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White aphids on cannabis plants - how to spot and treat them

Lucy Starley
October 19, 2023
10 min read
Small colony of aphids on the underside of a leaf
Small colony of aphids on the underside of a leaf
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Whether you are new to growing indoors or a seasoned professional, one thing is for certain – you can’t take your eye off the ball with pest control!

One of the most common pests to plague our grow rooms are the white aphid. Secondary to those are black aphids, which are very similar. If you’ve not experienced an aphid attack yet then count yourself lucky.

There is no surefire way to keep your plants safe from white aphids. But there are many ways you can prevent white aphids from making themselves at home on your plants.

If it looks as though white aphids have already arrived then fear not. Check out our tips on how to get rid of them quickly and effectively. Don’t let the pests win!

Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis you’re doing so in accordance with the law and subject to appropriate permissions and licenses of the applicable country.

What are white aphids?

The Aphididae family is a large one, made up of around 5,000 different species. Several hundred of these species are particularly problematic in agriculture and gardening environments.

Do you see now why you’d be lucky not to have come across them yet!?

What do white aphids look like?

Aphids are small, pear-shaped, soft-bodied insects. Because there are so many species of aphids, they can appear in many different colours.  Aphids can be coloured green, red, black and white.

As with many pests, white aphids are really small, they range anywhere between 1/16 to ¼ inch long. They have six legs, a pair of antennae and three body sections. These body parts are only visible under a magnifying device. So don’t worry if you can’t see all that with your eyes!

Newborn aphids, also known as nymphs are even smaller so they are incredibly hard to spot!

Generally, white aphids are wingless to start with, however, if a population gets really large, white aphids can develop wings. Winged aphids are much better at moving to new, lesser populated feeding grounds.

One distinguishing feature that white aphids have is cornicles that extend from the end of their body. These look like two tubes, or tails.

Macro shot of aphids

How to spot white aphids?

White aphids will usually hang out on the undersides of your plant’s leaves or on the stems. Aphids live in colonies. It is likey that you will spot significant numbers of them rather than a lone beast!

Aphids shed their skins around four times before adulthood. As they do this, they leave behind their skins which resemble white flakes.

When you have a large population, these dead skins can appear to be pests in themselves. But they are in fact harmless. So make sure to really check your plants before getting worried about a secondary invasion!

What is the white aphid life cycle?

In most cases, white aphids reproduce asexually. Only in colder climates do white aphids mate and lay eggs during the autumn and winter seasons.

When reproducing asexually, multiple generations can be born in the same year. This means its likely that aphids will inhabit your plants in large numbers. Adult female white aphids can birth around 80 offspring per week via parthenogenesis. Now, that’s reproductive efficiency right there!

Female’s that have been mating will lay eggs on a plant in the colder seasons.  This allows aphid eggs to develop over the winter in readiness for action when the warmer season begins. Often females will lay their eggs and then move to another plant to repeat the process. This is one of the reasons that aphid populations can grow so large.

Nymphs (baby aphids) are born pregnant and can grow into adults in just 7 or 8 days. So there really is no hanging about with aphid invasions!

Are white aphids harmful?

Much like mealybugs, white aphids feed on the juices inside the leaves and stems of your plants. Then they secrete a sticky substance called honeydew. White aphids particularly like succulent new growth.

The telltale signs that there might be white aphid damage on your plants are:

  • Misshapen leaves
  • Yellowing leaves
  • Curling or stunted leaves
  • Sticky honeydew residue
  • Dropping leaves

Just like the honeydew created by mealybugs, white aphid honeydew can attract other insects such as ants. A trail of ants can often lead you to an aphid population!

If left untreated the sticky honeydew substance can encourage the growth of sooty mould and fungus. It’s really important that you spot and treat white aphids quickly and effectively to avoid this.

White aphids are also known to carry many different plant diseases that can spread quickly. This is another reason to get rid of aphid infestations as soon as you can.

How to prevent white aphids

As with any pest problem, prevention is preferable to treatment. However, it’s easy to be caught out by sneaky pests such as white aphids, or black aphids. This is especially true with the multitude of tasks that we have to do as indoor growers.

