Aphids: What are these Pests and Why You Should Get Rid of Them
Aphids are one of the most destructive garden pests in temperate regions. They damage plants by feeding on buds, fruits, soft stems, and branches. Aphids suck the sap of plants by piercing the stems, leaving behind yellowed or curled leaves, damaged fruits, or deformed flowers.
Most aphids eat various plants, but some species feed only on certain plants. Examples of such species include the rose aphid and green peach aphids.
What are Aphids?
Aphids are tiny, soft-bodied insects that produce a sugary substance called honeydew. The substance can encourage sooty mould growth, a fungal disease that causes the branches and leaves of plants to turn black. The honeydew also attracts ants and other insects that feed on the sugary substance.
Aphids are usually found on the undersides of leaves. Heavily infested leaves will turn yellow or wilt due to excessive sap extraction. Aphid feeding will usually not cause serious harm to healthy shrubs and trees. Some plants, however, are extremely sensitive to the feeding habits of certain species.
What Do Aphids Look Like?
Adult aphids are under ¼-inch long and may come in different colours such as red, green, black, brown, or yellow depending on the plants they eat and the species. They have pear-shaped bodies with antennae and long legs. Some species appear woolly or waxy due to the gray or waxy white substance that covers the surface of their body.
Adults are usually wingless, but most species can develop wings during fall and spring or when aphid populations are too high. A winged adult can travel to other plants and begin a new colony there. Aphids usually feed in large groups, but they may also attack plants in small groups or alone.
Aphid Life Cycle
Most aphids in mild climates reproduce asexually. Adult females can produce offspring without mating, but some species will mate and lay eggs in winter or fall. In some cases, they lay eggs on alternative hosts such as perennial plants to survive during winter.
In warm climates, many species can develop from nymphs to adults within 7 to 8 days. Adult aphids can produce up to 80 nymphs within one week, so their population can increase quickly.
Where Do Aphids Come From
Infestations usually result from a small number of winged adult aphids that feed on the plant. They deposit wingless nymphs on the tender tissue before flying to another plant.
The nymphs or immature aphids feed on the sap of plants and mature within 7 to 10 days. Once they become adults, they are ready to produce their offspring.
Aphid Infestation
Small populations of aphids do not usually cause significant plant damage. However, large aphid populations can stunt shoots and turn leaves yellow.
Some species also cause gall formations and transmit viruses between plants. Pumpkin, cucumber, squash, melon, lettuce, bean, beet, bok choy, potato and chard are prone to aphid-transmitted viruses.
Infested plants will often have yellow, curly, or mottled leaves. Aphids can also stunt plant growth. Some species of aphid feed on the roots and stems of plants such as the woolly apple aphids that consume the woody parts or limbs of apple roots. Lettuce root aphids, on the other hand, infest lettuce roots in summer and spring, causing the plant to wilt and die.
How to Prevent Aphids
Bug-eating birds such as chickadees and wrens can help keep aphid populations under control. You can attract them by growing shrubs and small trees where they can build their nests.
Ladybugs will also happily gobble down aphids infesting your garden. You should release them in the evening or at a dusk to prevent them from flying away. Do not forget to spray water onto your plants before you release them. The moisture may encourage them to stay in your garden. They will eventually fly away to create their colony, but they should be able to eliminate the aphid population in your garden before they go.
Parasitic wasps and lacewings can also help control aphid damage by eating aphids and other soft-bodied insects. Aphidlions or lacewing larvae can consume up to 600 aphids. Parasitic wasps do not usually eat aphids, but they do eat other insects that may infest your garden.
If you grow the right flowers and plants, you can attract these natural predators and convince them to stay in your garden for a long time. Clover, fennel, yarrow, mint, and dill can attract beneficial insects. You can also plant natural aphid repellents in your gardens such as allium, catnip, onion, garlic, and chives.
Another option is to grow plants that are attractive to aphids such as zinnias, nasturtium, dahlias, mustard, cosmos, and asters. These plants will lure aphids and other pests away from the plants that you want to protect. Do not forget to get rid of dead plant materials that may be sheltering aphid eggs and nymphs over winter.
Managing ants can also help keep aphid populations under control. Ant bait stations work well in attracting ants because the ants will bring the bait back to their main colony. This is one of the best methods for pest control as it will kill the ants at once. With fewer ants to protect them, the aphid population in your garden will drop.
How Do You Get Rid of Aphids?
There are various ways to get rid of aphids. One of these is by spraying the infested plant with a strong jet of water from a hose. This method works best during the early stages of aphid infestations. It is not suitable for delicate or younger plants, so you should only use this method on plants that can tolerate high water pressure.
Another option is to remove aphids by hand. Wear a pair of gloves and pick them off your plants then drop them into a bucket or jar of soapy water to drown them.
Organic and natural aphid sprays will work too. You can make your aphid spray by adding a few tablespoons of dish soap to a bucket of water. Transfer the mixture into a spray bottle and use it on the infested parts of your plant.
Pay special attention to the undersides of leaves. The soap will dissolve the protective outer coating of aphids, which will eventually kill them. The mixture will not harm beneficial insects and birds such as pollinating bees, lacewings, and ladybugs. Make sure that you are not using products or detergents with moisturizers or degreasers.
As an alternative, we recommend the use of Safers Insecticidal Soap RTU 1L, Safers Defender 1L RTU, or the Ortho Bug B Gon Eco Insecticidal Soap RTU 1L.
Neem oil can also repel aphids, mealy bugs, leafminers, beetles, cabbage worms and other insects. Take note that it may harm beneficial insects as well. Follow the manufacturer’s instructions on how to apply it especially if you have beneficial insects in your garden.
You can also use essential oils to treat aphid-infested plants. Mix four to five drops of essential oil with water then transfer the mixture into a spray bottle. Clove, peppermint, thyme, and rosemary essential oil will work well against aphids.
Spray the mixture on infested plants to kill adult aphids, nymphs, and eggs. But if you do not have the time or patience to make your aphid spray, you can just buy insecticidal soaps at a local nursery or online.