Forest Pests: Insects, Diseases & Other Damage Agents

Pine thrip (Taeniothrips pini Uzel)

From: Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests
(Atlas skodliwych owadów lesnych) - Multico Warszawa, 705 pages. Original publication in Polish. English translation provided by Dr. Lidia Sukovata and others under agreement with The Polish Forest Research Institute.

Occurrence: T. pini occurs in the northern, central and eastern Europe and the United Kingdom. Usually it is observed in lowlands. In Poland T. pini is a very common species and the caused damage is often considered to be due to other insect pests.

Host Plants: T. pini occurs and causes damage mainly in young, up to 40 years old larch stands located nearby spruces. A spruce that the insect is often observed on during autumn and winter is not its host tree but serves as an overwintering place.

Morphology: T. pini is a very small insect. Its body is very elongated. Female adults are grayish-brown, 1.2 mm long, while male adults are orange-yellow, 0.8 mm long. They have 6-segmented antennae and two pairs of very narrow wings. The underwings are transparent. The edges of both pairs of wings are densely covered with long setae. The egg is been-shaped, 0.3 mm long, transparent just after being laid, and becomes yellow, non-transparent later on. Newly hatched larvae are white, older larvae are yellow or orange. They grow up to 1 mm in length.

Biology: Mated females overwinter. Eggs are laid from late May through June on needles of developing young larch shoots. Larvae of the first generation hatch 2 weeks after being laid. They suck a sap on needles and young shoots. Larvae molt twice. Adults of the second generation emerge in July or August. They move on to the spruce. Female adults of the second generation overwinter in terminal buds of the spruce. Next spring they move back to the larch.

Damage: Adults and larvae of T. pini suck on young larch needles and shoots. Damaged needles become grayish, curve and fell down. Small resin outflows are observed on a bark of shoots. Heavily attacked shoots curve and die. It causes some loss in height increment. Larch trees heavily attacked by T. pini start dying from the top.

Preventive measures: Light availability and a luck of spruce trees around are important conditions required to prevent infestation of larch trees by T. pini.

Control measures: If there are more than 100 specimens of T. pini per 10 cm of the end part of a shoot, the treatment with a systemic insecticide is suggested.

Diagram, Multiple life stages and damage. Poland Image by Robert Dzwonkowski

Damage, To larch shoot Image by Stanislaw Kinelski

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