The good news is that there are plenty of practices you can put in place to repel aphids. Prevention methods tend to be much kinder to your plants and the planet than treatment methods are. So it’s really important to try and stay ahead of the game with white aphid control.

Healthy plants

Keeping strong, healthy and robust plants is the first step to avoiding pests such as white aphids. That’s why using a grow room monitor is so important. Plants that are weak or stressed are naturally more likely to suffer from pest damage of any kind.

This means that sometimes it’s best to cut your losses and let go of any plants that are struggling. Otherwise, they can easily become the entry point for pests to invade your grow space. A tough call as a grower but often a necessary action.

As well as the health of your plants, the health of your soil is important. It’s good practice to regularly test your soil and amend it if needed. This ensures that your plants have the best possible foundation to grow in. Overusing fertiliser and over or under-watering plants are both things that can attract white aphids to your plants.

If you already have white aphids in your grow space, you can protect seedlings and young plants by using row covers.

Different types of aphids

Keep a clean grow space

Clean and organised grow spaces are calmer work environments, but they also make spotting pests a much easier task. Creating space between plants and working areas makes it harder for pests to travel around your space.

You want to dispose of any old plant debris regularly. This is often where white aphids will hide and lay their eggs to allow them to overwinter.

Keeping tools and equipment clean is also a good practice to keep on top of. Pests can enter your grow space in many ways so regularly cleaning your kit is an important part of preventing them.

Grow beneficial and repellent plants

Did you know that we can use a variety of plants to help us with pest control? The natural world is so cool, right?!

You can create naturally pest-resistant grow spaces by introducing plants that attract beneficial insects and naturally repel white aphids. Some plants can even act as white aphid traps by luring the pests away from any plants that require protection.

Plant species that are known to attract beneficial insects include:

  • Clover
  • Mint
  • Dill
  • Fennel
  • Yarrow

A bonus is that those are all edible plants. Hey, who said pest prevention couldn’t be tasty!?

Plants that act as white aphid repellents include:

  • Garlic
  • Chives
  • Catnip
  • Onion
  • Alliums

If you’re looking for a white aphid trap, then try these:

  • Nasturtiums
  • Cosmos
  • Asters
  • Zinnias
  • Dahlias
  • Mustard

Turns out pest control can be pretty too!

Diatomaceous earth

Using diatomaceous earth is a way to prevent white aphid colonies from growing. Diatomaceous earth is a fine powder made from fossilised shells.

The shells in this powder create a sharp texture that cuts into the soft-bodied white aphids. This damage dehydrates and kills them. The sharp texture is microscopic so we do not need to worry about any damage to our own hands!

Sprinkling diatomaceous earth at the base of your plants prevents white aphids from reaching the juicy plant matter. Just be aware that Diatomaceous earth is also harmful to beneficial insects such as bees and butterflies. So you do want to be mindful of how and when to use it.

Aphid infestation on a leaf

How to treat white aphids

So we’ve covered the importance of prevention methods. But unfortunately, those steps are not guaranteed to keep white aphids off your plants.

If you already have white aphids feasting on your plants then it’s important not to panic. Whilst white aphids can cause damage, there are many ways to treat them before your plants suffer too much.

So let’s start with some ways to get rid of aphids naturally:

Manual removal and pruning

Given that aphids are so small, it’s unlikely that you will be able to remove them by hand. However, if you pop on some gloves and think your plant is strong enough, you could try. Begin by wiping or knocking off any white aphid populations you have spotted.

A cotton bud can be a handy tool to use if your plants are particularly delicate. This method is only appropriate if the white aphid population is small. It’s wise to try and wipe or knock the aphids into a bucket of soapy water. This ensures that you are killing them rather than just moving them elsewhere.

Another manual option is to prune out affected areas. Make sure to properly dispose of the prunings to ensure that the aphids don’t simply move around your grow space.

Spaying them with water

If your plants are robust, you can spray them with a strong stream of water to dislodge white aphid colonies. This can work just as well for black aphid populations.

Make sure to target the undersides of your plant’s leaves when spraying with water. The undersides of leaves are the most likely home for any aphids. This process will need to be repeated every few days to be effective.

