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Forages & Grains
Volume 58 Number 5 Date 05/30/2013 ALFALFA WEEVIL - Larval populations are rapidly increasing in first growth alfalfa. Economic defoliation (>40%) and high counts of 200-650 larvae per 100 sweeps (2.0-6.5 per sweep) have been observed in southern Wisconsin fields since May 22. Damage is expected to intensify next week as larvae transition into the larger and most destructive third and fourth-instars, and alfalfa that is not harvested on time could be severely degraded. Control is justified when the economic threshold of 40% tip feeding is exceeded more than 7-10 days in advance of harvest. PEA APHID - Alfalfa fields sampled in the southern half of the state contained 1-144 aphids per 100 sweeps. The average count for the period of May 23-29 was 25 per 100 sweeps, a modest increase from nine per 100 sweeps the week before. MEADOW SPITTLEBUG - The first nymphs and spittle masses were observed in alfalfa late last week. Populations are currently below two per 100 stems. PLANT BUG - Representative counts are extremely low and range from 1-9 per 100 sweeps. Small nymphs of the tarnished and alfalfa plant bug species could appear by early June. -- Krista Hamilton, DATCP Entomologist 
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