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Thripping Heck – Hydro Harvest Pest Control

Thrips may sound old fashioned, like something you’d catch down a coal mine perhaps, or a life-threatening Victorian snack. But far from being yesterday’s news these nasty, plant-bothering pests are lively, resilient, and can easily reap damage on an indoor crop.

Combining the worst qualities of Spidermites and Aphids whilst introducing a few little tricks of their own, Thrips complete the unholy trinity of plant-dwelling insects.

Happily, humans have been fighting Thrips for hundreds of years and have come up with a long list of effective techniques for dealing with the little blighters. As many of the remedies are natural they can be used without adverse effects on plant, crop, human, or beneficial insect health.

The Pest:

Thrips / Thunder Flies

Distinguishing Features:

Six legged, cigar-shaped and 1-1.5mm in length. Two pairs of thin hairy wings held tight to the body. Bumbling / bouncing in flight. Antennae on head.


Dark yellow / brown, black in places.

What they do:

Thrips are after your plant sap and will generally chow down on the leaves and young shoots to extract it. If they are present you can expect to see silvery marks that develop into white mottling on the upper surfaces of the leaves. These are Thrip bites.

Photosynthesis and leaf health are both negatively affected by Thrips feeding, if left untreated this can cause leaf death. With young plants in particular it can be a danger to the plant itself.

Damaging as this is, it’s not the only problem Thrips cause. The insects lay their eggs into the leaves which does further harm to the plant. When the eggs hatch out they leave yet more holes in the leaves, allowing bacteria to get in.

Not content with Swiss-cheesing your crops, the Thrips can carry viruses such as Tobacco Mosaic that a) attack the plant, and b) distract growers from the presence of Thrips.

Finally you should be aware that Thrips do not need a plant to live on. They are quite content to hang out on hard surfaces, carpets, clothes, grow tents, the list goes on. So dealing with the plant is not the last word in Thrip control.


Thrips are so randy they don’t even need another half to reproduce. Bring able to multiply without a mate means their population can expand quickly so a rapid response is key.

Firstly, confirm their identify using sticky traps and a magnifying glass. It is also possible to find Thrips on the plants themselves – look to lower regions and in areas affected by bite marks.

As with other pests it’s important to get their numbers in check. Predators and sticky traps can help with this, as can a wash down with Neem oil. Badly affected leaves should simply be pruned off and safely disposed of – don’t leave them lying around or anywhere near your plants.


Denying Thrips the opportunity to feed is an essential step in halting their progress. Products such as Plant Chemist Insect Control help you to do this by giving your plant a tough, yet non growth restricting membrane that stops Thrips dead in their tracks.

The insects are trapped on the surface of the plant and prevented from digging in. Stranded and starved the affected Thrips should simply die off.


If you want to attack the Thrips internally there are two ways to go. A.R.T.S Velgro uses potassium salt and Ryania to sterilise the insects, stopping them from reproducing.

On the other hand Guard Aid Thrip Control hits the respiratory and nervous systems of the insects hard, incapacitating and killing them in egg, larval, or adult form. Pyrethrum, its main ingredient, comes from the dried heads of chrysanthemum and has been used for centuries as a non-toxic insecticide.

These are great options as both are completely safe to use on all types of fruiting and flowering plants with no negative impact on taste, smell, or food safety.

Killermite will really do a number on Thrips too but it is more of a high impact insecticide, designed for decisive action.


When entering the grow room always dress for the occasion. That means fresh coveralls and grow room overshoes. It’s not a bad idea to change the clothes underneath too, especially if you’ve been around nature. This should help prevent Thrips from riding along on you.

Usual rules of quarantine apply to young plants. Really it’s best to avoid bringing in any organic matter in that you’re not 100% sure is clean. If you must do it then keep the new arrivals well away from your ‘live’ spaces.

Bug blockers and room seals will help prevent Thrips waltzing in uninvited. The insects and their eggs can also hide in grow media so always buy sealed, reputable brands, and change yours out after each crop.

Have at your hard surfaces and grow room materials between cycles too. That could mean a smoke bomb for the room itself whilst you give your appliances and grow tent a thorough clean down elsewhere.

The good news is that none of this requires great expense or hard manual work, certainly not when you weigh it against the worth of a thriving, happy grow room.