Soybean looper (note color variation)
In Delaware, we have two species of loopers that occasionally cause economic damage to soybeans by feeding on soybean foliage, the soybean looper and the cabbage looper. Distinguishing between the species is difficult but soybean loopers typically have black true legs and black spots on their bodies (relying on this to distinguish between species is not always reliable). Soybean loopers do not overwinter in our area and moths migrate north on wind currents. Soybean looper larvae are tapered with an enlarged abdomen and have two pairs of fleshy abdominal pro-legs (do not count the pair of legs on the last abdominal segment). They move by rearing up on their fleshy pro-legs, arching their bodies and holding their heads up in the air. Sometimes they will be found resting in this position.
Soybean Looper
They can often be confused with green clover worms which have three pairs of abdominal pro-legs. Green clover worms will also wiggle violently when disturbed.
Green Clover Worm
Distinguishing between soybean loopers and green clover worms is important because soybean loopers are not effectively controlled with pyrethroids. The threshold for soybean loopers during soybean pod-fill stage is 15% defoliation.
Please refer to our Soybean Insect Management Recommendations for chemical control options: http://cdn.extension.udel.edu/wp-content/uploads/2012/05/18063934/Insect-Control-in-Soybeans-2017-final.pdf