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Thrips are a common threat to cannabis cultivators. They are small pests that look like little worms or flying insects. They are tough to get rid of and survive by sucking the sap out of your plants. Here is a quick guide to spotting thrips, and a few ideas for preventing and controlling an infestation.
You’ve got a plan in place to deal with aphids and slugs. Heck, you even actively shield your plants against the bad kinds of nematodes. But what’s your thrip strategy? Don’t leave your plants defenceless against these tissue-piercing critters. Once you get to the end of this article, you’ll have another notch on your pest management belt.
Contents:
Thrips are small flying insects that belong to the order Thysanoptera. Adult thrips are typically around 1.1 inches in length, feature two pairs of narrow wings, and range from white and yellow to brown and black in appearance. The life cycle of a thrip starts when a female adult lays eggs on leaves or bud tissue. Over the next two weeks, the hatched larva will transform into a pre-pupa, pupa, and finally an adult thrip. Because they multiply so quickly, thrip infestations can quickly get out of hand.
Much like aphids, another rampant cannabis pest, thrips also possess sharp mouthparts that allow them to puncture the leaves and stems of plants. Although they can’t pierce deep into plants, they still manage to penetrate surface-level cells and suck out all of the goodness within, including minerals and sugars. One or two thrips damaging a handful of cells pose little risk to healthy cannabis plants. However, large numbers of these pests can suck dry enough cells to stunt growth and reduce yields.
Thrips can absolutely fly. And don’t underestimate their aerial prowess based on their small size. These small critters can move over long distances by riding the wind. Even if thrips are present in a garden not directly adjacent to your own, they have the potential to access your weed plants regardless. Their ability to go airborne means growers need to consider how to protect their plants against their non-terrestrial movements. But worry not, you’ll discover some effective defense strategies below!
You’re now more clued up about these pesky critters, but how do you know when you have an infestation, and what does thrip damage look like? Of course, directly laying eyes on a thrip will confirm their presence. However, the key symptoms below will help you to detect them, even without seeing them yourself:
A small number of thrips is not a cause for concern. Although some growers might be tempted to reach for their pesticide of choice upon seeing a single specimen, you should only take such drastic action during a serious invasion.
Below, we’ll walk you through some of the best ways to eradicate thrips from your cannabis garden or growing room. After that, we'll dispense advice on preventing them from gaining a foothold to begin with.
We’ll mention chemical insecticides, but we don’t particularly endorse their use. These harsh and environmentally damaging compounds work to get large commercial operations out of sticky situations, but they have serious long-term consequences if relied upon. These chemicals temporarily paralyse insects and are often combined with piperonyl butoxide to ensure the eradication of the species in question. Because they break down rapidly, growers need to make sure they make immediate, direct contact with pests. Though effective, pyrethrins (pest-toxic chemicals found in chrysanthemum flowers) are known to cause harm[1] to aquatic life, beneficial insects, and honey bees.
This natural insecticide contains several active components that can stop thrips in their tracks, including azadirachtin[2]. As well as repelling insects, the compound prevents an array of insects from feeding, and disrupts their reproductive cycle. It puts an end to immediate damage caused by thrips and lowers their populations over time. To use it, simply add 1 tablespoon to 4l of water and add a few drops of dish soap to the mix. Stir thoroughly and pour into a spray bottle. Put on some gloves and eye protection, and get to work!
Thrips play an important role in several ecosystems and therefore have multiple natural predators. Cannabis growers can artificially introduce these beneficial species into their cultivation space to help bring down thrip numbers and control populations going forward. Some of the most effective predator insects for controlling thrips include:
Bacillus thuringiensis, more simply known as BT, is a species of bacteria that can help growers deal with a thrip infestation organically. After spraying BT on plants, thrips and other pest insects see them as a food source and quickly devour them. However, once consumed, they start to release insecticidal compounds. These toxins wreak havoc on the digestive system of thrips and swiftly kill them.
The options above are effective ways to deal with thrip infestations. However, you’ll save yourself time and effort, and protect your plants against stress and damage, by preventing thrips from becoming a problem in the first place. Now that you know the best thrip treatments, learn the most effective preventative measures.
Sticky traps are extremely simple but highly effective. Their bright yellow color naturally attracts thrips. Once they make physical contact with these sticky sheets, they become bound up and are no longer a threat to your plants. Simply hang several sticky traps around your plant canopies, and lay a couple on the surface of the soil to deal with pupae. While effective, sticky traps work in a scattershot fashion. They’ll also trap and kill other insect species, including beneficial ones. Keep this in mind when deploying this pest control method.
Netting also provides an extremely simple solution to thrip infestations. Netting with a narrow meshwork will help to keep an array of unwanted critters off your cannabis plants. Plus, if you enjoy growing food alongside your weed, this piece of kit will also help to protect Brassica plants against the dreaded cabbage white butterfly. Adding to this, you’ll also keep your plants safe from hungry birds and curious household pets.
Remember when we said a small amount of thrips isn’t anything to fret about? That’s because they naturally show up as members of several ecosystems. If you’re growing weed in a biodiverse garden, the predator-prey balance will equalise things and keep thrip populations at a natural level. However, many growers opt for monocrops over polycultures. While it seems like a more efficient way of growing at first, it often backfires and promotes the spread of pests and disease. Surround your weed plants with a rich diversity of herbs and flowers to attract beneficial insects and save yourself a lot of work when it comes to pest management.
Consider what could act as a vector for thrips to enter your garden or growing room. Your clothes, the bottom of your shoes, cuttings, and other forms of plant material can all introduce this pest to your cultivation space. Make sure to clean your boots and even change clothes after arriving home from your friend's garden. Maintain a zero-clone policy and produce your own cuttings to drastically slash the odds of pests and diseases working their way into your growing operation.
If you’re cultivating indoors, it’s a good idea to swap out your growing medium after each cycle. While more expensive than amending, it’ll help to keep pest problems down by removing eggs from the growing space between each run.
Thrips can cause real issues when growing cannabis. They pale in comparison to other pests and diseases in terms of severity, but they can still stunt growth and lessen yields. However, these critters are easy to detect and simple to deal with once discovered. Plus, you’re now equipped with the knowledge to prevent them from causing trouble in the first place. Go on and grow with confidence!