Much of the damage now occurring could have been prevented if rainy weather had not delayed harvest of the first alfalfa crop. Alfalfa fields must be cut during the next rain-free period and monitored for carryover of alfalfa weevil larvae. PLANT BUG - Adults and nymphs were found in low numbers of less than one per sweep again this week. Reproduction has accelerated and nymphs of both the tarnished and alfalfa plant bug are common in most field collections, although the tarnished plant bug is currently more numerous. MEADOW SPITTLEBUG - Spittle masses are increasing in size and most nymphs are currently ½-¾ grown. The highest population encountered was 13 per 50 stems near Sparta in Monroe County, which is low in comparison to the economic threshold of one nymph per stem. Most surveyed fields had significantly fewer spittlebugs. -- Krista Hamilton, DATCP Entomologist 
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