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Forages & Grains
Volume 65 Number 8 Date 06/18/2020 ALFALFA WEEVIL - The peak larval damage period will end by late June (800 degree days base 48°F) as populations reach the non-feeding pupal stage. Weevil pressure has been low this spring. The average count in 120 first-crop alfalfa fields sampled from May 22-June 17 was just 0.09 per sweep (9 per 100 sweeps) and leaf tip feeding was less than 35% in all surveyed fields. POTATO LEAFHOPPER - Recent alfalfa surveys found low averages varying from 0.02-0.3 per sweep, with the highest count (34 per 100 sweeps) observed in Iowa County. Nymphs, which can be an indicator of population increase, should begin appearing next week. MEADOW SPITTLEBUG - Adults have been collected in alfalfa sweep net samples, signaling that the population has matured. Meadow spittlebug damage is rare but occasionally occurs on first-year alfalfa seeded into small grain stubble. This insect has a single generation per year in Wisconsin. The risk of damage ends once the adults emerge. PEA APHID - This insect continues to be the most abundant alfalfa pest. Densities currently range from 2-11 per sweep and average three per sweep. After peaking in early to mid-June, pea aphid populations often collapse due to natural controls such as lady beetles, damsel bugs, parasitic wasps, and fungal pathogens. -- Krista Hamilton, DATCP Entomologist .jpg)
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