How do I control thrips?

Thrips are small, slender insects that can do a lot of damage to plants, both indoors and outdoors. These annoying pests spread at lightning speed and are often hard to get rid of. In this blog you will learn how to deal with thrips effectively, which species there are, and which control methods work best.

What are thrips?

Thrips are small, brown to black insects that grow to just 1 to 2 millimetres. They have fringed wings and live for between 10 and 30 days, depending on conditions and the time of year. In the Netherlands there can be as many as 7 to 12 generations of thrips a year, and they are active at temperatures between 12 and 30 degrees Celsius. Thrips lay huge numbers of eggs on plant material, which is part of why they spread so quickly.

Thrips species in the Netherlands

There are several species of thrips found in the Netherlands:

Western flower thrips: this is the most common species and also the most damaging. It turns up on all sorts of plants and crops.
Tobacco thrips: less of a problem for houseplants and often found in greenhouses.
Echinothrips: this species has been on the rise in recent years and is mainly found on ornamental crops. You can recognise it by its black colour with a white stripe across the leaf.
Japanese thrips: a fairly new species, first spotted in the Netherlands in 2014.

How thrips spread

Thrips can spread quickly because they lay large numbers of eggs and have a rapid life cycle. Although they are not strong fliers, they are often carried along by the wind, which lets them reach new areas easily.

Thrips larvae go through several stages before dropping to the ground to pupate. There they turn into adult insects, ready to damage the plant all over again.

The damage thrips do

Thrips cause damage by piercing the cells in leaves and sucking them empty for nutrients and sap. The affected cells turn silver or gold, and the thrips' droppings show up as tiny black dots on the underside of the leaves. It is not only the leaves that suffer: the growing tips are affected too. Damage to the growing tips can leave flowers misshapen and cause colour changes.

Controlling thrips

Controlling thrips can be a challenge, because they are persistent and very small. Chemical control is often ineffective because it does not reach the larvae in the soil or deep inside flowers. On top of that, adult thrips can easily lay fresh eggs after treatment.

Biological control is often the most effective method. It uses trap plants to catch large numbers of adult thrips, along with natural enemies such as predatory mites and parasitic wasps to bring the thrips population down naturally.

Chemical control is the easiest and most efficient way to get rid of thrips, though, especially if you want to see results quickly. The key is to step in early, before the infestation gets out of hand.

Tips for preventing thrips

Keep your plants healthy and make sure the air can circulate well.
Check regularly for signs of thrips.
Use trap plants to lure the adult insects in and catch them.
Consider bringing in natural enemies as part of your integrated control plan.

With the right approach you can keep the damage from thrips under control and stop them spreading any further. By taking preventive measures and combining biological with chemical control, you can keep an infestation in check and keep your plants healthy and thriving.