Aphids on leaf underside
Updated: May 17, 2021

Controlling aphids on vegetable plants

Appearance

  • Adults: Small, soft-bodied, tear-drop shaped, ranging in color from green to blue-green, yellow, orange, red, black, and grayish-white. 
  • Some are covered with fluffy white wax. Most have a pair of tubular cornicles near the tip of the abdomen (looks like a “dual-exhaust” system). Dispersing adults have wings.
  • Immatures: Resemble adults.

Aphid images

Life cycle/habits

  • Eggs laid in fall overwinter and hatch in spring. 
  • Many more generations are produced during the growing season. 
  • Aphids move slowly, congregating on new succulent growing tips and leaf undersides.
  • Winged dispersing adults may fly to other plants.
  • Aphids have long slender mouthparts to suck plant sap and excrete sticky honeydew. 
  • Aphids feed on plant leaves, stems or roots, depending on the species, and can transmit plant diseases.

Video contributed by Dr. Mike Raupp

Host plants 

  • A wide range including beans, beets, broccoli, Brussels sprouts, cabbage, cantaloupes, cauliflower, collards, cucumbers, eggplant, kale, peppers, potatoes, pumpkins, radishes, spinach, squash, tomatoes, turnips, watermelons.

Signs and symptoms 

  • Sucking of sap stunts plants. Leaves curl and/or discolor with white or yellow stippling.
  • Sooty mold may grow on honeydew, blackening leaves.
  • Aphids congregate on new growing tips but are also attracted to lush, overly fertilized growth or stressed plants.

Monitoring

  • Examine transplants to intercept infested plants.
  • Check leaf tips and undersides and along stems for clusters.
  • Inspect for sooty mold growing on honeydew. Note any curling, stunting, or stippling.
  • Ants frequently harvest honeydew from aphids, so the presence of ants may be a sign of aphid infestation.

Prevention/control

  • Do not plant infested transplants.
  • Aphids are mainly a problem May through June but have many natural enemies (e.g. ladybird beetles, lacewings, syrphid fly, parasitic wasps) that keep numbers controlled. Look for brown, swollen parasitized bodies.
  • Encourage predators with attractant plants and avoid toxic pesticides.
  • Control low aphid infestations with a robust spray of water.
  • If damage is obvious and predators and parasitoids few, use insecticidal soap. Check product label for directions before spraying. And avoid spraying when temperatures are above 85 degrees F.