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Bug Series: How to Deal With Thrips

Thrips – a word that makes any houseplant collector shudder. These tiny bugs are primarily a problem indoors, where they are protected from predators and the elements, but they are common pests to vegetable and fruit garden as well. The bad news is, just a few thrips can do a lot of damage. The good news is, since damage is usually obvious when the population is still small, it’s easy to control them early.

Why They’re Good

Like every bug, thrips have their place in Mother Nature’s pecking order. Outside of providing food for many beneficial bugs, recent studies have found that several types of thrips actually carry pollen, making them itty bitty little pollinators.

When They’re Bad

Non-uniform patches of dead cells on the leaves, evidence that thrips have been feeding.

Thrips can cause a lot of plant damage, and an unhampered population can entirely destroy a plant over time. They also have a sweet tooth, snacking on berries, tomatoes, and other soft food crops. Since they are so tiny and can even burrow into a piece of fruit, they can make harvests inedible (who wants tiny white worms in their food?).

Thrips have a lot of natural predators and are susceptible to the elements, like most tiny insects. Because of this, major thrip damage or infestations are most common in houseplants or greenhouses, where they are left unchallenged by predators, wind, rain, and varying temperatures.

Where & When You’ll Find Them

Thrips thrive in warmer temperatures, and have a lifecycle of about 15 days. Outdoors, thrips emerge in early spring, and multiple generations will develop throughout the summer, hibernating when winter arrives. Indoors, thrips can thrive year-round.

Look closely and you’ll see thrip larva (tiny white strips) and adult thrips (larger black strips). This poor plant also has spider mites (evident by all the ‘dust’).

These bugs live on the plant for their entire lifecycle, and though they do develop small lacy wings, they can’t really fly. If

you’ve got them, you’ll find them on the leaves of your plants, or the fruit of your garden.

How They Impact Your Plants

Much like spider mites, thrips are sap suckers. They don’t actually eat the leaf or fruit tissue, but instead, suck out the sap and nutrients. This causes affected plant cells to die, and will cause stress, growth deformities, and ultimately death to a plant. Not to mention damaged harvests in your garden and edibles.

Identifying Thrip Damage

You’re likely to notice the damage left behind by these pests, before you notice them. Besides the fact that they are tiny and fast-moving, just a few thrips will leave noticeable damage.

An evident thrip infestation, with thrips at varying stages of their lifecycle.

As thrips suck the juices out of the plants tissue, they leave behind dead cells that appear as ‘silvery’ tissue in patchy, non-uniform and un-patterned groups on the leaves of a plant. Unlike spider mites, these guys actually start at the bottom of a plant and work their way up. That means you’re more likely to notice them near the bottom of the plant first. If you find a leaf with damage, but no thrips, look to the next leaf above it, and you’re likely to spot the culprit.

To the naked eye, thrips themselves look like tiny, white, cigar-shaped worms when they are in the larva stage. Once they become adults, they look more like tiny, long, slender black bugs. If you think you may have spotted one, but aren’t sure, blow gently towards the bug. If it’s a thrip, it will scurry away! You’ll find them camping on both the tops and bottoms of plant leaves.

How to Deal With Thrips

Thrips are small enough to move from plant to plant on a light breeze, or by

hitching a ride on a passing pet, human or housefly (yup!), so if you find an infected plant, be sure to separate it from your others while you address the issue.

A tiny thrip, tucked against the stem on the underside of this leaf.

Cut Off Suspicious Leaves: If your plant has enough healthy growth to manage it, of course. If you catch them early enough, you can quickly solve the problem by simply removing them from the plant.

Rinse & Wipe All the Leaves Down: If you can, spray your plant down with a hose, rinse it in the sink, and use your hand and a cloth to physically wipe the leaves clean of their unwanted guests.

Bacillus Thuringiensis: That mouthful of vowels is the name of a naturally-occuring, beneficial bacteria that kills many types of larvae, including thrips (also mosquitos and fungus gnats…). You can find this active ingredient in some organic gardening products, including Mosquito Dunks. This product is listed as a specific remedy for mosquito problems, but a lot of plant communities agree that, when added to your watering can, it’s useful tool for household thrip killin’.

Beneficial Nematodes: This is a great proactive remedy that can be used to combat a number of different insect pests – bonus points for the fact that it is completely organic and doesn’t harm other beneficial bugs (such as ladybugs and bees). Nematodes are microscopic worms that will feed on harmful larvae, deterring them from the surrounding environment. Nematodes are found in thousands of different varieties so you’ll want to get the specific type that feeds on thrip larvae. This remedy is most effective as a proactive measure (spray on your garden, plants and trees in the springtime, or add the nematodes to your soil). Pot Poppers for Gnat & Thrip control is super easy to use, and highly effective.

Pesticides: If you’ve got serious thrip infestation, then you may need to act a little faster. These guys are super tiny, so if you’re noticing adults with the naked eye, there are probably more larvae and eggs that you can’t see. Pesticides such as End All or Safers Insecticidal Soap will help destroy the thrip population quickly, but we recommend multiple applications to be sure you’ve dealt with all of them. Thoroughly coat the plant (top and bottom of leaves, as well as stems), and let it sit for about a week. Re-apply again in the same fashion to ensure that you get any stragglers, and after a few days of letting it dry, you can rinse the plant off gently with water to remove any leftover debris. We also recommend following this treatment with the application of Beneficial Nematodes or Bacillus Thuringiensis (both discussed above), which will proactively take care of any remaining eggs in the soil.

What About Other Bugs?

Check out our full bug series here, and follow us on Facebook to get notified as we release new articles in the series!

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Andrea Heembrock
Andrea works as Anything Grows Head of Marketing and Team Builder, and like everyone else at the store, she loves plants! Though she has many years of experience with plants, she gains a great deal of knowledge from her husband, Ty, who has been in the gardening industry for over two decades.

5 Responses

  1. This is a very informative post- I had thrips on one of my plants once so I just ended up composting it. Maybe next time I can actually save it if that ever happens again!

  2. Great info that indeed makes me shiver…
    The last couple of years have been noticeably bad for indoor plant pests.
    Additional question: if you use pesticide on a plant, would it kill the nematodes already in the soil?

    1. If you’re just using a insecticide spray on the foliage of the plant then you won’t kill any nematodes already in the soil, or any other beneficial soil creatures. Any pesticides applied directly to the soil will have some level of mortality rate on all the organisms living in there, including nematodes.

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