Thrips are among the most common and frustrating plant pests affecting gardens, greenhouses, and indoor plants worldwide. These tiny insects cause significant damage to a wide variety of ornamental and edible plants through their rasping-sucking feeding behavior that scarifies plant tissues and spreads plant viruses.
Despite their small size making them difficult to see with the naked eye, thrips create distinctive damage patterns that alert gardeners to their presence. Understanding thrips identification, lifecycle patterns, and management strategies helps protect plants from these persistent pests that can rapidly build populations and devastate crops when conditions favor their reproduction and development.
What are thrips?
Thrips are tiny slender insects belonging to the order Thysanoptera, with over 6,000 species worldwide and several hundred species found in North America. These minute pests measure 1/25 to 1/8 inch in length, making them barely visible to the unaided eye. Most thrips are plant feeders that damage leaves, flowers, and fruits through their unique feeding method involving rasping plant surfaces and sucking up released cell contents.
Common pest species include western flower thrips, onion thrips, greenhouse thrips, and various other species affecting specific crops or plant groups. Thrips infest both indoor and outdoor plants, causing problems in greenhouses, homes, gardens, and agricultural fields throughout growing seasons.
Beyond direct feeding damage, many thrips species transmit serious plant viruses including tomato spotted wilt virus and impatiens necrotic spot virus that can devastate susceptible crops. Their role as virus vectors often causes more economic damage than their feeding injuries alone.
Thrips are found on virtually all plant types including ornamental flowers, vegetables, fruits, and greenhouse crops. Their tiny size allows them to hide in flower buds, between leaves, and in other protected plant parts where they’re difficult to detect until damage becomes apparent. Some thrips species are beneficial predators feeding on mites and other tiny arthropods, though pest species far outnumber beneficial ones.
What do thrips look like?
Adult thrips have elongated, slender bodies with narrow profiles that allow them to squeeze into tight spaces within flowers and between leaves. Most species measure 1/25 to 1/8 inch long, appearing as tiny dark specks or slivers when observed on light-colored surfaces. Coloration varies by species from pale yellow or white to brown, gray, or black, with western flower thrips displaying yellowish-brown bodies while onion thrips appear darker brown to black.
Thrips have distinctive fringed wings featuring long hairs along the margins rather than the membranous wings of most insects. These feathery wings fold lengthwise along their backs when at rest. Despite having wings, thrips are weak fliers that rely more on wind currents for long-distance dispersal than active flight.
Their mouthparts are specialized asymmetrical structures used for rasping plant tissue rather than chewing or piercing-sucking like other insects. This unique feeding apparatus creates their characteristic damage patterns. Thrips have short antennae with 6-9 segments and compound eyes positioned on the sides of their heads.
Lifecycle of a thrip
Thrips undergo incomplete metamorphosis with egg, nymphal, and adult stages, though they have unique non-feeding pupal-like stages not typical of other insects with incomplete development. Female thrips insert eggs into plant tissues using their saw-like ovipositors, laying 40-300 eggs during their 30-45 day adult lifespan depending on species and temperature. Eggs hatch in 3-5 days under warm conditions, producing tiny first instar nymphs.
Nymphs pass through two active feeding stages (instars) over 7-14 days, resembling wingless adults as they feed on plant tissues. After the second instar, thrips enter prepupal and pupal stages lasting 3-7 days where they don’t feed and often drop to soil or leaf litter to complete development. Some species pupate on plants while others require soil contact.
Adults emerge from pupal stages and immediately begin feeding and reproducing. Many thrips species reproduce parthenogenetically (without mating), with unfertilized eggs producing all-female populations that reproduce even faster than sexually reproducing species. This reproductive strategy contributes to their pest status and difficulty of control once populations establish on susceptible plants.
Are thrips dangerous?
Thrips are not dangerous to humans as they don’t bite, sting, or transmit human diseases. Occasionally, thrips may land on people and cause minor skin irritation through their rasping mouthparts attempting to feed, creating temporary itching or pinprick sensations. These encounters are nuisance incidents rather than genuine health threats, and thrips cannot successfully feed on human skin or cause lasting harm.
However, thrips are extremely dangerous to plants, causing extensive damage through direct feeding and virus transmission. Their rasping-sucking feeding removes cell contents and creates silvery streaks, stippling, and distorted growth on leaves and flowers. Heavy infestations can cause complete leaf loss, stunted growth, and plant death in severe cases.
