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Identifying Natural Enemies of Armyworms

On this page
  • Bigeyed bugs
  • Hyposoter exiguae wasp adult
  • Hyposoter exiguae larva
  • Minute pirate bugs
  • Polyhedrosis virus

Biological control agents such as predators and parasites may keep armyworm populations under control. Use the photos below to detect some of these natural enemies of armyworms. Names link to more information on identification and biology.

Click on photos to enlarge

Predaceous adult bigeyed bug
Bigeyed bugs
Identification tip: Adults and nymphs are oval, somewhat flattened, about 1/4 of an inch long, with a wide head and prominent bulging eyes.

Hyposoter exigua
Hyposoter exiguae wasp adult  
Identification tip: The adult wasp is black with lighter colored abdomen and legs, and 1/4 to 1/2 of an inch long. The adult wasp lays its egg in the caterpillar.

Although Hyposoter exiguae parasitizes both beet and yellowstriped armyworms, it is the most important parasite of beet armyworm.

Hyposoter larva
Hyposoter larva
Identification tip: After hatching, the larva develops within the caterpillar and the host caterpillar shrinks and becomes hard and brittle; if you pull apart a parasitized armyworm, a green larva will pop out.

Minute pirate bug attacking an aphid
Minute pirate bugs
Identification tip: Adults are small, 1/12 to 1/5 of an inch long, oval, black or purplish with white markings, and have a triangular head.

Polyhedrosis virus Polyhedrosis virus
Identification tip: The bodies of virally infected caterpillars turn into shapeless sacks of dark liquid and can often be spotted hanging from leaves. A nuclear polyhedrosis virus often reduces populations of beet armyworm in fall and winter.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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