How to identify and deal with thrips on marijuana plants
Last updated Published
Growing cannabis can be stressful enough without any unwelcome visitors. Fortunately, treating the tiny insect known as thrips is simple. Whether you are a novice or experienced grower, their arrival can be unnerving, and as such we have also collated some preventative measures you can take to stop them in their tracks.
Thrips are little insects that puncture into plants and sucking out the contentes. Depending on which stage in their life cycle thrips have reached they can be easily spotted by the naked eye. Fully matured they measure roughly 1-2 mm in length and although they may sound small and insignificant, left untreated thrips can cause serious problems, proving to be especially damaging during the early stages of your cannabis plants' growth.
The most common species to be found on cannabis is “Frankliniella Occidentalis”, commonly known as Tobbaco Thrips, and while solace can be taken in the fact that caught early enough the damage is not permanent, thrips attack a variety of plants, not just cannabis. To make matters worse, thrips can also fly, which makes it easy for them to move from one plant to the next, whether that be from marijuana plant to marijuana plant or a fruit or vegetable plant to your cannabis.
If you are considering growing cannabis indoors, then knowing what to look out for will make all the difference. Not least of all because thrips tend to favour indoor grows and greenhouses.
HOW DO THRIPS LOOK
Initial signs of a thrips infestation will be small silvery trails left across the leaves of your cannabis. Similar to the mark left behind by a snail, the markings will be accompanied by yellowing or browning of the edges of the leaves. Thrips damage the outer layer of the plant structure by rasping the leaf and sucking the sap out. Left untreated, leaves becoming deformed and will start dying.
If the thrips have reached their fully matured form, then you may also be able to spot them crawling about on the plant itself. Careful observation is required as they are naturally good at camouflage, but if they have reached the point where they are visible, then the chances of incurring losses are high.
You want to deal with them as quickly as possible. It is worth noting that eventhough scars on leaves seem small, they grow with the leaf to form stretchmarks which will occupy a larger area.
HOW TO GET RID OF THRIPS
Now for the fight back. The saving grace with thrips is rapid and prompt action can usually remove them. Organic bio-pesticides used every 2-3 days, or until you no longer see the telltale signs of thrips should remove any infestations. If you are experiencing a plague of biblical proportions, then chemical insecticides also work, but they come at the detriment of the environment and purity of any resulting buds. Chemical insecticides are the last resort and should be handled with extreme caution to make sure they do not taint the flowers.
Natural pyrethrins derived from Chrysantemum flower are one of the best contact killer for thrips. Usually they come in formulation with rapeseed oil or other ingredients. They kill the insects within minutes and leave little residue if used properly.
Neem oil or potassium soap are prime candidates, although, you should avoid spraying directly on buds hanging from matured plants. Just ensure that the rest of your plants receive plenty of coverage, and you continue the course of organic pesticide until you are confident the thrips have been dealt with. Stop spraying early in flowering, if you have to, spray only leaf surface and avoid the buds.
Another alternative for Thrips are Blue sticky traps, they attract Thrips better than yellow cards used for Fungus gnats and other flying insects. There are two approaches, they can be hung right above the canopy (about 30cm) or placed horizontally above the soil level in order to catch young insects leaving the soil.
PREVENTATIVE MEASURES ARE THE BEST APPROACH
Jumping back to our idyllic scene, there are many steps growers can take to prevent thrips from appearing in the first place. As is the case with most detrimental diseases, viruses or parasites, incorporating some preventive measures from the early stages of your grow make managing the cycle in its entirety significantly easier.
A good practice, regardless of potential thrip infestations, is to disinfect the entire growing area between cultivations. This includes any equipment used for trimming or planting. Also, ensure you refresh your substrate between crops to remove the risk of residual pupa or adolescent thrips.
Operating a clean growing environment and removing any weeds that start growing also help. Generally, giving the growing area daily love and attention will keep the majority of potential issues at bay.
Finally, using blue sticky traps can provide an early indication of any thrip appearance. And for the hardcore among growers, thrip nets can be placed over any intakes or outtakes for ventilation — an especially useful tool if you are growing in a greenhouse.
FEW LAST TIPS
- Its better to prevent than to cure.
- Avoid overfertilization with nitrogen. These insects love nitrogen overfed plants and thrive on them faster than when plants diet is balanced.
- Avoid overwatering the soil. Thrips reproduce partially in the soil, it is a well known fact that high water content facilitates soil insect reproduction.
- Scan your plants on a regular basis.