If you think your plant is too delicate to survive blasts of water then there is a gentler approach.  You can dip the entire foliage portion of the plant into a bucket of water to dislodge the aphids.

Predatory insects

Employing beneficial insects to help you with pest control is another tried and tested method. Natural enemies such as Lady beetles, Green lacewings, Parasitic wasps and predatory mites can all be used. They will set to work to reduce aphid numbers for you.

Beneficial insects can be purchased if you think that they are going to be a really effective treatment method. But, you can also encourage beneficial insects to your grow space naturally.

Lady bugs are most effective in their larvae stage as this is when they eat the most aphids. That’s why you may want to buy these rather than wait for them to occur in your grow space naturally.

You will need a fairly large white aphid population to keep ladybugs interested for long enough. You want them to reproduce to keep a steady stream of larvae munching the aphids. This is also the case with green lacewings, they are most effective in their larvae state.

Parasitic wasps are a particularly clever beneficial species, in particular Aphidius colemani, Aphidius matricariae and Aphidius ervi. They are small and stingless so they are harmless to people and pets. But they are bad news if you’re a white aphid!

You can attract parasitic wasps naturally. By planting yarrow, fennel, dill or Queen Anne’s lace you create host plants for the wasps.

When parasitic wasps come into contact with white aphids, they lay their eggs inside them. This causes the aphids to become mummified as the egg hatches and the larval wasp begins to feed. Most white aphids will die within one or two hours of an egg being laid inside them- it’s speedy work!

Whilst on the subject of other insects, it’s important to monitor ants within your grow space. Ants are not too much of a concern to your plants. But the fact that they feed on white aphid honeydew is. It means that large populations of ants can indicate that large aphid populations are present.

Magnified cluster of aphids on a plant stem

Essential Oils

There are several essential oils which can be effective in treating aphid populations. These include peppermint, clove, rosemary and thyme. Simply add a few drops of one of the essential oils into a spray bottle of water. Apply the spray to your plants regularly.

Insecticidal soap

If the natural and manual methods above are effective, then it could be time to step things up a gear. There are a variety of insecticidal methods that can be used to treat white aphid colonies.

You can begin by making homemade aphid spray, this way you can control the ingredients and tailor quantities as required.

A mild solution of water and a few drops of dish soap can be used to wipe away white aphid populations. You want to use a pure liquid soap such as Castile soap rather than anything with chemical additives, moisturisers or degreasers. Using soap is effective because it will dissolve the protective outer layer of the aphid’s body which eventually kills them. This method is not harmful to beneficial insects, so you don’t have to worry about those.

Alternatively, you can make a mix of water, dish soap and cayenne pepper. This can be applied to your plants using a simple spray bottle. When spraying make sure that you focus on the undersides of your leaves- the white aphid’s favourite place to call home.

If these homemade options are not effective enough then you may need to consider purchasing some stronger insecticidal products. These are available from your local garden centre or specialised online retailers.

There is a fungus called Beauveria bassiana. This fungus causes white aphids to suffer from White Muscadine disease, which can eliminate an aphid population. This fungus can be purchased in a spray form.

Sticky traps

Sticky traps can be used as both a treatment method and a pest prevention tool. By strategically placing yellow sticky traps around your grow space, you will catch any flying pests. This helps to eliminate the pest populations, such as white aphids or black aphids.

Another benefit of using sticky traps is that you can use them to identify other pests in your grow space. This then enables you to put effective prevention and treatment methods in place.

White aphids don’t develop wings until a colony is well established. So it’s best to use sticky traps in conjunction with other treatment and prevention methods.

Takeaways

  • White aphids and black aphids are really common pests. It’s likely you’ll come up against them if you haven’t already had an encounter
  • Prevention is better than cure. But you will need to try multiple methods before finding what’s most effective.
  • It’s always good to try natural/non-toxic treatment methods first. It’s kinder to the planet and to your plants this way.
  • White aphids live in colonies and breed quickly. So treatment methods need to be regular and repeated to be successful.

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Lucy Starley
October 19, 2023
10 min read

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