Orius tristicolor  and O. insidiosus
Hemiptera: Anthocoridae

Minute Pirate Bug and Insidious Flower Bug

Orius  spp. are "true" bugs and occasionally may bite humans, but the bite is only temporarily irritating.

Appearance

Adults are very small (3 mm long), somewhat oval-shaped, and black with white wing patches. Wings extend beyond the the tip of the body. Nymphs are small, wingless insects, yellow-orange to brown in color, teardrop-shaped and fast moving. Both adults and nymphs feed by sucking juices from their prey through a sharp, needle-like beak (the rostrum), which is characteristic of all true bugs.

Habitat

Orius is common on many agricultural crops including cotton, peanuts, alfalfa, corn, pea, and strawberry, on pasture land, in orchards, and is successfully used as a biological control agent in greenhouses. It is often found in corn silks and is most common where there are spring and summer flowering shrubs and weeds since it feeds on pollen and plant juices when prey are not available. In the Midwest, O. insidiosus is more common, while O. tristicolor is more common in the western states. In greenhouses, Orius spp. are used as generalist predators, especially on cucumber and bellpepper crops.

Pests attacked

Both immature stages (nymphs) and adults feed on a variety of small prey including thrips, spider mites, insect eggs, aphids, and small caterpillars. Orius holds its prey with its front legs and inserts its beak into the host body, generally several times, until the soft body is empty and only the exoskeleton remains. It has been reported to be an important predator of the eggs and new larvae of the bollworm and of spotted tobacco aphid, but it is believed that thrips and mites are the more basic part of an Orius diet. It can also be an important predator of corn earworm eggs which are laid on the silks. Other reported prey include eggs and small European corn borers, corn leaf aphids, potato aphids, and potato leafhopper nymphs.

Life cycle

Females lay tiny eggs 2-3 days after mating within plant tissues where they are not easily seen. These hatch into nymphs which develop through five nymphal stages. Egg incubation is generally 3-5 days, and development from egg to adult takes a minimum of 20 days under optimum conditions. Females lay an average of 129 eggs during their life spans, and adults live about 35 days. Several generations may occur during a growing season.

Relative Effectiveness

Both immature and adult bugs can consume 30 or more spider mites per day, although Orius has been observed to leave prey before having completely consumed it to attack another mite. Nevertheless, the first mite was incapacitated and so more mites may be destroyed than those needed to fulfill nutritional requirements.

Conservation

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 Orius. Plantings of spring and summer flowering plants will help them survive periods of scarce prey.

For general information about conservation of natural enemies, see Conservation in the Tutorial section on this site, or the Volume II, No. 1 Feature Article on conservation in the Midwest Biological Control News Online.

Pesticide susceptibility

Foliar applications of insecticides to crops can greatly reduce Orius numbers. Even soil-applied systemic insecticides may reduce their numbers because of their habit of sucking plant juices.

Commercial availability

Orius are available commercially from insectaries (see the off-site publication, Suppliers of Beneficial Organisms in North America), 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.

Taken from:

Wright, Bob (1994) Know Your Friends: Minute Pirate Bugs, Midwest Biological Control News Online. Vol.I, No.1.

Additional References

Askari, A. and Stern, V.M. 1972 Biology and feeding habits of Orius tristicolor (Hemiptera: Anthocoridae), Ann. Ent. Soc. of America., 65: 1, 96-100.

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