Aphids are sucking insects that feed on the sap within the food conducting tissues of the plant, reducing its vigor and causing distorted growth in severe cases. Aphid feeding is often accompanied by the presence of a black powdery mold growth on leaves (the so-called “sooty” mold), the mold growing on the sticky honeydew excreted by the aphids.
Aphid populations can build up to damaging levels in the absence of natural predators, and pesticide resistance is a common problem with this pest. Recommendations for minimizing aphid infestations include crop timing to avoid high population periods, proper planting to insure uniform stands, avoiding over-fertilizing with nitrogen, delaying use of insecticides until economic thresholds are met (to reduce liklihood of inducing pesticide resistance), and insuring good coverage (under leaves) of insecticide when plants are sprayed. Consult the Vegetable IPM Web Site for recommended controls of this pest.