Stopping Scale Mealybugs Before They Kill Your Marijuana Plants

If your marijuana plants’ leaves are curling up, showing signs of nutrients problems or drought, or plants are growing slowly and seem sick, the cause could be a very tough little pest called “scales,” or mealybugs.

They show up on the main stalk and side branches, looking kind of like little warts or bumps.

Even under magnification they don’t look like a bug the same way spider mites look like a bug.

They often look like a lump of brown, spotted crap.

Mealybugs are among the most damaging pests that harm your marijuana plants.

They come in many different varieties so it’s hard to identify them at first.

They insert their sucking mouths into your plants and suck the life right out of them.

These circular pests swell up and excrete a sweet, sticky, shiny substance called “honeydew.”

The honeydew is yet another problem, because it attracts other pests, and also provides food for sooty molds that can ruin your crops.

Scales (mealybugs) come from the outdoor environment, but are also transmitted into your grow op and onto your marijuana plants from infected plants, soil, pets, and clothing.

They like warm weather, and are particularly happy when they find stressed plants.

They start out so small you can’t see them. If you do see them, they might look like dark-colored aphids.

They’re most often found at the bottom of your plant, infesting the main stalk, side stalks, and leaves within 10-15 inches of the root zone.

They can crawl, but very slowly.

After a certain point they stop moving and fasten themselves down to suck away at your plant’s juices.

They’re often called “armored scales” because many varieties of these pernicious pests armor themselves with a gooey but hard plate that covers the real insect underneath.

Because of their armor, they’re virtually impossible to eliminate with pesticide sprays, horticultural soaps, and other spray methods.

For example, if you want to suffocate them with horticultural soap, or penetrate them with a natural pesticide, you have to spray so much on them that you also suffocate your cannabis plants.

Systemic pesticides don’t work well with scale mealybugs, and can make your crops unfit for human consumption.

Some growers try to brush them with isopropyl alcohol. This does dissolve their bodies, but it also harms marijuana plants.

One preventive that has worked to at least partially repel scale mealybugs, spider mites, and other sucking pests is to root feed and foliar spray Rhino Skin, a potassium silicate formula, at 200 ppm and with a pH of 5.7 for both root feeding and foliar spraying.

Because scale mealybugs don’t like cold and they also don’t like low humidity, you find they thrive in warm, moist grow rooms and will recede if you cool and dehumidify the grow room to something like 70F when lights are on and 65F when lights are off, with relative humidity between 51-56%

When members of our grow team have had to deal with these fat, ugly, little monsters, we ended up removing or crushing the scale mealybugs by hand.

It’s time-consuming and messy, but it’s what you have to do if you want to save your plants.

Only problem is, if the scale mealybugs have moved up the stalks and are in your buds, there’s no way to remove them without breaking up resin glands and exposing cannabinoids and terpenoids to degradation.

The presence of scale mealybugs (or any pest bodies) in your buds makes them unfit for sale as whole flower.

If we have buds that are infested with scale mealybugs, spider mites, aphids, or other pests, we nurse the plants along using B-52 vitamin booster until harvest time, then we process those buds into concentrates, alcohol tincture, and other marijuana products from which the insect bodies have been eliminated.

Some growers use beneficial predator insects to control scale mealybugs.

These include parasitic wasps, beetles, lady bugs, lacewings, and mites.

If you’re not familiar with using beneficial insects, this probably isn’t a good solution for you.

The best way to deal with scale mealybugs is by preventing them from taking hold on your plants.

It means getting down on your hands and knees with a magnifying glass and looking at the stalks and sucker stems.

Look at the picture accompanying this article and you’ll see exactly what these voracious little twits look like.

As soon as you see even one of them, crush it, remove it from the plant, and wipe off the honeydew.

Examine your stalks and stems all the way up and down your plants, especially at junctions where scale mealybugs like to hide.

Then at least twice a day take a very close look at your plants.

Scale mealybugs do have a life cycle involving eggs, so it may take you a weak of crushing and removing them to get rid of them completely, assuming that your soil or grow room isn’t totally infested so it’s a lost cause.

Note that scale mealybug can survive cold temperatures and can survive for weeks without having any plants to feed on.

If you have a serious scale mealybug outbreak in your grow op, you’re going to have to physically scrub down every surface to ensure you remove scale mealybugs and their eggs.

It does no good to fog the room with insecticide. They’ll survive, and your grow room will be coated with poison.

Know also that some marijuana strains are naturally resistant to scale mealybugs but others are magnets for them.

We’ve seen crowded grow ops with multiple strains and one strain was plagued by scale mealybugs while the strain right next to them had none at all.

We’re all familiar with spider mites, broad mites, aphids, thrips, whiteflies and other pests, but in some ways those are easier to detect and defeat than scale mealybugs.

You’ll be glad if you never see these armored suckers in your grow op.