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Minute pirate bugs

Also known as Pirate bugs, Flower bugs, Orius, Insidious flower bug (Orius insidiosus), Anthocoridae

Beneficial or harmlessBeneficial
Adult minute pirate bug (Orius insidiosus) feeding on whitefly nymphs Photo: Orius_insidiosus_from_USDA_2.jpg: Photo by Jack Dykinga (uploaded by --gian_d 22:03, 15 March 2008 (UTC)) derivative work: Anna Frodesiak (talk) · Public domain

In short

Minute pirate bugs are tiny black-and-white predatory bugs that hunt thrips, spider mites, aphids, whitefly nymphs and insect eggs. Orius species are released in commercial greenhouses against thrips. They also feed on pollen, which helps them stay put when prey is scarce.

How it looks

Adults are about 2–5 mm, flat and oval, black with white-patterned wings (Orius), or mostly black, brown or purplish (Anthocoris), with bulging eyes and a piercing beak. Nymphs are wingless, oblong to pear-shaped, and yellow, orange, reddish or brown, developing wing pads as they grow. They are quick and are often seen in flowers, where thrips live.

Signs

Tiny dark bugs darting through flowers or over leaf undersides; thrips and mite numbers dropping.

Life cycle

Egg, five nymph stages and adult. Egg to adult takes about three weeks in warm weather, with several generations a year. In short-day conditions some Orius populations enter a reproductive rest.

What favours it

Flowering plants with pollen, and crops carrying thrips or mites. Broad-spectrum insecticides, ants and dust reduce them.

Prevention

  • Grow a few flowering plants that offer nectar and pollen near your collection, keep ants off infested plants, and avoid broad-spectrum, persistent insecticides.
  • Keep some pollen-producing flowers going near thrips-prone plants.

Treatment

Start with the first step and move down only if the problem persists.

  1. No control needed. In greenhouses, Orius can be bought and released against thrips, preferably early in the season; follow the supplier's instructions.
  2. If a spray is needed, choose a short-residual product, spot-treat and follow the product label.

Pros and cons

Pros

  • One Orius insidiosus can eat more than 20 western flower thrips a day, both larvae and adults.
  • Also takes spider mites, aphids, psyllids, small caterpillars, whiteflies and insect and mite eggs.
  • Survives on pollen and plant juices without harming plants.

Cons

  • They can pierce human skin; the bite is usually minor, from no reaction to mild swelling.
  • Less effective in short winter days in some regions because of reproductive rest.

Look-alikes

Thrips
Thrips are slimmer, cigar-shaped and yellow to brown or black with fringed wings; pirate bugs are oval and flat with a black-and-white pattern.
Plant bugs
Plant bugs (mirids) are larger, often green or brown, and feed on plants, causing spotting and distorted growth.

Where you find it

Flowering ornamentals, peppers, strawberries, greenhouse crops and other plants with thrips or mites.

Sources

  1. Minute pirate bugs — UC IPM Natural Enemies Gallery
  2. Anthocoridae — Wikipedia
  3. Ecology and Role of the Rove Beetle, Dalotia coriaria, and Insidious Flower Bug, Orius insidiosus, in Greenhouse Biological Control Programs — Scientific Research Publishing

Written in our own words from these sources. Check a product label before using any treatment.