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!
APHIDS: What You Want to Know About Them and How to Organically Get Rid of an Aphid Infestation in Your Cannabis
Providing a Healthy Environment for Home, Garden and Body
Aphids are a common pest
Aphids in multiple life stages. Photo by W. Cranshaw, CSU, Bugwood.org
What does an Aphid pest look like?
Aphids are small, pear-shaped soft-bodied insects about 1 to 3 mm long. Like all insects, they have six legs, a pair of antenna, and three body segments: head, thorax and abdomen. There are thousands of species that vary in color from green to yellow, black or brown. Some have wings, some are covered with wax or “wool” made from webbing they secrete and others have unique distinguishing features.
Common to all aphids, distinguishing them from all other insects, are a pair of “cornicles” which extend like tailpipes from their abdomen. These can vary in length and color.
Where is the pest found?
Aphids colonize the stems and undersides of plant leaves. Some species, such as the black bean aphid, are quite noticeable because their color stands out from the plant. Others, such as the green peach aphid, are often colored spring green and blend in with young leaves.
What do Aphids do to the plant?
Aphid photo by W. Cranshaw, CSU, https://bugwood.org/
Aphids are true bugs. Like all bugs, they live on plant juices by puncturing leaves using a straw-like mouth called a proboscis to suck sap from stems, branches and leaves. In order to obtain enough protein, aphids suck a lot of juice, extract the protein and excrete the concentrated sugar solution that is referred to as “honey-dew.” The aphid excrement attracts ants that herd the suckers, protecting them from predators. Honeydew is a growth medium for sooty fungus, which causes necrosis of leaf parts.
Heavy aphid infestations cause leaf curl, wilting, stunting of shoot growth and delay in production of flowers and fruit, as well as a general decline in plant vigor. Aphids are vectors for hundreds of diseases and can quickly cause an epidemic. They transfer viruses, bacteria and fungi from plant to plant.
What you want to know about Aphids
Aphids in multiple life stages. Photo by W. Cranshaw, CSU, Bugwood.org
Aphids are true “bugs,” sucking insects in the order Hemiptera. Most aphid species have a complex life cycle. Many species overwinter as eggs, but during most of the season they are nonsexual and deliver nymphs pathogenically. These nymphs are live-birthed and born pregnant. A single species produces populations that differ depending on the season. For instance, seasonally, when infestations become dense, some populations have wings and colonize new plants by traveling on air currents. Each live-birth generation exists for only 7 to 14 days. If left unchecked, aphid populations rapidly grow to thousands.
Sexual populations appear in the fall, resulting in eggs that overwinter. All species have temperature-dependent rates of reproduction. But even at the same temperature, aphids may reproduce at different rates based on nutrition from the host plant.
Most aphids live only in the plant canopy. Root aphids, most commonly the rice root aphid, live in the planting medium and feed on the roots, making early detection and treatment much more difficult.
Indoors, with no predators to keep them in check, aphids can overrun a cannabis garden in short order.
How to prevent Aphids
Aphid photo by W. Cranshaw, CSU, https://bugwood.org/
Aphids are airborne for part of their life cycle. Use a 340 micron mesh or filter to keep them out of the grow space. A thrips screen should be used in the garden. It works on aphids as well.
Check the plants regularly for aphids—at least twice weekly when plants are growing rapidly. Most species of aphids cause the greatest dam-age when temperatures are warm but not hot (65-80°F). Inspect root zones and around the tops of pots for aphids in the media. Shaking a container can dislodge some aphids from bottom of the container. Use this technique to spot occurrence.
Catch infestations early. Once their numbers are high and they have begun to distort and curl leaves, aphids are hard to control because the curled leaves shelter them from insecticides and natural enemies.
Aphids tend to be most prevalent along the upwind edge of the garden and close to other sources of aphids, so make a special effort to check these areas. Many aphid species prefer the undersides of leaves, or tender terminating stalks, so check there.
Close up of aphids on stem. Photo by W. Cranshaw, CSU, https://bugwood.org/
Aphids usually feed on the underside of leaves or on stems. Colors include black, green and red. Once aphid infestation is identified, investigate its extent, then treat aggressively. Dead aphids leave white remains of their exoskeletons. These are sometimes mistaken for other organisms.
Outdoors, check for evidence of natural enemies such as lady beetles, lace-wings, syrphid fly larvae and the mummified skins of parasitized aphids. Look for disease-killed aphids as well: they may appear off-color, bloated, flattened or moldy. These observations should be considered when evaluating treatment strategies. Substantial numbers of these natural control factors can mean that the aphid population may be reduced rapidly without the need for treatment.
Some species of ants farm aphids, carrying them to fresh grazing areas and protecting them from predators. They collect the honeydew, the concentrated sap excreted by the aphids. If you notice ants in the picture, you will have to control the aphids.
