Pest Control: Thrips

There are many species of thrips, approximately 6,000 species have been described by entomologists. Thrips are worldwide pests with a wide range of host plants, the main ones being vegetable crops, field crops, flowers, fruit trees, citrus, and many ornamental plants. Some thrips are predators of other insects or mites, thus scouting and identification are crucial.

Two of the most common species of thrips are the Western Flower Thrip and the Tobacco Thrip

                                                                                            

The western Flower Thrips (Frankliniella occidentalis) is a worldwide pest with a wide range of host plants. A year-round invasive pest, they are less destructive during wet weather. The western flower thrips is a small insect with a narrow body (up to 1.2 mm in length) and yellowish in color. The male is smaller and lighter in color than the female; both have feathered wings and in the resting state they form a dark line along the back (where the wings meet).

Tobacco thrips (Frankliniella fusca) is a worldwide pest with a wide range of host plants. The tobacco thrips is a small insect with a narrow body; females are usually brown or black and the males are yellow, having eight segmented antennae. Some are winged (macropterous) and other aren’t (brachypterous).

Thrips can inflict various kinds of damage on a crop.

Direct damage

Adults and nymphs feed on plant sap reducing the chlorophyll content, thus causing yellowing of foliage, accompanied sometimes by dehydration and defoliation. If the infestation occurs early enough in the season, the death of young plants. Damage to the flowers appears as light spots on the petals, necrosis, blackening of the margins of the petals and discoloration of the flowers.

Indirect damage

The indirect damage is caused by the transfer of harmful viral diseases such as Tomato Spotted Wilt Virus (TSWV) and various disease vectors, such as Botrytis and Alternaria, which may penetrate via feeding sites. The typical signs of damage on fruit are silvering in sweet pepper, bronzing in strawberry, malformation in cucumber, and small perforations in tomato. In addition, there is a decrease in yield because of the falling of fruit.

Natural Enemies

There are specific natural enemies for different species of thrips.

The primary beneficial insects that are natural enemies of whiteflies are as follows: 

(Click the name of the beneficial insect for additional information) 

BioCucumeris - (Neoseiulus cucumeris) is a predatory mite widely used in the control of immature thrips (egg and larvae) as well as other species of mites. Although very small (1mm), BioCucumeris can be recognized by its oblong shape and quick mobility along the underside of leaves and in flowers.

BioStratiolaelaps - (Stratiolaelaps scimitus) is a soil-dwelling predatory mite whose nymphs and adults feed on fungus gnat larva, thrips pupae and other small invertebrates. These predatory mites stay at the base of plant stems and on the soil, rarely transferring onto the plant itself.

BioSwirski (Amblyseius swirskii) is an efficient predatory mite used for the control of young stages of the western flower thrips as well as the eggs and young nymphs of whiteflies. It also feeds on red spider mites as well as on broad mites.

BioAtheta - (Dalotia coriaria) is a fast-moving, soil dwelling rove beetle. A generalist predator, it feeds on a wide range of small insects and mites but is primarily an egg predator. BioAtheta is used in the control of fungus gnats, thrips pupae, shore flies, moth fly larvae, root mealybugs, springtails and other small arthropods.

BioOrius - (Orius laevigatus) is a predatory minute pirate bug equipped with piercing-sucking mouth parts, and two pairs of wings, the front pair being partially rigid. The adult is brown-black with grey spots.

BioSf - An entomopathogenic nematode containing infective juveniles of Steinernema feltiae in an inert carrier.

In addition to these insects, the following insects also target thrips along with their primary enemies:

BioAndersoni - (Amblyseius andersoni) is a predatory mite that feeds on small arthropod prey and pollen. BioAndersoni is less than 1mm in length and is often used in tomatoes due to its ability to maneuver between trichomes.

BioCalifornicus - (Neoseiulus californicus) is an effective predatory mite of a wide array of pest mites.