It is never pleasant to find that aphids have invaded the garden. Fortunately, they can be kept under control by arming themselves with patience and effective pesticide methods. These soft-bodied insects use their stinging-sucking mouthparts to suck sap from leaves. If you are dealing with a small infestation, you can remove them manually and try selective pruning; otherwise, you can spray a homemade organic repellent solution for a longer lasting effect. Once the problem is solved, enrich the outdoor space with beneficial plants and introduce species of insects useful to keep away the aphids that are waiting to invade your garden again.
Steps
Part 1 of 4: Identifying the Aphids
Step 1. Learn to recognize aphids with the naked eye
These tiny insects have a rounded body, equipped with long antennae and two thin tubes (called siphuncles) that extend posteriorly on either side. Depending on the species, they can have different shades of color ranging from green to yellow, gray, black, white or even pink. When viewed closely, some specimens appear to be covered in a hairy, cotton-like substance.
- Wings, when present, make these insects even more difficult to control. Some of them grow them once the food source degrades in order to fly to greener areas.
- Aphids are parasites that are widespread all over the world and tend to infest any type of crop, tree, shrub or flowering plant.
Step 2. Inspect the back of the leaves
Turn the leaves and examine them carefully for aphids. Although small, they are usually visible to the naked eye. To recognize an aphid infestation, there is no better evidence than seeing them with your own eyes.
- Although they prefer to feast on the succulent leaves of fruits and vegetables, they quietly feed on everything that grows in the earth.
- Even a small population of aphids can become a major problem for farmers and gardeners.
Step 3. Pay attention to curled or discolored leaves
Notice how often the plants seem to wither inexplicably. The activity of the voracious aphids over time weakens the plants, with the risk of making sick even those previously healthy which will thus begin to lose vigor.
- In addition to the more obvious symptoms of the disease, you may spot small bite marks along the edges or veins of the foliage.
- Aphids proliferate more in the warmer months.
Step 4. Note the presence of honeydew to identify where they feed
When aphids feed on the sap of healthy plants, they excrete a sugary substance called "honeydew". If plant leaves are oddly shiny and smooth or appear to be covered in a thin, mucus-like material, chances are there are aphids nearby.
- Honeydew can also take on a dark brown or black color when moldy.
- By periodically washing the affected plants, you will eliminate not only these pests, but also the residues they leave behind.
Step 5. Watch for galls
Once every two weeks, I inspect the plants in the garden from root to tip, looking for galls: these are growth defects that appear on the outer surface of the infested plants. They often appear due to the irritation produced by aphids when they feed and lay eggs.
- The galls can cause noticeable discoloration of the leaves, which become filled with dark growths or mold spots.
- Left untreated, galls can expose the plant to more serious diseases.
Part 2 of 4: Remove Aphids with Your Hands
Step 1. Eliminate aphids manually if it is a small infestation
With your hands, grab the insects you find on the leaves and squeeze them between your fingers. Aphids have a soft exoskeleton that breaks with light pressure. If you are dealing with more than half a dozen insects, you may want to use a damp paper towel to get rid of them more easily.
- If you are removing aphids by hand, always wear gloves to protect your skin from potentially irritating substances.
- Although aphids usually migrate to colonies in search of food, they can also show up 1 or 2 at a time.
Step 2. Wet the infested leaves with a garden hose
A strong stream of water should be enough to remove stubborn parasites. Direct it to the underside of the leaves, where aphids tend to collect. Water the plants a couple of times a day until the infestation begins to subside.
- Make sure that the water pressure does not risk damaging the plants and avoid overwatering them.
- This method is most effective for moderately severe infestations on sturdy plants with strong roots that hold them firmly to the ground.
- Let the leaves dry completely between treatments. If they stay wet, the risk of developing certain diseases such as rust is higher for moisture-sensitive plants.
Step 3. Prune the plant if you need to eliminate a large colony
Cut off the most infested parts of the plant where the greatest number of aphids are concentrated. You will likely need to remove leaves and fruit, cut off stems, or even remove entire branches. Do not leave out any insects on other points of the plant.
- Once you've trimmed the infested parts, wet the plant thoroughly with water or a homemade aphid repellent solution, such as those listed in this article.
- Selective pruning is most effective when aphids are confined to a particular area of the plant.
Part 3 of 4: Using Repellents and Pesticides
Step 1. Make a soap solution
Combine 10-15ml (2-3 teaspoons) of mild liquid dish detergent with 30-60ml of hot water in a spray bottle and shake well. Apply the mixture liberally on plants that show signs of aphid activity. The surfactants contained in the detergent will dehydrate the insects without damaging the plant.
- To make the solution even more effective, add a generous pinch of cayenne pepper.
