Latin name: Frankliniella spp.
Reason for Concern:
1) Rarely a problem, thrips are tiny insects that can infest blooms and berries.
2) They can be a problem in specialty packs (e.g., kosher).
3) Common flower feeders; when abundant, have been reported to cause blossom blasting.
4) Feed on fruit and contaminate harvested fruit. A toxin in their saliva can distort, discolor or destruct plant tissue.
Tiny (1mm long, less than 1/20”, at maturity), slender insects with long fringes on the margins of both pairs of their long, narrow wings. Nymphs are similarly shaped but lack wings. Color ranges from reddish yellow to dark brown. Larvae are about 0.25 mm long, white or cream-colored during the 1st instar, turning more straw-colored during later stages.
Adults and larvae are slow-moving and have long, stout abdominal hairs visible with a hand lens. Thrips feed by puncturing a host plant and sucking exuding contents, which causes tiny scars on leaves and fruit (stippling), and can stunt growth. Damaged leaves may become papery and distorted. Infested terminals may discolor, roll, and drop leaves prematurely. Damage is often observed before thrips can be seen. Discolored or distorted plant tissue or black specks of feces around stippled leaf surfaces are clues of thrip presence. Other disorders, pathogens, and invertebrates can cause damage resembling that of thrips. Lace bugs, plant bugs, and mites also stipple foliage, and lace bugs and certain plant bugs produce dark, watery fecal specks.
Life cycle may be completed in 2 weeks in warm weather with up to 8 or more generations a year. The adult lays elongated, cylindrical to kidney shaped eggs that are relatively large in relation to the female in leaves or buds. Nymphs hatch and enter 2 or more instars before entering the prepupal and pupal stage. The pale prepupae and pupae of most species drop to the soil or leaf litter or lodge within plant crevices. The ‘pupae’ emerge as winged adults and migrate back to the plants or out of the field.
- Thrips feed on flower pollen and are usually hidden within plant parts (such as buds), making them difficult to detect and control with insecticides.
- When berries develop, look for discolored drupelets.
- Keep an eye out for beneficial thrips as well as pest thrips.
- The six spotted thrip is a beneficial insect predator. It has three dark spots on each forewing, unusually long hairs extending well beyond the margins of the head and thorax.
- In comparison, pest thrips may have wings with broad alternating dark and light bands, but no three distinct dark spots; hairs on the head and thorax are shorter.