Aphid
Aphidoidea
Role in the garden
Sucks the sap of plants, weakens growth and transmits many viral diseases. Secretes a sticky honeydew that encourages the appearance of sooty mould (“soot”).
How to attract / manage it
Nasturtium as a trap plant to watch, releases of ladybirds and lacewings.
Practical guide
Where to find them
All sorts of plants, green aphids in the greenhouse and on fruit trees, black aphids on beans and broad beans, mealy aphids on cabbages. Each species has its preferences but all are formidable.
Prevention
Set up an insect net; pinch out the tips of broad beans once the first pods form, which limits blackfly (RHS); clean the greenhouse in autumn to stop them overwintering there; encourage beneficials (ladybirds, lacewings, hoverflies).
Early signs
Yellowing and twisted shoot tips, a blackish deposit of “soot” (sooty mould developing on the honeydew secreted by the aphids), ants climbing the stems.
Action / control
Crush small groups of aphids between thumb and finger. In case of a massive infestation, spray an insecticidal soap (black soap) at the dose on the label: it acts only on contact (UC IPM).
Sources
- RHS (Royal Horticultural Society) : Aphids (rhs.org.uk/biodiversity/aphids)
- RHS (Royal Horticultural Society) : Broad beans (rhs.org.uk/vegetables/broad-beans/grow-your-own)
- UC IPM (université de Californie), Pest Notes : Aphids (ipm.ucanr.edu)
Favourite plants / resources
Related plant entries
Tomato
Central plant of the tomato guild. The neighbouring basil is reputed to hinder aphids through its volatile compounds.
Bean
A nitrogen-fixing legume: in symbiosis with Rhizobium bacteria housed in its root nodules, it fixes nitrogen from the air, first for itself; part of it returns to the soil as its roots and haulm decompose, mainly benefiting the following crops. It belongs to the Three Sisters: maize serves as its stake and squash blankets the ground at its feet. Climbing varieties occupy the vertical layer while dwarf ones fill the low storey, two ways of inhabiting the bed. Its flowers feed bees and bumblebees, and at season's end, cutting the plants at the collar and leaving roots and haulm in place returns part of the nitrogen to the soil; the nitrogen in the seeds leaves with the harvest. Grown ahead of hungry vegetables, it readily opens a rotation.
Cabbage
A brassica with a long rotation: 4 to 5 years between two brassicas, 8 to 10 years after a clubroot attack (Réussir Fruits & Légumes, 2022), whose spores (Plasmodiophora brassicae) can contaminate the soil for up to 20 years (RHS). Very greedy (nitrogen, calcium, water). To be planted after a legume to benefit from the nitrogen.
Sweet pepper
A fruiting nightshade, hungry for both warmth and fertility: it calls for rich soil and a well-exposed bed among the summer crops. Basil, a classic companion to both tomato and pepper, is reputed to keep certain pests away through its aromatic compounds, while the French marigold, in a dedicated, dense planting, reduces soil nematodes (see its own entry) and draws in beneficial insects. Its flowers are visited by bees and by hoverflies, whose larvae devour aphids. Like any nightshade, it belongs in a rotation that avoids following tomato or potato, so as not to concentrate the family's shared soil diseases (verticillium wilt, for instance). Finally, it is kept away from fennel, reputed to hinder its neighbours.