Field Guide     Pest Management     Soybean Looper

Soybean Looper

CROPS IMPACTED: soybeans, herbs, sweet potato, peanut, lettuce, cotton, tomato, tobacco

soybean-looper-1

Family: Noctuidae

soybean-looper-2 soybean-looper-3

About the Soybean Looper

Reproduction and Life Cycle

The soybean looper can have up to 4 generations per year. Eggs are laid individually by the adult loopers on plant leaves and will take about 3 days to hatch. The female can lay up to 700 eggs in their lifetime. The larvae will go through 6 instars in 2 to 3 weeks and then pupate on leaves undersides in a silken cocoon; this is also the stage of development that they will overwinter in. The generation developing in the middle of summer will remain in the pupal stage for 1 week. From egg to adult, it will take anywhere from 25 to 30 days. Soybean loopers tend to spike in population in August and September.

Soybean Looper Identification and Habitat

Identification

An adult soybean looper is a moth with brown spotted forewings that are 13 to 18mm long. Its entire wingspan is usually between 28 and 39mm. The eggs a female will lay are greenish-white, round, and are very small. The larvae are green and often have pale green or white stripes down their back with black dots. They have a small head and a thick body, especially at the rear and have 3 proleg sets. As larvae mature, they reach to be about 35mm in length. When the soybean looper is in its pupal stage, it takes on a cream-white or green-white colour with black spots and is about 16mm long.

Habitat

Soybean loopers are common in soybean fields and cultivated land. They can be found throughout the United States and pose a serious threat to crop yield if they are high in population. The larvae are the most damaging, often creating a high loss in foliage. After the larvae feed on a plant, they will leave it looking ragged in appearance. When a field reaches maturity, the plants are less likely to be damaged. That being said, during the development stage when soybean pods are filling, they are most vulnerable to injury.

Soybean Looper Management and Control Methods

Cultural Control

Due to the fact that this pest eats a number of different plants, make sure your fields are weed-free. There are also natural enemies to the soybean looper such as different parasite varieties. The parasite that attacks the egg is trichogramma pretiosum, the parasites that kill the larvae are hyposoter exiguae and copidosoma truncatellum, and also the parasitic fly called voria ruralis. The larvae will die when infected, usually spotted hanging from plant leaves as a dark sack of liquid. If these parasites are not present, then a chemical control management method would be advised when population is high.

Chemical Control

Insecticides you can use to help control the soybean looper if its population is above the economic threshold are bacillus thuringienis, indoxacarb, spinosad, and thiodicarb. It is important to note that this pest has become resistant to pyrethroid insecticides. Typically, as long as plants are not filling pods/blooming, plan to apply the insecticide when approximately 35% of foliage has been lost, or when soybean looper worms 13mm or longer are present with 8 or more per foot in a row. If plants are filling pods or blooming, then plan to apply the insecticide when at least 4 worms being 13mm in length or longer are present per foot or if there has been more than 20% of foliage loss. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy.

Latin / Alternative Soybean Looper Names

  • • Chrysodeixis includens

Sources

http://msucares.com/insects/soybeans/pubs/insect_management.pdf

http://ipm.ncsu.edu/AG271/soybeans/soybean_looper.html

http://bugguide.net/node/view/7595