bean aphid

How to Identify and Control Bean Aphid

How to Identify and Control Bean Aphid

The bean aphid (Aphis fabae) is a small black insect in the genus Aphis, with a broad, soft body, a member of the order Hemiptera. Other common names include blackfly, bean aphid, and beet leaf aphid. It is a widely distributed pest of agricultural crops and can be controlled by chemical or biological means.

The bean aphid affects a wide range of garden plants, trees shrubs and certain vegetables (mainly beans and peas). It is often found in large numbers on the undersides of leaves as well as on soft new shoot tips or buds. As they feed, they secrete a sticky, honeydew substance which drips onto lower foliage and often becomes covered in a sticky black mould. This aphid also acts as a vector for viruses that cause plant disease.

The bean aphid has two forms: wingless and winged. The wingless forms are up to 2mm long and elliptical in shape. They are black in colour, although they can also appear dark green or purple. The winged forms are longer and more slender than wingless forms and have shiny black heads and thoraxes. The membranous wings of the winged forms are held angled over the body.

The bean aphid breeds profusely by live birth, but its numbers are kept in check, especially in the later part of the summer, by various predatory and parasitic insects. Ants feed on the honeydew it produces, and take active steps to remove the aphid’s enemies. Ants will often carry young aphids onto new plants to establish new colonies. In the autumn, winged forms move to different host plants, where both males and females are produced. These mate and the females lay eggs which overwinter .

How to Control Bean Aphid

There are several methods to control bean aphid infestations, both chemical and organic.

  • Chemical: Products containing pyrethrum, natural fatty acids or surfactant based products are all effective on bean aphid. It is important to read manufacturer’s instructions for use and the associated safety data information before applying chemical treatments.
  • Organic: Inspect plants regularly and deal with early symptoms immediately. Remove as many aphids as you can by hand or, if possible, cut off infested shoots and stems on susceptible shrubs. Spray the infested areas of a plant with a strong jet of water to keep aphid numbers down. Use nettings and fleeces to stop aphids spreading to susceptible plants. Encourage natural aphid predators such as ladybirds, Aphidoletes, hoverfly and lacewing larvae. These can be obtained from commercial suppliers and released on to affected plants outdoors. For greenhouse plants use parasitic wasps of aphids such as Aphidius matricariae and Aphidius ervi which can be purchased for release in a contained space.
  • Prevention: Regularly check plants for signs of aphid infestation and deal with them as soon as they appear. Encourage natural enemies. Avoid using broad spectrum insecticides which will kill beneficial insects as well as aphids. Encourage insectivorous birds by hanging feeders during the winter months and provide nesting boxes in the spring.

Bean aphid is a common and destructive pest that can cause significant damage to crops and ornamental plants. However, with proper identification and control methods, it can be managed effectively.

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