- Store the spray bottle in the garage or near the garden so that you always have it on hand in case you need it.
- This solution also kills beneficial insects, so try to carefully select the plants to treat. To keep the spray nozzle from clogging, prepare it as often as you need.
Step 2. Try an amalgam of essential oils
Add 4-5 drops of rosemary, clove, cedar, orange, or mint oil (or make your own blend with each of these ingredients) to a spray bottle filled with water. Spray the solution on infested plants, from leaves to roots. Essential oils are natural repellents against aphids, so any insects that the pesticide doesn't kill will tend to escape.
- Essential oils have no contraindications, they keep insects away and spread a pleasant scent.
- Always dilute your essential oil blends because the oils can burn plants if left in copious amounts on the leaves. Always use the same spray bottle for this use because the oil will leave residue in the bottle.
Step 3. Buy a bottle of neem oil
Neem oil is an oily compound of vegetable origin, useful for eliminating aphids. You can buy it in its pure form and dilute it with water so that you get a 2% solution and vaporize it wherever you see unwanted insects. It will suffocate the aphids, killing them within hours.
- You can find neem oil at all major garden centers. It is non-toxic and decomposes quickly when exposed to air, so it is not harmful to people and plants.
- Another benefit of this product is its effectiveness against a host of common pests, including mealy bugs, beetles and caterpillars. That said, it kills beneficial insects and pests, so carefully select the plants to use it on.
Step 4. Apply insecticidal soap
Like neem oil and other natural pesticides, insecticidal soaps work by suffocating aphids. You can purchase these types of products at garden centers, nurseries, and outdoor supply stores. They are usually ready to use, so you don't have to worry about diluting them.
Insecticidal soap can be toxic to some types of plants, so read the directions for use on the package carefully before applying it in the garden
Step 5. Use commercial insecticides as a last resort
If the remedies you have tried have not given you any results or you are dealing with a real invasion of aphids, you need a more powerful pesticide. Choose a product known for its effectiveness against these parasites. Some come packaged in convenient spray bottles, while others are mixed and applied using a nebulizer.
- Keep in mind that chemical pesticides can be harmful to plants and beneficial predators. Always follow the instructions that accompany the product and use only the quantities indicated.
- The National Sustainable Agriculture Information Service (ATTRA) has developed a database of low-risk pesticides (including several natural options) for the benefit of farmers and gardeners.
Part 4 of 4: Preventing Further Infestations
Step 1. Introduce some species of beneficial insects into the garden
Ladybugs, hoverflies and chrysopids are just some of the insects that hunt for aphids. When added strategically in the garden, they will help you reduce the most destructive pest colonies and restore order in areas damaged by infestation.
- Typically, eggs, larvae, and even live specimens of useful predators can be purchased at major gardening supply stores.
- Ladybugs and hoverflies can also become a problem. When pitting one species against another, introduce the new beneficial insects in small numbers and keep an eye on them so they don't become a problem themselves.
Step 2. Choose plants that attract ladybugs
Make room for some plant species preferred by these insects, such as geranium, lobularia maritima, sunflower, carrot (daucus carota) and parsley. With the right choices, you can attract ladybugs to the garden without worrying about buying, introducing and monitoring them.
- Think carefully before removing the last few weed bushes. By leaving a few scattered here and there, you will help promote biodiversity in the garden. Additionally, some varieties, such as dandelion and bugle, are particularly attractive to certain ladybird species.
- Install a water source, such as an automatic sprinkler system, small fountain, or bird trough, to meet all the beneficial insects' needs. Place a small rock in the center of the fountain so that the insects can climb and avoid accidentally drowning.
Step 3. Use herbs as a deterrent
Around the plants invaded by aphids, grow species belonging to the genus allium, such as garlic and onion, but also other aromatic plants, such as ginger root, oregano and sage. Their pungent smell is a deterrent to pests that will eventually move away.
If you're looking for a quicker fix, you can cut fresh allium plants and scatter them around the perimeter of the garden instead of waiting for them to grow
Step 4. Destroy all ant colonies you see
Get rid of them using a commercial ant and destroy the mounds or nests they build to prevent their return. Ants kill many insects that feed on aphids, so the more they are around, the longer the problem may last in the garden.
Furthermore, it is known that ants protect aphids by creating real farms for these parasites by exploiting their natural secretions (the sugary honeydew) as a food source
Advice
- Once you've gotten rid of the aphids, regularly inspect your plants to prevent new infestation from occurring.
- Some flowers, such as watercress, marigold, and orange blossom, are a strong attraction for aphids. If you want to keep them in the garden, place them at a safe distance from the plants you are trying to protect to prevent these pests from getting too close.
