Pests of greenhouse sweet bell peppers

The green peach aphid (Myzus persicae) is the most common aphid pest of greenhouse sweet peppers but there are other aphid species that can become a problem in greenhouse peppers. These other aphid species include: the melon aphid (Aphis gossypii), the potato aphid (Macrosiphum euphorbiae) and the foxglove aphid (Aulacorthum solani). Not all aphid biological control agents are equally effective on all aphid species so it is necessary to be sure of the identity of the aphid species in question. All of the species eventually develop winged forms.

Green peach aphids are usually light green in colour, but can be pinkish or yellowish in colour in the fall. The body is about 1.2 to 2.5 millimetres long and egg shaped. The winged forms can have black or brown coloured heads and black markings on the body.

Melon aphid

The melon aphid adults are usually either black or green when there are just a few aphids present, but as the population grows and the aphids become crowded the colours can range from olive green to yellowish green. Melon aphids are about the same size as green peach aphids: 1 to 3 millimetres long. They can be distinguished from the other aphid species by the dark black cornicles and short antennae.

Potato aphids

Potato aphids are quite large, 1.7 to 3.6 millimetres long, and the body is wedge-shaped and yellowish green to pink in colour. The head has prominent antennal tubercles that are directed outwards. Potato aphids will drop off the leaves when disturbed.

Foxglove aphids

Foxglove aphids are smaller than potato aphids but larger than melon and green peach aphids. This aphid is a shiny light yellowish green to dark green in colour with a pear-shaped body. The only markings on the bodies of wingless adults are darkish patches at the base of the cornicles.

Damage assessment

Aphids can be present in the pepper crop very early, even while the plants are just in the seedling stage. They can come in on the transplants as well. Aphids feed by sucking the plant sap. Symptoms of aphid infestation include the development of sticky honeydew on the leaves and fruit. The presence of honeydew on the fruit requires that the fruit be washed prior to going to market.

Sooty mold is often associated with the aphid honeydew; this mold uses the honeydew as a food source and grows to resemble a layer of ‘soot’ on the leaves and fruit. The presence of sooty mold on the fruit also makes washing the fruit a necessity. The growing points, young leaves, flowers and young leaves can be damaged and distorted. and in severe infestations flower abortion can occur.

Biological control

Aphid control should be started in propagation with the introduction of parasitic wasps:

• Aphidius matricariae for green peach aphid
• Aphidius colemani for the melon aphid and green peach aphid
• Aphidius ervi for potato aphid
• Aphelinus abdominalis for the potato and foxglove aphid

Parasitized aphids become silvery-brown in colour with a small exit hole at the back when the parasite has emerged. The larvae of the midge Aphidoletes aphidimyza feed on most aphid species, but will not feed on gall-forming aphids. Aphid hotspots and population explosions may require introductions of lady beetle species: Harmonia axyridis, the Asian lady beetle and large scale introductions of Hippodamia convergens.

Introductions of these predators and parasites may have to continue throughout the entire season. For best results, always use a combination of aphid predators and parasites. Consult your local supplier for information and recommendations on release rates.