Alfalfa can tolerate fairly high pea aphid populations. The simplest and most accurate method of taking actual counts of pea aphids is to estimate numbers per stem. This is somewhat similar to stem sampling for monitoring tip injury due to alfalfa weevil. The stems must be very carefully cut and handled since pea aphids readily fall from the plant when disturbed. Of the three, the Tarnished and Alfalfa Plant Bugs are the more consistent pests.
Populations are usually highest on the second and third regrowth cycles.
Back to Table of Contents Seasonal Schedule for Insect Scouting in Alfalfa Spring Growth Estimate percentage of terminals injured by alfalfa weevil and check for live larvae. Observe if unusual numbers of spittlebug nymphs, plant bugs, grasshoppers, cutworms or other occasional pests are present. Second and Third Growth Check stubble to see if alfalfa weevil larvae are feeding on and retarding growth. Sweep net sample for potato leafhopper. Stem sample for pea aphid 2 weeks prior to harvest if large numbers are detected in sweep net samples.