How Long Can Thrips Live Without Plants?

Thrips are common greenhouse and indoor pests that can quickly damage plants But how long can they survive without access to live plant material? Here we’ll look at the details of the thrips life cycle and longevity to better understand how long they can persist in your grow room or home without plants

What Are Thrips?

Thrips are tiny, slender insects in the order Thysanoptera. There are more than 6,000 species of thrips in the world, and many of them eat plants. The western flower thrips (Frankliniella occidentalis) and the common blossom thrips (Frankliniella schultzei) are the two most common types that get into homes and greenhouses.

Adults are only 1 to 2 mm long and have wings that are narrow and fringed. Nymphs look similar but are smaller and wingless. Thrips use their rasping mouthparts to pierce plant cells, take nutrients out, and change the shape, color, and pattern of leaves, buds, and fruits. They can spread viruses as they feed and lay eggs.

Thrips Life Cycle

The thrips life cycle has six stages

• Egg – Females lay eggs on leaves and stems. Eggs are kidney-shaped and barely visible.
• Larvae – Wingless nymphs hatch and feed on plants. There are two larval instars.
• Prepupae – Mature larvae drop to the soil and construct cells.
• Pupae – Thrips undergo metamorphosis in the soil and emerge as winged adults after 5-15 days depending on temperature.
• Adult – Fully developed with wings to disperse and reproduce. Adults live 15-20 days.
• Overwintering – Some adults migrate to sheltered areas and enter diapause, remaining dormant until spring.

In warm places, the whole life cycle takes about three weeks. Thrips can produce 10-15 generations per year.

How Long Can Thrips Live Without Plants?

Thrips need living plants to provide food and breeding sites. However, some species can persist for extended periods without plants in certain circumstances:

• Adults – Up to 2-3 weeks. Adults can survive on reserves of fat and protein.
• Larvae – Around 5-7 days since they have fewer energy reserves.
• Pupae – Several months overwintering in plant debris or soil.
• Eggs – Potentially many months if laid in protected sites. Hatching triggers once temperatures warm.

Thrips adults and larvae die off quickly when they don’t have plants to eat, but the pupal and egg stages can live on. Cooler temperatures also prolong survival.

Overall, a thrips population cannot be sustained long-term without host plants. But pupae and eggs may persist for months in old pots, soil, or garden debris before emerging when new plants become available.

Factors Affecting Survival Without Plants

Several factors influence how long thrips can survive without plants:

• Species – Some thrips have greater fat reserves and cold tolerance. Onion thrips live longer than western flower thrips.
• Temperature – Cooler temps prolong survival. Thrips live weeks longer at 50°F vs 70°F.
• Humidity – Drier conditions cause faster water loss and death. High humidity extends survival.
• Life Stage – As seen above, certain stages like pupae persist far longer than adults or larvae.
• Food Reserves – Well-fed adults with ample fat reserves live longer than starved ones.
• Diapause – Thrips in dormancy require minimal resources to persist.

So cooler, humid environments help thrips conserve energy and moisture for longer lifespans when plants are absent.

Persistence of Thrips in Grow Rooms & Homes

In indoor spaces, most thrips stages die out completely within 1-2 weeks without plants. However, pupae in potting soil and eggs glued to surfaces may persist much longer.

For example, one study showed 8% of western flower thrips pupae survived for 35 days without plants at 68°F. Cooler temperatures would extend this further. Another study found up to 29% of eggs were viable after 30 days without plants.

So while adults, larvae, and most pupae die out quickly, a few may persist dormant in debris and emerge months later when plants become available again. Careful sanitation is key to preventing re-infestation.

Preventing Thrips From Re-Infesting Plants

To prevent thrips from re-emerging once plants are added back, follow these tips:

• Remove all plant matter and debris from the grow area.
• Wash down all surfaces with soap and water or disinfectants.
• Seal cracks, screens, and openings thrips could migrate through.
• Allow space to remain empty for 2-4 weeks to clear any remaining thrips.
• Quarantine and monitor new plants closely for signs of thrips.
• Apply preventative treatments like neem oil or insecticidal soap.

With diligent sanitation and preventatives, you can keep thrips from returning and damaging new plants placed into a cleaned grow space.

To summarize, most thrips life stages do not survive longer than 1-2 weeks without plants for food and reproduction. However, pupae and eggs may persist dormant for months in protected microclimates. Cool temperatures, high humidity, and overwintering diapause all enable thrips to live longer off of plants. Careful cleaning and preventative treatments are necessary to avoid re-infestations when adding plants back to a thrips-free grow room or home.

No, thrips are unlikely to go away on their own and often require intervention to control.