What are Thrips and What is Their Life Cycle?

Thrips are tiny insect pests that can cause significant damage to a wide range of plants. There are thousands of different thrip species, and most are bad news if they end up in your greenhouse or garden.

The thrip life cycle consists of five stages: the egg, the larval, the prepupal, the pupal and the adult stages. Thrip control is usually best achieved using a combination of monitoring and preventative measures.

What are Thrips?

Thrips are tiny, skinny insects that feed on a wide variety of host plants. There are around 6000 known species of thrips, but most are tiny (less than 1/20 inch long) with long, narrow, fringed wings and puncturing, sucking mouthparts. Thrips come in a variety of colors and may be white, yellowish, dark brown, or black. Their feathery wings make them weak fliers, and they tend to get around by floating on the wind or stowing away in infested plants.

Thrips are serious plant pests, and cause extensive damage to their hosts. They feed by puncturing plant tissue and sucking out the contents of cells, which can cause silvering or speckling of the leaves.

Keep in mind!

Thrips tend to poop as they feed, leaving flecks of black, varnish-like substance (called frass) behind them.

There are many different species of thrips, and different species feed on different plants. They may be found on avocadoes, beans, blueberries, citrus plants, peppers, onions, strawberries, ornamental plants, and more.

What is the Life Cycle of Thrips?

The life cycle of thrips is completed in 5 stages. These are the egg, larval, prepupal, pupal and adult stages.

Eggs

Thrip eggs are elongated and cylindrical or kidney-shaped. Female thrips deposit their eggs on or into the flowers, leaves, buds, stems or fruit of the host plant. Some thrip species may lay up to 10 eggs per day for the duration of their lifespan.

Larvae

The larval stage of thrips consists of two instars that feed on the leaves, flowers and fruit of the host plant as they develop. During this stage, the thrip will molt twice before entering its prepupal phase.

Prepupae and pupae

The prepupae and pupae of thrips are non-feeding stages. The prepupal stage lasts around 1 day and the pupal stage typically lasts 2-3 days. Most thrip species drop off the plant when they reach this stage of their development and pupate on the soil or leaf litter, though some species pupate on the plant. During this stage, the thrips grow their wings and antennae.

Adult thrips

Adult thrips emerge from their pupae after approximately 2-3 days. The adults have wings but are weak fliers, and usually get around by floating on the wind. The time it takes for thrips to develop from eggs to adults varies depending on the species and the climate, but can take as little as 2 weeks.

Thrip damage

Thrips can cause significant damage to their host plants, and their feeding can cause stunted growth, damage and discoloration to leaves, leaf drop and discolored flowers and fruits. Some thrip species (like the Western flower thrip) are also known to transmit pathogens such as Impatiens necrotic spot virus and Tomato spotted wilt virus to plants.

Thrip control

If you spot thrips on your plants, you should take control measures immediately to prevent widespread damage.

Monitor your thrips

If you suspect you have thrips, the first thing you should do is set up some monitoring measures.

This will, firstly, confirm that thrips are the problem and, secondly, help you to keep tabs on their numbers.

Yellow sticky traps are an inexpensive and easy way to monitor plant pests – simply place them near your plants, and examine them later for thrips.

Use natural predators

Thrips have lots of natural enemies, including predatory thrips, green lacewings, minute pirate bugs, mites, and some species of parasitic wasps. These can be released into gardens and greenhouses to reduce thrip numbers. However, it’s important to identify your thrips properly first, as different thrip species have different natural enemies.

Keep weeds at bay

Thrips may move onto your garden or greenhouse plants from weeds. This often happens in spring and summer, when weedy areas begin to dry out and thrips go looking for more suitable, well-watered hosts. You can avoid this by keeping on top of weeds in your backyard, or by avoiding planting ornamentals, fruit plants and veggies in weedy areas, where they may be susceptible to thrip-attacks.

Cover your plants

Covers made of fine mesh can create a physical barrier that protects your plants from thrips and other pests. This method is usually implemented when plants are young and vulnerable to attack, and covers are often removed when the plants grow larger to allow growing space and to prevent overheating.

Use reflective mulch

Spreading reflective mulch under your plants can help to deter thrips, as well as other pests such as leafhoppers, aphids, and whitefly. Silver or gray mulch will reflect light, which interferes with the ability of flying pests to locate and land on plants.

Conclusion

Thrips are common garden and greenhouse pests. These tiny bugs use specialized mouthparts to pierce plant tissue and suck out the contents of cells, which can lead to stunted growth, damage and discoloration to leaves, leaf drop and discolored flowers and fruits.

The thrip life cycle takes approximately 2 weeks completes, and consists of an egg stage, a feeding larval stage, non-feeding prepupal and pupal stages and, finally, an adult stage. Thrips can be monitored using yellow sticky paper and controlled with the help of natural predators, proper weed management, plant covers and reflective mulch.

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