Know Your Friends

Minute Pirate Bugs

Minute pirate bugs are common insect predators that are found in many agricultural crops, pasture land, and surrounding areas. Minute pirate bugs are "true bugs" (Hemiptera) in the family Anthocoridae. Both immature stages (nymphs) and adults feed on a variety of small prey, including spider mites, insect eggs, aphids, thrips, and small caterpillars. Both adults and nymphs feed by sucking juices from their prey through a sharp needle-like beak, which is characteristic of all true bugs.

Adults are very small (1/8" long), somewhat oval-shaped, and black with white wing patches. Females lay tiny eggs within plant tissues where they are not easily seen. These hatch into nymphs, the immature feeding stage. Nymphs are small, wingless insects, yellow-orange to brown in color, teardrop-shaped and fast moving. Growth from egg to adult takes a minimum of 20 days under optimum conditions. Several generations may occur during a growing season.

The most common species in the Midwest is Orius insidiosus, the insidious flower bug. Another species, Orius tristicolor, the minute pirate bug, is more common in western states. Both immature and adult Orius can consume 30 or more spider mites per day. They are often seen in corn silks, and can be an important predator of corn earworm eggs, which are laid on corn silks. Other reported prey include eggs and small European corn borers, corn leaf aphids, potato aphids, and potato leafhopper nymphs. Occasionally, Orius may even bite humans, but the bite is only temporarily irritating.

Minute pirate bugs are most common where there are spring and summer flowering shrubs and weeds, since they feed on pollen and plant juices when prey are not available. Foliar applications of insecticides to crops can greatly reduce their numbers. Even soil applied systemic insecticides may reduce their numbers because of their habit of sucking plant juices. Diversified cropping systems, use of microbial insecticides, e.g., products containing Bacillus thuringiensis, and use of economic thresholds to minimize insecticide applications, are all practical recommendations to maximize the natural biological control from minute pirate bugs.

Orius are available commercially from insectaries, but specific use recommendations have not been researched. They are shipped as adults in a carrier such as bran, rice hulls, or vermiculite, along with a food source. The carrier can be shaken onto plants, and the bugs will readily disperse and locate prey.

- Bob Wright, University of Nebraska - Lincoln

Drawing by Michele Schwengel. Photo courtesy of OSU Extension Service.
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