Do thrips kill plants?
Yes, thrips can kill plants through combined effects of direct feeding damage, virus transmission, and stress from sustained heavy infestations. Young seedlings, transplants, and small plants are particularly vulnerable to thrip damage that can cause death when populations overwhelm plants’ ability to produce new growth faster than thrips destroy existing tissues.
Flower crops suffer particularly severe damage as thrips feeding distorts blooms, causes premature flower drop, and renders flowers unmarketable even when damage doesn’t kill plants. Vegetable crops may survive thrip infestations but produce reduced yields, distorted fruits, or unmarketable produce requiring destruction despite plants remaining alive.
Cumulative stress from prolonged thrip feeding weakens plants and makes them susceptible to secondary problems including other pest infestations, disease infections, and environmental stresses that healthy plants would tolerate. This indirect mortality can be significant even when thrips feeding alone wouldn’t cause death.
Greenhouse and indoor plants face greater mortality risks than outdoor plants as enclosed environments allow thrip populations to build unchecked by natural predators and weather events that suppress outdoor populations. Without intervention, heavy thrip infestations in enclosed environments can indeed kill even mature plants through sustained feeding pressure.
Do thrips come back?
Yes, thrips frequently return after treatment due to their high reproductive rates, ability to reinfest from neighboring plants, and development of insecticide resistance in some populations. Thrips complete generations in as little as two weeks under optimal conditions, meaning surviving individuals can rebuild populations rapidly after control measures are implemented. Even small numbers of surviving thrips can produce damaging populations within weeks.
Thrips are excellent dispersers despite being weak fliers, using wind currents to travel between plants and properties. Outdoor plants can be reinfested continuously from neighboring gardens, wild plants, or agricultural areas hosting thrip populations. Indoor plants may be reinfested when new plants are introduced without proper quarantine or when thrips enter through windows and vents.
Some thrips species overwinter as adults in protected locations including leaf litter, plant debris, or greenhouse structures, emerging in spring to reinfest plants. This overwintering capability ensures seasonal populations return annually even after winter dormancy periods.
Prevention requires sustained monitoring and integrated management combining cultural practices, biological control, and judicious pesticide use rather than relying on single treatments. Ongoing vigilance is essential since thrips will persistently attempt to colonize susceptible plants whenever opportunities arise.
Where do thrips come from?
Thrips colonize plants from multiple sources making prevention challenging. Infested plant material represents the most common introduction pathway, with thrips hiding in flowers, leaves, and growing points of purchased plants from nurseries, garden centers, or other sources. Wind dispersal carries lightweight adult thrips from neighboring properties, agricultural fields, or wild plants, allowing colonization of previously clean plants.
Overwintering populations emerge from protected sites including plant debris, mulch, greenhouse structures, or soil where they survived cold periods as adults or pupae. Weed hosts surrounding gardens harbor thrips populations that migrate to cultivated plants as preferred hosts become available or when weed populations are disturbed.
Alternative hosts including ornamental trees, shrubs, and perennials may support thrip populations that periodically move to vegetable gardens and annual flowers. Many thrips species have broad host ranges, meaning numerous plant species can serve as population reservoirs.
Can thrips fly?
Yes, adult thrips can fly, though they’re weak fliers compared to most winged insects. Their distinctive fringed wings featuring long marginal hairs create surface area for flight but don’t provide strong propulsion or maneuverability. Thrips flights are typically brief, low to the ground, and cover short distances of a few feet at most through active flight.
However, thrips’ primary long-distance dispersal method involves wind currents rather than active flight. Their tiny size and light weight allow them to be carried passively on air currents for considerable distances, potentially traveling miles when caught in favorable winds. This passive wind dispersal explains how thrips rapidly colonize new areas and reinfest treated plants from distant sources.
Thrips fly more actively during warm, sunny weather when temperatures exceed 70°F. They’re attracted to light-colored surfaces, yellow and blue colors, and flowers, often flying short distances while searching for suitable host plants. Their weak flying ability makes them more visible on sticky traps than during actual flight since they struggle to escape once trapped.
How to know if you have a thrip infestation
Thrip infestations create distinctive damage patterns and signs visible before the tiny insects themselves are observed:
- Silvery stippling or streaking: You might notice characteristic silvery, bronze, or bleached streaks on leaves where thrip feeding has removed cell contents and created scarified tissue.
