How to Identify Aphids on Cannabis Plants (also called greenflies and blackflies)
Aphids are soft-bodied insects which can appear white, green, yellow, black, brown and red, depending on their stage of life and where you live. Because they’re so widespread they can be a cannabis pest almost anywhere in the world!
Aphids look very different depending on their stage of life. In this picture, the bigger, rounder bugs are adult aphids, while the white, smaller, thinner bugs are young aphids (nymphs). Note: If you’re seeing white bugs that look like tiny fat worms, you may actually have thrips.
Sometimes the aphids that attack marijuana are dark colored or black. This bud is aphid city!
Sometimes when growers see tiny black flies or green flies on their cannabis, they’re actually seeing aphids with wings. Winged aphids can be dark or pale, and colors include green, red or yellow. However, the general body shape of the bug is usually pretty similar whether the aphids have wings or not.
Because many aphids that attack cannabis are green, sometimes people don’t recognize aphids when they’re a different color (like these young aphids which appear red)
These aphids from Europe are pale green with dark legs and red eyes
Aphids are a common cannabis pest. Adults are usually small and oval-shaped and may have visible wings or antennae. Nymph aphids are thin/long and usually white or pale. Because nymphs are so small, they may look like little white specks or eggs.
Aphids pierce cannabis leaves with their sucking mouth-parts and feed on the juices inside. They usually occur in colonies located mainly on the undersides of stems and leaves. If a cannabis plant becomes heavily-infested, its leaves can turn yellow and/or wilt due to the excessive stress and leaf damage.
“Honeydew” and Black Sooty Mold
Another problem with aphids is they produce large amounts of a sweet substance known as “honeydew,” which is a sugary liquid waste. Honeydew drops from these insects attract a type of fungus called sooty mold. Sooty mold can grow on honeydew deposits, accumulating on the leaves and branches of your plant and turning them black. Not only does this mold discolor the plants and somewhat hinder normal plant processes, sooty mold on buds can make them unsafe to smoke. And just to be an extra pain in the butt, the drops of sweet honeydew can also attract other insects such as ants.
What Causes an Aphid Infestation?
Your plant can become infested when winged “colonizer” aphids land on the plant and lay eggs. Although you may not see the winged version of an aphid actually eating your plant, they are still dangerous because they can lay eggs and start a new aphid colony! Winged aphids are sometimes called “blackfly” or “greenfly” bugs depending on the color (because they are often black or green/yellow, and they look like tiny flies).
Aphids are sometimes called “Green Flies” or “Black Flies” when they have wings, but the general body shape is the same. The winged versions appear when the aphid colony gets too numerous and these bugs use their wings to fly away and lay eggs on other plants. This “black fly” is actually a winged aphid.
This “green fly” is another color variation of a winged aphid
It’s difficult to prevent aphids from getting to your cannabis plants outdoors as just a handful of winged aphids is all it takes to start an infestation. The eggs soon hatch into a juvenile form of aphids called “nymphs,” which happily start munching on your plant.
This grower started seeing white specks on their buds and thought it might be mold or bud rot. The specks were actually white aphid nymphs. Click the picture for a closeup!
Immature aphids (nymphs) usually appear white and feed on plant sap while they gradually increase in size.
The aphid nymphs mature in 7 to 10 days and shed their skin, leaving silvery exoskeletons behind on your plants. Note: If you see tiny white bugs but they look round, fat and more worm-like than these ones, you may actually have thrips.
The bottom center aphid is actually in the middle of shedding its exoskeleton in this pic.
After reaching their wingless adult form (aphids don’t grow wings when actively colonizing your plant) they are soon ready to give birth to live young and start the process over again. Most aphids in this form are female, and each one is capable of producing dozens of offspring.
Because of their quick reproduction, a few winged aphid “colonizers” can lead to hundreds or even thousands of aphids on a plant in just a few generations. A full-blown aphid infestation can get out of control in just a few weeks!
Aphids often keep reproducing on the plant until the plant becomes so stressed (or the conditions become so crowded) that the plant can no longer support their ravenous appetites. At that point, some of the aphids start being born with wings, and these winged aphids fly off in search of a new host, starting the process over again on a new plant victim.
Solution to Aphids: Get Rid of Them Quick!
Avoid using nervous system insecticides, such as malathion, Dursban (chlorpyrifos), and Orthene (acephate). They are labeled for use on many shade trees and ornamental plants for aphid control, but are not safe to use on cannabis. If something isn’t safe to be used on edible plants, then chances are it’s not safe to use on cannabis.
1.) Check regularly for signs of aphids
The best way to prevent an aphid infestation is to catch it as soon as possible. When growing outdoors it’s pretty difficult to predict when winged “colonizer” aphids will appear, so it’s incredibly important to examine your plants at least weekly to make sure they don’t become infested while you’re not paying attention.
Examine the bud area and undersides of the new leaves for clusters or colonies of small aphids (or any other types of bugs). The presence of these colonies indicates that the aphids are established on the plants and their numbers will begin to increase rapidly.
