Plants are often disfigured and damaged by several species of small flies that live as maggots between the upper and lower surfaces of the leaves. Their feeding causes large white blotches and winding trails through the interior of the leaf. Infected leaves are unattractive and unfit for human consumption. The preferred hosts of the spinach leafminer are spinach, beet, and chard. The insect also attacks many species of weeds. Adult flies emerge in April and deposit eggs on the underside of the host plant's leaves. The eggs hatch in four to six days, and the young maggots bore directly into the leaves where they feed for 10 to 14 days. There are three generations each year.
Eliminating weeds will aid in the control of leafminers. During most years sprays are needed to prevent injury. Consult the most recent Commercial Vegetable Production Guide (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.
Aphids are small, soft-bodied insects, often called plant lice. They spread several virus diseases, reduce vigor and yield of plants, and contaminate leaves. Sometimes natural controls, such as beneficial parasites, hold down aphid population, especially if you have not recently used a broad-spectrum pesticide.
Eliminating weeds will aid in the control of aphids. Consult the most recent Commercial Vegetable Production Guide for specific control measures. Follow directions on the labels according to plant type when applying insecticides.
Two worms attack leafy vegetables: the cabbage looper and the imported cabbage worm. The tiny, light green worms are called loopers because of their characteristic way of walking. The looping movement results from having only two pairs of legs toward the tail end of the body. Loopers do not overwinter in Pennsylvania, so problems vary from year to year. However, it is during late August and September that the looper can cause considerable injury. The imported cabbage worm is velvety green with numerous ridges across the body. The worms have four pairs of legs on the center of the body. The cabbage worm is a persistent problem, from early spring until frost. The adult insect is the common white butterfly often seen flying around cabbage plants.
Avoid spraying directly over the tops of plants since most eggs and young loopers feed on the underside of leaves. Pest control programs for home garden vegetables use both cultural and chemical control measures. The success or failure of a fungicide or insecticide is related to correctly identifying the pest problem, the method of application, weather conditions, correct timing of sprays, and choosing the right pesticide. Consult the most recent Commercial Vegetable Production Guide for specific control measures. Follow directions on the labels according to plant type when applying insecticides.
Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.
Authored by: Shelby Fleischer