Pest Guide: Mealybugs
Mealybugs are soft-bodied insects in the family Pseudococcidae. They’re common in warm climates, and as cannabis growers know, they like to feed on marijuana plants. They cause comparatively minimal damage early on in the infestation, so growers who know what they’re looking for should have no problem finding and eradicating them before they experience significant crop losses.
What Are Mealybugs?
Mealybugs are interesting insects. The females of the species exhibit what’s known as reduced morphology, meaning they don’t have wings and look more like nymphs than full-grown adult insects. Female mealybugs do have legs though, which they use to move around and find the crevices in marijuana plants. Once they find a promising spot, they hunker down and form a protective wax-like layer over themselves. This allows the females of the species to feed on the plant’s sap in peace.
Male mealybugs’ sole purpose is to find females of the species and reproduce. They don’t even feed as adults, so growers don’t have to worry about the male mealybugs, themselves, but the fact that they have wings and fly around constantly looking for females makes them more noticeable, so keep an eye out.
Both male and female mealybugs are quite small. The females are slightly larger than the males, but they’re still no larger than a human fingernail.
Signs of a Mealybug Infestation
Have you noticed male mealybugs flying around? The females should be nearby. Check the stems and crevices of each plant to look for white, puffy clumps that look like cotton. That’s where the females can be found.
Mealybugs don’t have many natural defenses against predators, so they rely on ants for protection. If there are no ants, chances are, there are no mealybugs. Look at increases in the local ant population during the warmest months as an early warning sign that mealybugs might be about to move in.
Like many other insects, female mealybugs produce honeydew as they feed. This sweet liquid attracts ants for protection. Unfortunately, it also creates a perfect environment for sooty mold. Honeydew can be washed off the plant’s leaves and stems using water, but only if growers notice it before mold starts to form.
As female mealybugs suck the juices from marijuana plants in preparation to lay their eggs, the plant’s leaves may turn yellow and drop off. It’s rare for mealybugs to decimate marijuana crops, mostly because growers typically notice them before the situation becomes too serious. This gives them time to take action before the rest of their crops are affected.
How to Get Rid of Mealybugs
Since mealybugs are relatively easy to see, growers can just remove female mealybugs by hand, using a cloth to rub them off the stems. For growers who have let things get out of hand, this isn’t the best option though. Thankfully, there are a few other ways to get rid of these pests.
Spray Them with Water
If the plants haven’t been severely damaged by the mealybug infestation, growers can simply spray the whole crop off with water. This removes not just the mealybugs but also their webbing and honeydew, reducing the chances of mold development and taking away a vital food source from the ants that would otherwise flock to the area to protect the pests. If the plants aren’t in good health, spraying them with a hard stream of water can do more harm than good, though, so be cautious when using this method.
Spraying the bugs off with water will only reduce their populations. It won’t eradicate them completely. This control method works best when combined with other organic or chemical controls.
Use Rubbing Alcohol
Growers can use small amounts of rubbing alcohol to kill mealybugs. Just put some alcohol on a Q-Tip or a cotton swab, then swab the bugs and their residue off the plants. This isn’t a great option for organic growers, but it is quite effective.
Those dealing with substantial infestations can mix rubbing alcohol with water to create a spray for easier application. Just mix eight parts water with two parts alcohol, then apply it directly to the parts of the plant impacted by mealybugs. The alcohol will evaporate when it’s exposed to air, so there’s no need to worry about residues.
Apply Insecticidal Soap
Insecticidal soaps are usually organic, so they’re perfect for growers who don’t want to deal with chemical inputs. The downside of these products is that they don’t stay on plants for long, so they’ll need to be reapplied periodically until the bugs are gone. Avoid applying soap directly to the buds, as it can alter their flavor and aroma profiles.
Use Diatomaceous Earth
Diatomaceous earth (DE) is a naturally occurring substance used to control a wide variety of insects, including mealybugs. This mixture of crushed sedimentary rock works by puncturing the insects’ exoskeletons and absorbing their bodily fluids, causing desiccation. DE won’t harm plants, but it may impact other native insect populations, including some beneficial predatory insects.
Introduce Predatory Insects
All insects have natural predators, and that includes mealybugs. If the concentration of natural predators like ladybugs, lacewings, and lady beetles aren’t high enough to keep the infestation at bay, growers can introduce more of them. They can be purchased from garden supply stores or online. Just keep in mind that predatory insects will only stay around for as long as they can find prey. Once the mealybug population is under control, ladybugs, lady beetles, and lacewings will fly away to look for greener pastures and growers may be left facing a second infestation.
Apply Neem Oil
Neem oil repels many species of insects, including mealybugs. For best results, apply it in the evening or on a cloudy day so it doesn’t evaporate immediately and make sure to coat all parts of the plant, except for the buds. Neem oil and other horticultural oils can leave behind an unpleasant taste and smell, which can ruin an otherwise good crop when they’re applied directly to buds.
DIY Horticultural Oils
Growers don’t have to buy horticultural oils from the store. Homemade concoctions can work just as well. Just mix five tablespoons of Castile soap with two tablespoons of olive oil and a gallon of water, then add control agents as needed. Cinnamon, garlic, and red pepper are all great at eradicating mealybugs when used in horticultural oils.
There are some chemical insecticides that effectively reduce mealybug populations. Look for one that contains bifenthrin as an active ingredient. Make sure not to apply chemical insecticides immediately preceding harvest, though.
Want to take preventative measures instead of waiting until the mealybug population gets out of control, or need to follow up on eradication measures to make sure the plants don’t get infested again? Those are both great ideas. There are a few easy steps growers can take to prevent mealybug infestations.
Keep Ants in Check
Since ants and mealybugs have a symbiotic relationship, keeping the ants in check can substantially reduce mealybug populations. DE, described above, is great at keeping ants at bay. Apply it around the perimeter of the garden and near any ant trails or nests.
Buy Better Seeds
Buying high-quality seeds can help to prevent all kinds of insect infestations. Healthy plants grown from high-quality seeds have better pest resistance, which means they’ll be less susceptible to damage from mealybugs. There aren’t any strains of marijuana that are completely mealybug resistant, but healthy plants will be better able to fend off these pests and recover from the damage they cause.
Move the Plants After an Infestation
If the garden has already been infested with mealybugs, growers should take action to control them quickly before they spread. Once they’re confident that the insects are completely gone, those who grow in pots should move their plants to new ground. This helps to prevent reoccurring infestations. Outdoor growers who plant directly in the ground don’t have this luxury, but they can still move their crops the next year.
Mealybugs can stay alive in the crevices of plant pots and garden tools for quite some time. Growers should wash their tools and plant pots with water or alcohol after tackling an infestation to prevent the pests from coming back. It’s also wise to replace the soil in potted plants, as they can also remain dormant in soil.
What to Expect from Mealybug Control
While indoor growers have highly controlled environments that they can, with some extra effort, keep completely free of mealybugs and other pests, outdoor growers shouldn’t expect to never see a mealybug again after taking control measures. Seeing one or two mealybugs in a garden is nothing to panic about. Just remove them using one of the methods above and stay vigilant about inspecting plants for signs of growing infestations.
The Bottom Line
Mealybugs aren’t the most destructive of cannabis loving agricultural pests, but growers still can’t afford to ignore them. Keep an eye out for early signs of infestation like white, cloudy webbing in the crevices of stems and leaves and remove any mealybugs immediately to stop them from spreading. Growers should only need to take more drastic measures if the mealybug population is already out of control.
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