2.) Remove or Spray Off As Many Bugs As Possible
If your plant is heavily infested, it’s a good idea to try to cut down their numbers in every way possible. Depending on the infestation, one way to do that may be to simply move your plants outside and spray as many bugs off as you can with a power sprayer. It’s also a good idea to remove leaves and buds that are heavily infected.
If possible, spray off as many bugs as you can!
3.) Insecticidal soaps
Fatty acid salts or insecticidal soaps can be a good choice against aphids. They weaken the outer shell of aphids but are safe to use on your plants and they don’t leave much of a residue.
With soaps, coverage is very important as it does not stay on your plant for long, so follow-up applications may be necessary. Although this is considered safe, avoid getting any on your buds!
4.) Neem Oil
Neem Oil will leave an unpleasant taste/smell on buds when used to treat flowering plants, so again, don’t let this stuff get near your buds! There’s also some evidence Neem oil may be harmful to humans so use with care! That being said, Neem oil is an all-natural remedy that is very effective against many different types of bugs and mold. You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly, since neem oil and water can separate easily.
Spinosad Products (safe & organic) – Spinosad products are organic and completely harmless to pets, children, and plants. Spinosad products can be used directly to kill aphids on contact and should be sprayed liberally anywhere you see aphids and especially under the leaves. Although maybe not as strong against pests as some of the more harsh insecticides, it does work and it’s very safe for plants, animals and humans!
Spinosad is an organic insecticide made from the fermentation of a specific soil bacteria (actinomycete Saccharopolyspora spinosa) and kills aphids via ingestion or contact by effecting the insect’s nervous system. Spinosad can be a good choice for organic and outdoor growers, because it is very toxic to aphids, but is less toxic to many beneficial insects and spiders.
Note: Most spinosad products are effective for only about 24 hours after being mixed with water, so only mix as much as you will need per application. Anything left over will be waste.
You will need a mister (also called a “One-Hand Pressure Sprayer”) to cover all the leaves evenly when spraying them with spinosad products.
6.) Essentria IC3
Essentria IC3 Insecticide is a mix of various horticultural oils that is organic and safe for humans. It is often marketed as a “bed bug killer” but it can be effective against aphids when the plants are treated regularly. Unfortunately it only stays effective on the plant for about 8 hours so you will want to either apply this daily or combine with other options. You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.
7.) Beneficial Insects
Beneficial insects, such as lady beetles, lady bugs, and lacewings may eat large numbers of aphids and are welcome guests in the garden. Although you can order ladybugs to release around your plants, they tend to fly away in just a day or two. Additionally, the reproductive capability of aphids is so great that the impact of the natural enemies may not be enough keep aphids at or below acceptable levels after an infestation has already gotten started.
Ladybugs are good to have around the garden – they eat aphids and other annoying cannabis pests!
Many other “lady bird” type beetles also eat aphids
This scary looking black bug is actually a young ladybird larvae, so don’t kill it! They devour aphids as youngsters too, so it’s good to let them do their thing 🙂
Good bug! Eat those aphids!
8.) Get rid of ants if you see them!
In some cases, ants naturally “farm” (tend to) aphids in the wild in order to collect their honeydew. How crazy is that? Ants can actually be helping keep your aphid numbers up! So for some cannabis growers, controlling an ant problem can actually help control an aphid problem.
If you have ants, get rid of them! They can make an aphid problem worse!
- Bronze or brown patches
- Brown or slimy roots
- Brown or yellow leaf tips/edges
- Buds dying
- Buds look odd
- Bugs are visible
- Curling or clawing leaves
- Dark leaves
- Drooping plant
- Holes in leaves
- Mold or powder
- Pink or purple on leaves
- Red stems
- Shiny or smooth leaves
- Spots or markings
- Twisted growth
- Wilting leaves
- Yellow between leaf veins
- Yellow leaves
This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.
Learn how to identify and get rid of aphids (aka greenflies /blackflies) and prevent them from ever attacking your cannabis again!
How Can I Kill the Aphids on a Bud?
Aphids can wreak havoc on plants when their numbers grow out of control. These small insect pests cluster on buds, shoots, leaves and stems, piercing tender parts of plants with their needle-like mouth parts and sucking out the plants’ sap. The shoots of heavily infested plants are stunted, and the leaves may turn yellow and curl up and become distorted. Many species of aphids infest plants, but the control and management methods are similar.
How to Identify Aphids on Your Plants
Before setting out to control the aphids on your plants, check that you’ve made the correct identification, or your control attempt may be ineffective. Aphids are small, soft-bodied insects that are roughly pear-shaped. Their colors vary, depending on the species, and they include green, red, black, yellow and brown. Some aphid species are covered in a waxy or woolly coating.
Most adult aphids do not have wings, but in most species, wings develop at certain stages of the life cycle to enable the insects to disperse more widely. You’re most likely to spot winged aphids in spring or fall or when the population numbers are at their highest. A body structure that’s unique to aphids that can be used to make a clear identification is a pair of tiny tube-like protrusions at the rear of the insect, called cornicles.
Aphids most often feed in groups, though you may spot single insects. You’ll see clusters of aphids on your plants, perhaps in a range of sizes due to the presence of adults along with younger insects. Some species are root aphids, which live and feed on the roots of plants. When disturbed, aphids move slowly, unlike other insect species that look similar.
