Aphids: 10 Tips for Getting Rid
Aphids can become a real scourge in muggy conditions. The sap-sucking insects leave behind a sticky honeydew on which sooty molds grow. With these tips, you can get rid of the pests in an environmentally friendly way.
Each year, aphids make life difficult for many garden plants. They often appear in large numbers and sit close together on the shoot tips. These ten tips will help you get rid of aphids in an effective and environmentally friendly way.
Aphids tend to infest young leaves and shoots: The cell tissue is still soft here, making it particularly easy for them to get to the plant’s coveted sugary sap. At the same time, it is easy to get rid of aphids because most plants don’t mind if you simply cut off the affected shoot tips with garden shears. With some herbaceous perennials, such as the great bellflower (Campanula latifolia var. macrantha), you can also prevent self-seeding by pruning them after they flower.
The whitefly tends to wreak havoc in the greenhouse damaging and tomatoes among others. You can control infestations by hanging up yellow traps when planting. Once the first whiteflies have been caught, remove the traps and use special parasitic wasps (Encarsia) to parasitize the pests. You can order these from specialist retailers and have them sent by post. Simply hang the little cards with the parasitic wasp pupae on the affected plants.
Ladybugs and their larvae are the most effective helpers when it comes to pest control. The adult insects kill up to 90 aphids a day and the larvae can devour as many as 150. Hoverfly larvae manage 100 aphids a day, while aphid lions – the larvae of the green lacewing – can take on 50. Predators multiply strongly if there is a good food supply, so a balance is usually established within a few weeks of the initial mass outbreak of aphids. Avoiding pesticides is not the only way to promote beneficial insects, you can also use insect hotels, lacewing boxes, and lots of flowering plants – adult lacewings and hoverflies feed exclusively on nectar and pollen.
It’s not only vampire hunters that swear by – sucking insects with a vegan diet, such as aphids, also dislike the smell. Many hobby gardeners have noted that putting a few cloves of garlic deep into the root ball can protect house and balcony plants against aphid infestations. However, this only works as a preventative measure – if the irritating pests have already settled on the plant, it is too late. A rhubarb leaf broth can be helpful against the black bean aphid in this case: Boil 1lb of leaves in three liters of water for 30 minutes, strain the liquid and spray the affected plants a few times at intervals of one week.
Most species of aphid lay their eggs on shrubs at the end of the season and the new generation hatches in the following season. Depending on the species, the adult insects also overwinter on different trees and shrubs. With fruit trees, using a brush to thoroughly wipe down the trunks in late fall before they are painted white has proven an effective way of removing overwintering lice and their eggs. In winter, spraying the entire plant with a vegetable oil insecticide is also advisable: A film of oil covers all remaining aphid eggs, preventing the exchange of oxygen and killing the insects off.
You can also tackle aphids without using highly toxic chemical agents – such as with biological products containing rapeseed oil (Naturen) or potassium soap (Neudosan Neu). They work by clogging the insects’ respiratory organs (trachea) with tiny droplets of oil. Before using the product, test it on two or three leaves to find out if your plants tolerate the treatment: The products can damage the leaves of species with thin, soft foliage.
As the winged generations of aphids do not appear until the summer months, the pests are not very mobile in spring. If only a few of the plants on your balcony are affected, you can generally remove the aphids from them in good time with a few blasts of water. Even if they land on the ground just a few inches away, they’re no longer able to crawl back onto the plant. However, this does not work for aphids that are firmly attached (see tip 8).
Potted plants like oleander and citrus fruits are susceptible to scale insects. These insects are only mobile at an early stage of life. They later settle in one place, remain there under their protective cover and start feeding from the sieve tubes of the plant. They are often so well camouflaged that they can only be identified by their honeydew secretions. Mild infestations on smaller plants can simply be scraped off with the edge of a wooden stick or a thumb nail. For more severe infestations, you should cut off the younger shoots and compost them. Scale colonies on older parts of shoots should simply be dabbed with vegetable oil: A film of oil clogs the respiratory organs and suffocates the scale insects.
The black bean aphid is widespread in vegetable gardens – besides beans, it also infests potatoes and beets. Mixed cultivation makes it harder for the aphids to transfer to other plants, provided that the host plants are not growing in rows that are directly next to each other and you leave a generous distance between the rows of plants. Sow and plant across the prevailing wind direction so that the young insects (nymphs) are not easily blown onto neighboring plants in the same row
As a plant nutrient, nitrogen primarily stimulates the growth of shoots and leaves, but the tissue is left relatively soft and unstable. High doses of this mineral fertilizer provide aphids with a luxurious feast: Firstly, making it easier for the insects to get to the sap through the soft tissue, and secondly, this sap contains plenty of proteins and amino acids due to the good supply of nitrogen.