University of Manitoba - Faculty of Agricultural & Food Sciences - Aphids

Problem type: Insect

Name of problem: Aphids

Plant name(s): All plants

Symptoms / Characteristics:
Aphids may be green, yellow, brown, red or black, depending on the species and host plant. They usually colonize on the underside of leaves on newer terminal growth. Aphids deposit "honeydew" (clear sticky substance) that leaves plants and other objects nearby sticky to touch. A black sooty mold may develop where honeydew has been deposited, turning leaves and branches black. Honeydew drops may also attract other insects, especially ants that will feed on the sweet substance. Heavy infestations of aphids may cause leaves to yellow, wilt, pucker or become severely distorted due to sap removal and saliva injection. Affected flower buds and fruit may be deformed. Aphids molt their skins a few times as they mature leaving behind white skin sheds.

Adult aphids are winged insects that fly to host plants to deposit their young. Usually the young are deposited on younger plant parts or flower buds. The immature aphids are wingless and begin to feed on leaves and stems by sucking the plant sap with their piercing sucking mouthparts. Aphids are small pear shaped insects with long legs and antennae, usually colonizing on leaf undersides. Immature aphids mature in 1 to 2 weeks and can then produce new young. Each aphid is capable of producing 40 to 60 offspring up to several times. This can result in high populations on a plant in only a few weeks. When plants become overcrowded, winged adults will fly to search for a new host.

Control / Preventions:
There are many natural predators of aphids, such as lady bugs and parasitic wasps. Other means of control may not be needed if these predators are present. Inspection of plants regularly is needed to catch aphids early. Check surrounding plants that may host aphid populations. Thistles and other weeds may serve as hosts. Many vegetables are susceptible to aphid damage. Covering seedlings until they are more mature will help prevent infestations. Picking or pruning off smaller infested plant parts may be all that is needed. A high pressure water spray can knock aphids off as well as remove the sticky honeydew. Horticultural soaps and oils can be sprayed thoroughly on plants. Ensure leaf undersides are covered thoroughly. Curled leaves may serve as protection against sprays. Do not use soaps or oils on water stressed plants. Repeat applications may be needed. Other insecticides are available for aphid control. Make sure to read all labels carefully for proper application and appropriate plants targeted.

Generally, healthy and established plants can withstand heavy aphid infestations. Stunted growth and decline may result after long or repeated infestations.