Controlling Aphids Without Chemicals
When you’re growing food for your family, you may be reluctant to reach for a commercial insecticide spray when you spot aphids on your vegetables or fruit trees. Or, you may simply want to avoid introducing artificial and potentially harmful chemicals into the environment. Whatever your motivation, your choice brings benefits to your garden and the effectiveness of your aphid control.
Many insecticides are broad-spectrum, which means they destroy most insects, including beneficial species that prey on aphids. If you spray your aphid-infested plants with a broad-spectrum insecticide, you could be killing the insects that were helping to keep the aphid population under control. Consequently, as soon as the spraying stops, you see an increase in the number of aphids, and the infestation becomes worse than ever.
Rather than spraying an aphid infestation, use one or more alternative, non-chemical control methods.
- Check your plants regularly for aphids, and blast off any small colonies with a strong jet of water from a garden hose.
- Prune infested leaves and stems and destroy them, wiping your pruning shear blades with rubbing alcohol before and after pruning to avoid spreading the pests.
- Remove weeds in your garden, which can harbor colonies of aphids.
- Avoid applying too much nitrogen fertilizer to your plants – the soft, sappy growth that overfertilization fosters is attractive to aphids.
- Seedlings are vulnerable to attack by aphids, so sow seeds in pots in a greenhouse and transplant young plants into your garden beds.
- Remove weeds and spread a reflective, silver-colored mulch over bare soil under your plants to repel aphids. Bury the mulch edges in soil to prevent it from being blown away.
- If you can also see ants crawling on your aphid-infested plants, wrap a band of sticky ant-deterrent around the trunk, stem or container, which prevents the ants from farming the aphids’ honeydew and protecting them from predators.
- Wait for predator numbers to increase sufficiently or temperatures to rise to provide natural control.
Chemical Control for Aphids
Large, established plants can often tolerate aphid colonies and suffer no long-term damage, but if an infestation becomes serious and non-chemical control methods aren’t working, it may be time to turn to chemical control. Insecticidal soaps and oils are the least harmful chemical controls for aphids. They destroy the pests by coating them in a thin layer of soap or oil and preventing them from breathing, though they aren’t effective on aphids that hide within distorted or curled leaves galls. To apply an insecticidal soap or oil, follow these steps:
- Dilute the product according to the instructions on the product label.
- Test a small area of the plant and wait two or three days to check that it isn’t sensitive to the soap or oil.
- Spray all parts of the plant, especially the undersides of leaves.
- Regularly spray the plant as advised on the product label to keep the aphid population under control.
- Don’t spray when the temperature is higher than 90 degrees F.
- Don’t spray drought-stressed plants.
Chemicals in commercial products that, unfortunately, control aphid predators as well as aphids include acephate, permethrin and malathion. These chemicals possibly kill bees, too, and they aren’t safe to use on food crops. Another chemical that controls aphids is the systemic insecticide imidacloprid, which is applied to the soil around the plant and absorbed through the roots. Imidacloprid also destroys aphid predators and other beneficial insects.
When applying an insecticide to control aphids, carefully read and follow the instructions on the product label. Wear protective clothing, including long pants, closed shoes, a long-sleeved shirt, gloves and safety goggles. After applying the insecticide, store the container in a place inaccessible to children and animals.
Aphid Control in Hemp Crops
In states where growing hemp (Cannabis sativa, hardy in U.S. Department of Agriculture plant hardiness zones 8 through 11) is legal, new growers may struggle to control this pest. Hemp aphid control is similar to controlling aphids on other crop plants, though each state has its own regulations regarding the allowable chemical controls. As with all crops intended for human consumption, cultural controls should be the first resort.
A soil drench of a chemical called azadirachtin may be effective against aphids in hemp crops. This systemic insecticide, which is applied as a soil drench, is available in products such as AzaMax for aphids. Another potential solution to aphid infestations is the fungus Beauveria bassiana. High humidity levels are required for this biological control to work, so it’s most effective inside greenhouses.
Root aphids as well as aphids that feed above ground can infest plants. These pests look similar to their leaf-piercing cousins, but they differ in the damage they cause. If a plant’s leaves turn yellow and wilt or circles of plants in a crop collapse, the problem could be due to root aphids. Other symptoms include a white waxy substance or mold on the plant’s roots and a short taproot that sprouts many fine root hairs.
Controlling root aphids involves growing a different crop in the same patch of groun*d* each year, planting early, encouraging strong growth with fertilization, regular watering and removing weeds. Clean spades, garden forks and other gardening equipment after using them in the affected soil, and turn over the soil at the end of the growing season to expose the aphids and eggs to birds. Avoid using soil drench insecticides, which kill aphid predators that live in the soil.
How Can I Kill the Aphids on a Bud?. Aphids that infest a leaf or flower bud cause stunted, distorted growth, but a strong jet of water usually removes them. Small, pear-shaped, sap-sucking insects, aphid numbers increase in spring and fall but reduce when natural predators eat them or the weather turns hot or cold. …