Aphids: How to Get Rid of Them and Protect Your Harvest
Aphids are among the most common insect pests that gardeners may encounter. They most frequently attack plants grown outdoors in beds, on balconies or in greenhouses, but they can also find their way into indoor growing rooms. Aphids can cause considerable damage. In addition to damaging leaves, they transmit disease pathogens, and their honeydew is an ideal breeding ground for mould. Let us look at how to identify aphids, protect plants against them and get rid of them effectively.
What are aphids and why are they so dangerous?
Aphids are tiny sap-sucking insects from the aphid family (Aphididae). There are hundreds of species that attack a wide range of useful plants. Adult aphids measure 1–4 millimetres and may be green, yellow, black, brown or even pink, depending on the species and age. Some aphids have wings.
Aphids harm plants in several ways. They feed by sucking sap, which weakens the plants and leaves small wounds that provide an entry point for pathogens and diseases. Some aphid species are also vectors of viral diseases. All aphids excrete sticky honeydew, which attracts ants and often causes mould to spread.
Aphids thrive best at temperatures of 20–25 °C, and in Czech gardens they are most commonly encountered during June and July. Under favourable conditions, aphids can reproduce incredibly quickly, and within a few weeks a colony numbering thousands of individuals may develop.
You may also be interested in: How to combat insect pests
How to recognise an aphid infestation
Aphids usually live on the underside of leaves, but you may find them all over the plant. They often hide in folds on leaves and stems, where rain and sprays cannot reach them. Typical signs of an aphid infestation include sticky honeydew trails and the presence of ants on the plant. Aphids also excrete salty toxins while feeding, which cause the leaves to curl.
- Curled or distorted leaves caused by the salty substances in aphid saliva.
- Shiny honeydew trails, which attract ants and provide a site for mould to multiply.
- Slowed growth and yellowing leaves and overall plant weakness.
- Black mould (sooty mould) on areas covered with honeydew.
Natural methods of combating aphids
Aphid infestations can often be prevented and dealt with using natural methods. As with all insect pests, the foundation of protection against aphids is proper plant care, preventive sprays and biological control.
Mechanical removal: Smaller colonies can simply be washed off with a jet of water or wiped away with a cloth. It is better to cut off heavily infested parts of the plant.
Biological control: The natural enemies of aphids include ladybirds, their larvae, lacewing larvae, hoverflies and parasitic wasps of the genus Aphidius. Products containing predatory mites provide effective protection in greenhouses and indoor growing rooms.
Preventive sprays against aphids: Throughout the entire vegetative phase, we recommend regularly treating plants with a universal protective product, such as Canna Cure, BioBizz LeafCoat or another biological spray.
Products against aphids
In cases of more serious infestation, pesticides in the form of sprays are the most effective against aphids. However, as always, gentler natural options and highly effective synthetic alternatives are available. It is important to remember that pesticides must never be used on flowering plants whose flowers are intended for consumption or further processing.
Natural sprays and soaps against aphids
Contact products based on plant oils and extracts, potassium soaps and biological sprays are highly effective against aphids.
- Neem oil: Biocont NeemAzal
- Oil emulsions: Rock Effect
- Biological sprays: BioBizz LeafCoat, Canna Cure, NATURA, BHB MM
Chemical sprays against aphids
You may also be interested in: How to get rid of spider mites
For further advice on combating pests, as well as more tips and tricks for indoor and outdoor growers, visit our Higarden blog.