Whiteflies: a dangerous enemy of cannabis plants

The cannabis growers with some experience in the field have already learned the lesson: never let your guard down. You never know which terrible dangers are threatening your cannabis plants. One of the most common ones is, without a doubt, the whitefly. From the Aleyrodidae family, these tiny homopterous insects can throw a wrench in your crop before you even realize it.

Don't expect it to resemble a common housefly. This sap-sucking insect is about 1-1.5 mm long (males are even smaller) and has three pairs of legs and from two to four broad wings, depending on the species. There are over 1500 species of whitefly. The one generally attacking cannabis plants is called the greenhouse whitefly (Trialeurodes vaporariorum), a rather yellowish insect whose four wings are held flat over its body when resting.

Indoor weather conditions favor their reproductive performance, which is why they are most commonly found in indoor crops and greenhouses, where they become strong and spread rapidly. They love temperature ranges between 70 and 90 ºF, so make sure you always keep this parameter under control.

Another reason for their loving indoor environments is the absence of predators such as ladybugs or mites unless you expressly introduce them into your grow, of course. What's more, the dusty conditions of indoor environments trigger whitefly outbreak, and some of their best friends, the ants, which fight the insects that might naturally interfere with whiteflies, are found all over the grow.

How to identify whiteflies

However devastating, this plague is very easy to identify. Cannabis plants fear them so badly because they not only feed on their sap but they also transmit plant viruses they never seem to be able to fight due to their lack of strength as a result of their having had all their juices sucked up. For this very reason, remain watchful of any possible symptoms of infestation:

• If you believe the little holes or yellow, translucent dots that have recently appeared on the leaves could mean whiteflies have already settled, give your plants a good shake to see if they burst into flight.
• Also check the leaves for the presence of honeydew, a sticky substance that is excreted by the crawlers as they feed. The process is very simple: sap is rich in sugar but low in protein. So for whiteflies to get enough protein, they need to suck up virtually all the juices of the plant, secreting the excess of sugar in doing so. Honeydew can be really dangerous for plants for it can encourage the development of sooty mold, which can, in turn, hamper the photosynthesis.
• To top it off, ants are lured by this sweet liquid and provide protection to whiteflies fighting off their natural predators. This is down to the symbiotic relationship between both species: ants feed on the honeydew and whiteflies get protection.
• Another way to confirm the presence of these insects is to use a magnifying glass to look for the tiny eggs (0.25 mm tops) laid on the underside of leaves, which is where they stay during the larval stage.
• Once they've settled, it's very difficult to get rid of them because, during their 10-13 day long life cycle, they can reproduce in several occasions laying from 80 to 300 eggs in each clutch. They're almost unstoppable! To make matter worse, after some 6 days, the eggs hatch into translucent nymphs that are virtually invisible.

How to get rid of whiteflies

What makes this plague so scary is the speed at which it spreads. In just a month, the population of whiteflies can increase by 200%. This makes it essential to take action as soon as you detect the first symptoms, whether it's by using a biological or chemical product, except when your plant has already started the flowering stage for she won't have time to recover from such an aggressive attack.

• As for the organic insecticides that work best on whiteflies, you recommend treating your plants with a mix of neem oil and neutral soap. All you have to do is pour both of them into the same water-filled bucket and use the resulting solution to thoroughly clean the leaves. Make sure you treat them gently.
• Alternatively, strategically place sticky fly traps around your plants so whiteflies are attracted to them and end up trapped, unable to take off.
• Pyrethrin- or rotenone-based natural insecticides have also proved to be very effective. Try spraying the leaves with it and you'll see how quickly they disappear.
• You can also start a biological war against whiteflies, by introducing natural predatory insects to get rid of the eggs, the larvae, and the adults. Encarsia Formosa wasps, for example, can effectively stop this plague. Introduce two or more individuals every 2 weeks or so. Another devastating insect is Macrolophus Caliginosus, capable of eating whiteflies in all of their stages.
• By way of alternative, you can grow insect-repelling plants such as basil or marigolds around your cannabis plants.
• Chemicals do have immediate effects although they should be used only as a last resort. You must remember, though, that whitefly can become resistant to some of these products and that they have a stronger effect on larvae.

Prevention is always better than cure

To prevent any last-minute issues, it's highly advisable to take certain precautions before whiteflies even appear: the recommendations range from installing some powerful fans to stop them from landing on your plants to placing filters in every vent slot so the insects trying to access your grow room stay out.

Experts also like using Neem oil as a natural, cheap, and effective repellent. If you opt for it, you'll need to mix it with water and spray your plants every two weeks with the resulting solution.

Make sure your grow room is dust-free too. Keep it as clean as possible, especially after the trimming. And, of course, as pointed out earlier, it's important to keep temperatures down for whiteflies love hot environments. And no way in hell do we want to find them near us.