Forages & Grains
Volume 63 Number 16 Date 08/23/2018
POTATO LEAFHOPPER - Late August surveys in alfalfa found only low to moderate counts of 0.2-1.5 leafhoppers per sweep, with an average of 0.5 per sweep. Levels of this insect have generally been below threshold all summer long, despite a timely spring arrival and very favorable temperatures. Although a few individual fields sampled in late July contained localized "hotspots" of high leafhopper counts, none had a fieldwide average exceeding the two leafhopper-per-plant threshold for alfalfa growth 12 inches or taller.
PLANT BUG - Nymphs were less abundant in fields sampled this week, indicating population growth is slowing. Counts averaged 0.6 plant bugs per sweep and ranged from 0.1-1.8 per sweep.
GRASSHOPPER - Late-season grasshopper activity has increased in alfalfa and other crops in the abnormally dry central and northern counties. Grasshopper damage to forage crops can be serious at this time of year, especially in new alfalfa seedings and when dry weather slows plant regrowth after harvest. Insecticide use is justified if populations reach 20 grasshoppers per square yard at the margins or eight per square yard within an alfalfa field. Spot treatment is acceptable when the defoliation is concentrated at the field edges.
PEA APHID - Populations of this forage pest are still low. Most fields sampled from August 16-22 contained fewer than 0.5 per sweep (50 per 100 sweeps).
-- Krista Hamilton, DATCP Entomologist