- Distorted new growth: It’s common to observe twisted, curled, or stunted new leaves and shoots indicating thrip feeding on tender developing tissues.
- Flower damage and discoloration: You might also find brown edges, streaking, or white flecking on flower petals, with blooms failing to open properly or dropping prematurely.
- Black fecal spots visible: You might also discover tiny black dots (thrip excrement) on leaf undersides and flowers accompanying feeding damage.
- Tiny moving specks observed: It’s common to see barely visible elongated insects on flowers and young leaves, especially when plants are shaken over white paper.
How to prevent a thrip infestation
Thrip prevention requires multiple integrated strategies addressing their various entry pathways and rapid reproduction:
- Inspect new plants thoroughly: Examine all purchased plants carefully for thrips before bringing them home, quarantining new additions for 1-2 weeks.
- Use yellow or blue sticky traps: Monitor for thrips presence using sticky cards that attract and capture adults before populations build.
- Remove infested plant material: Discard heavily infested plants immediately to prevent thrips from spreading to healthy specimens.
- Maintain plant health: Keep plants vigorous through proper watering, fertilization, and care, as stressed plants are more susceptible to thrip damage.
- Encourage natural predators: Preserve beneficial insects including minute pirate bugs, lacewings, and predatory mites that feed on thrips in outdoor gardens.
When to call a pro
When dealing with thrip populations damaging your plants and spreading plant viruses that are creating extensive plant losses and ornamental damage concerns, professional pest control services can provide effective thrip management and comprehensive treatment solutions. At Aptive, our pest control experts can assess thrip activity on your plants and develop targeted treatment programs addressing different life stages, which is crucial for achieving effective control of these rapid-reproducing pests and protecting valuable ornamental and edible plants.
If you’ve noticed thrip damage on your plants including silvery streaking, distorted growth, or flower damage, or have concerns about protecting valuable greenhouse, garden, or indoor plants from these destructive pests, don’t wait—contact Aptive today for a free quote. We’ll help you with effective thrip control while implementing integrated pest management strategies that protect your plants throughout the growing season.
FAQs about thrips
Here are some commonly-asked questions about thrips from homeowners worried about their plants.
Q: Can thrips jump?
No, thrips cannot jump. They move by crawling and flying but lack the specialized leg structures required for jumping like grasshoppers or fleas possess. When disturbed, thrips may suddenly take flight, which can appear jump-like to observers, but this is weak flying rather than true jumping. Their primary escape behavior involves dropping from plants or taking brief flights to nearby locations.
Q: Why do thrips keep landing on me?
Thrips land on people accidentally while being carried by wind currents or when attracted to light-colored clothing that resembles the pale flowers many thrips species prefer. They’re not specifically targeting humans but are weak fliers easily blown onto people during outdoor activities. Thrips may attempt to feed on human skin, causing minor irritation through their rasping mouthparts, though they cannot successfully feed on people. They’re particularly noticeable during mass emergence events when large populations disperse simultaneously. Wearing darker clothing and avoiding peak thrip activity periods during warm, windy days reduces encounters.
Q: Which plants repel thrips?
While no plants completely repel thrips, certain strongly aromatic herbs may provide some deterrent effects when interplanted with susceptible crops. Garlic, chives, basil, and marigolds are sometimes cited as thrip deterrents, though scientific evidence supporting their effectiveness is limited. More reliably, thrips show preferences for certain plants over others—they heavily attack roses, onions, and many flowers while rarely bothering ornamental grasses, most herbs, and some vegetables.
Q: Can thrips live in soil?
Yes, certain thrip life stages live in soil temporarily during their development. Many thrips species drop to soil or leaf litter to complete their prepupal and pupal stages, spending 3-7 days in the ground before emerging as adults. Some species overwinter in soil as adults or in pupal stages, surviving until favorable conditions return. However, thrips don’t live their entire lives in soil—they must return to plants to feed and reproduce. The soil-dwelling stages are non-feeding and vulnerable to soil treatments, making soil drenches effective control methods for some species. Well-draining soils may reduce survival rates.
Q: Where do thrips lay eggs?
Female thrips lay eggs inserted into plant tissues using their saw-like ovipositors, placing eggs inside leaves, stems, flowers, and fruits where they’re protected from desiccation and pesticide contact. Common egg-laying sites include leaf veins, flower buds, and tender new growth where tissue is soft enough to penetrate. Eggs are microscopic and completely hidden within plant tissues, making them invisible to the naked eye.