How to control Aphids in your outdoor cannabis garden
Aphids on a cannabis plant. Photo by W. Cranshaw, CSU, https://bugwood.org/
Sometimes aphids must be controlled outdoors. Often this can be accomplished by spraying them off with water. Spraying several days apart will knock down the population considerably, reducing plant stress. If aphids remain a problem, consider one of the controls listed in the indoor section below.
Check for ants: when they are present aphids are much more difficult to control, so they must also be eliminated.
How to control Aphids in your indoor cannabis garden
Indoors and in the greenhouse aphids have an easy life. Without threats from weather and by living in a relatively predator-free area, they don’t suffer losses to these relentless killers. Without the pitfalls they suffer in nature, aphid population growth reaches exponential proportions quickly.
Since the balance of nature isn’t operative indoors, the gardener must intervene before an outbreak has reached epic proportions. There are a lot of choices:
Professionals often use parasitoids when there is an out-break that hasn’t reached epic proportions. Predators are recommended for heavy infestations. However, this may reflect professionals’ preference for aggressive predators over subtle parasites. The predators spend a portion of their life eating aphids, and close-up their actions can be as vicious and dramatic as an alligator’s.
The parasitoids inject an egg into the aphid. The egg hatches and the parasitoid larvae feast inside. Most aphids die within one to two hours of this egg-laying. The body of the aphid undergoes a dramatic change as it becomes a “mummy” changes color and bloats. Each larva emerges as an adult Alien-style from the mummy. Not quite as dramatic, except when the adult crawls out of the corpse, but every bit as effective. The old mummy remains stay on the leaf.
Aphid photo by W. Cranshaw, CSU, https://bugwood.org/
Among the most important natural enemies are various species of parasitoid wasps (such as Aphidius colemani, Aphidius matricariae and Aphidius ervi) that lay their eggs inside aphids. The generation time of most parasitoid wasps is quite short when the weather is warm, so once mummies begin to appear on the plants, the aphid population is likely to be reduced substantially within a week or two. These wasps are tiny and do not have stingers so they pose no threat to people or pets.
Many predators also feed on aphids. The most well-known are the common lady beetle (Hippodamia convergens), green lacewing (Chrysopa rufilabris) and predatory flies (Aphidoletes aphidimyza, Aphidius colemani, Aphelinus abdomi-nalis, Aphidius ervi). Naturally occurring predators work best, especially in small backyards. Commercially available lady beetles may give some temporary control when properly handled, although most of them disperse away from the yard within a few days. They are most effective in protecting large areas rather than small plots, which they are likely to leave in search of dense prey infestations.
Aphids are very susceptible to fungal diseases when it is humid. Whole colonies of aphids can be killed by these pathogens when conditions are right. Look for dead aphids that have turned reddish or brown; they have a fuzzy, shriveled texture unlike the shiny, bloated, tan-colored mummies that form when aphids are parasitized.
How to make an organic pesticide recipe using the dead aphids
Make a pesticide by taking these dead aphids, blending them with water (1-3 teaspoons of aphids per quart) and spraying the solution on plants.
Aphids photo by W. Cranshaw, CSU, https://bugwood.org/
There are also biological controls of aphid infestations
• Beauveria bassiana (beneficial fungi) • Capsaicin • Carbon dioxide • Cinnamon oil • Cloves • Coriander oil • Garlic • Horticultural oil • Insecticidal soap • Neem oil • Peppermint oil • Pyrethrum • Soap • Vacuuming
Ed Rosenthal Recommended Products
Vital Oxide is a EPA registered disinfectant that eliminates mold, mildew as well as bacteria and viruses and can be used on a wide range of surfaces, from light deprivation tent fabrics to grow pods and trays and utensils. Vital Oxide does not corrode surfaces or articles treated so no need to worry about discoloration or rust. Vital Oxide also has a NSF rating for food contact surfaces without rinse or wipe needed, this feature is useful in areas like kitchens, cutting boards and countertops to avoid cross contamination. Vital Oxide is a one step disinfectant cleaner with a great safety profile, contains no VOC (Volatile Organic Compounds) and is a powerful odor eliminator.
SoluNeem is not neem oil but the first organic water soluble neem powder. Soluneem is 100% water soluble so there is no need for emulsifiers or detergents, just add 1 tsp to 1 gal of water and you can cover 1000 sq. ft. OMRI rated organic, Soluneem has no problems eliminating aphids, thrips, white flies, caterpillars, etc. without causing damage to any of the beneficial insects. At 6% Azadiractin concentration, is about 33 times more concentrated than regular neem oil products. No need to deal with sticky residue or many of the issues that neem oil seem to present. Soluneem is easy and quick to use, as well as safe. Soluneem is very versatile because it can be applied as foliar application as well as root drench or through systemic irrigation up to the day of harvest with no phytotoxicity.
Aphids are true “bugs,” sucking insects in the order Hemiptera. If left unchecked, aphid populations rapidly grow to thousands. Indoors, with no predators to keep them in check, aphids can overrun a cannabis garden in short order.