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Plant & Pest Advisory – June 18, 2025 – Michelle Infante-Casella
With higher temperatures increasing hatch times and spring grains like wheat and rye have drying
down, thrips may be more prevalent in vegetable crops, especially when small grains are adjacent to
vegetable fields. Thrips are very small and often missed if casually looking at a plant since they hide
in blossoms, under sepals, on under sides of leaves and other protected areas on the stems, leaves
and flowers. To scout for thrips, look at plant parts mentioned above. It is also important to dissect
a flower, pulling back petals and sepals to find hiding thrips. It is difficult to see thrips with the naked
eye. Therefore, the use of a hand lens will help.
Most adult thrips are elongate, slender, very small (less than 1/20 inch long), and have long fringes on
the margins of both pairs of their long, narrow wings. Immature thrips (called larvae or nymphs) are
oblong or slender and elongate and lack wings. Most thrips range in color from translucent white or
yellowish to dark brown or black.
Females of most plant-feeding species lay their elongate, cylindrical to kidney-shaped eggs on or
into leaves, buds, or other locations where larvae feed. Thrips have several generations (up to about
eight) a year. When the weather is warm, the life cycle from egg to adult may be completed in as
short a time as 2 weeks.
Thrips will feed on most all vegetable crops – solanaceous crops like eggplant, tomatoes, peppers,
white potatoes, cucurbit crops like cucumber, squash and melons, beans, allium like onions, garlic
and leeks and others.
Thrips feeding on plants can damage fruit, leaves, and shoots and very noticeably affect plants’
appearance. Leaves may be speckled on the top surface from feeding on under sides of leaves by
the insect’s sucking mouth parts. High populations often cause significant damage to leaves that may
at first glance mimic a foliar disease, but upon closer examination is thrips damage. Damage to fruit,
like tomatoes may not appear until fruit ripen and can be seen as gold flecks on red tomato fruit. For
many thrips species, by the time their damage is seen, such as after flowers open or fruit forms, the
thrips may no longer be present.
Once thrips are identified, control can be difficult when they are found in high numbers. Preventative
measures like the use of row covers and reflective mulch have some success. Both conventional
and organic insecticides labeled for thrips control can be found in the Rutgers Commercial Vegetable
Production Recommendations guide under the sections for individual vegetable crops. Always read
the pesticide label for instructions, safety precautions, application rates and restrictions. Since thrips
hide in tight areas of plant parts it is important to have good coverage and penetration when applying
insecticides to reduce the population of this hard to control pest.
For more detailed information about thrips see the Rutgers Fact Sheet
https://njaes.rutgers.edu/pubs/publication.php?pid=FS291