Forages & Grains
Volume 52 Number 8 Date 06/15/2017
ALFALFA WEEVIL - The peak larval damage period is expected to end by late June as populations transition into non-feeding pupal stage. Larvae are still common in low to moderate numbers in second-crop alfalfa. The average count from June 8-14 was below 0.3 per sweep and leaf tip feeding was less than 30% in most surveyed fields.
PEA APHID - Levels of this insect have been decreasing since early June. Densities currently range from 0.1-3.8 per sweep and average less than one per sweep. The rainy, humid weather of the past week favors the spread of fungal pathogens that may contribute to aphid population decline.
POTATO LEAFHOPPER - Counts are escalating in second-growth alfalfa and in vegetable crops. Numbers in 8-16 inch regrowth in the southern and western districts ranged from 0.1-1.5 adult leafhoppers per sweep this week and averaged 0.5 per sweep, whereas average counts were less than 0.3 per sweep in all fields sampled during the previous week. A few 12-inch fields in the Arcadia area of Trempealeau County had above-threshold populations of 1.1-1.4 per sweep. Development and reproduction are expected to increase by late June and the economic threshold of 1.0 per sweep in 6-12 inch alfalfa and 2.0 per sweep in alfalfa taller than 12 inches could be exceeded in more fields. Continued sampling of alfalfa regrowth is recommended.
MEADOW SPITTLEBUG - The adult stage of this insect is collecting in alfalfa sweep net samples, signaling that the population has matured and their distinctive frothy spittle masses will not reappear until next spring.
-- Krista Hamilton, DATCP Entomologist