Forages & Grains
Volume 63 Number 6 Date 06/07/2018
POTATO LEAFHOPPER - Surveys indicate that levels of this insect remain low in first-crop alfalfa. Counts in 50 fields checked from May 31-June 5 were less than 0.25 per sweep (25 per 100 sweeps). The economic threshold for leafhoppers in alfalfa taller than 12 inches is 2.0 per sweep. Second growth alfalfa is very susceptible to leafhopper injury and should be regularly sampled this month, especially if hot, dry weather continues.
PLANT BUG - Reproduction has increased and nymphs are common in sweep net collections. Combined counts of the tarnished and alfalfa plant bug species were below 0.8 per sweep in all fields surveyed this week.
ALFALFA WEEVIL - Larval counts are generally low for early June. The average this week was 0.1 per sweep (or 10 per 100 sweeps) in alfalfa sampled from Sauk County in the southwest to Portage County in the central area. Leaf tip feeding was below 20% in all surveyed fields, but harvesting the first cutting in the week ahead will be imperative for avoiding damage by the larger and more destructive third- and fourth-instar larvae. Scouting for weevils is recommended until new growth of the second crop is established.
MEADOW SPITTLEBUG - Nymphs are currently ½-¾ grown. The highest population encountered was seven per 100 stems in Sauk County, which is very low in comparison to the economic threshold of one nymph per stem. Most surveyed fields had few spittle masses.
-- Krista Hamilton, DATCP Entomologist