Hornworm caterpillars of the whitelined sphinx, feed on leaves of apple, azalea, chickweed, elm, evening primrose, portulaca, purslane, Virginia creeper and many other plants. Caterpillars grow up to 3 1/8 inch long, have yellowish-orange heads and their bodies are generally green with two black stripes along their sides. A black form with yellow stripes also occurs. Adult moths have a wingspread of about 3 inches, with long narrow brown and black forewings marked with white veins, borders and a broad white and stripe running across the middle. Hind wings are dark brown with a rosy-white band across the middle, and the moth’s body is brown with white stripes on the head and thorax, and bands of black and white spots on the abdomen. These moths fly in daylight and evening hours, with hovering flight resembling that of humming birds as they sip nectar from flowers. This is one of the most commonly observed sphinx or hawk moth species.
Winter is spent in the pupal stage, which appears brown and spindle-shaped, 2 to 3 inches deep in the soil. Adult moths emerge in the spring and mate. Female sphinx moths lay clusters of up to 1,000 white eggs, usually in April or early May. Tiny caterpillars hatch from these eggs in about 10 to 14 days. Caterpillars molt several times during development before they crawl down the tree trunk and pupate in the soil. Adults emerge several days later. There may be 4 to 5 generations per year.
High numbers of caterpillars can defoliate ornamental trees or shrubs.
Generally insecticides are not needed for control of White-lined Sphinx larvae because their feeding is usually confined to weeds. Keep in mind that the moth is beneficial for weed control and pollination when considering control. However, if they should attack valuable plants such as roses, small numbers can be hand picked and destroyed but if they are too numerous to control by hand, a wide range of insecticides will provide effective control. When using an insecticide make sure it is labeled for the intended use and read and follow label directions.