David Owens, Extension Entomologist, owensd@udel.edu
Congratulations to Kathleen Heldreth for correctly answering last week’s guess the pest challenge. Green cloverworms are the most common worm encountered in vegetative stage soybean, and this year has not disappointed. They are a member of the ‘defoliator complex.’ Check fields for defoliation, fields with more than 35% defoliation canopy wide may warrant an insecticide application. Fortunately, most fields will not reach this level of defoliation and green cloverworms are pretty susceptible to most insecticides. There are a couple of other ‘green worms’ that show up in soybean. Right now, cabbage looper might be spotted in fields, but later in August we can expect soybean loopers. Both insects have 2 pairs of abdominal prolegs, instead of green cloverworm’s 3 pairs. Loopers also tend to have a larger, fatter last segment, and when prodded, do not move. Green cloverworms are like the insect equivalent of a walking hotdog, and they wiggle violently when disturbed, trying to get away from the myriad of predators that feed on them. Other green worms that may be found in a few fields in low numbers include various leaf tiers and bean leaf rollers. Both fold leaves over themselves. Leaf tiers tend to have a black head and a black ‘shield’ on the segment behind the head. Leafrollers have a large, dark head, orange spots, and a ‘neck’. Beet armyworms have a black spot above the 2nd pair of true legs and are often found in pigweed before other plants.
