Avoid the aphids

Two prominent pests of greenhouse peppers are the green peach aphid (Myzus persicae) and the melon aphid, sometimes called the cotton aphid (Aphis gossypii). Arm your staff with the knowledge of how to ID these pests and make sure you’re taking preventive measures to keep them at bay.

Green peach aphid

Description: This soft bodied, pear-shaped insect (bottom photo) is usually wingless and about 1/16 inch long. The wingless female is pale yellow-green. The winged migrant form has a yellowish green abdomen with a dark dorsal blotch. Both forms have a pair of tailpipe-like appendages known as cornicles. Nymphs are smaller than adults but similar in shape. They are pale yellow-green with three dark lines on the abdomen. All stages can be recognized by the shape of the frontal tubercles (on the front of the head at the antennal bases).

Life cycle: The green peach aphid has a complicated life cycle. It breeds continuously, and many generations are produced each year. The green peach aphid does not have a pupal stage; instead, each nymphal stage appears more like the adult. In the northern United States, green peach aphids overwinter as eggs, but in the Southeast, no eggs are laid. Female aphids give birth to young females during the growing season. High reproductive rates and resistance to pesticides make the green peach aphid a formidable pest in the greenhouse.

Damage: The green peach aphid has piercing sucking mouthparts, and feeds by inserting these mouthparts into plant tissue and sucking out the sap. Feeding interferes with proper nutrient transfer in the plant. This aphid can transmit more than 100 diseases, including cucumber mosaic virus on peppers. It also causes damage from the large amount of honeydew and subsequent sooty mold left behind.

Look for leaves that appear curled, distorted and discolored. Small to medium sized aphid populations are easily overlooked.

Melon/cotton aphid

Description: The cornicles on melon/cotton aphid are short (approximately 8.0 mm, the width of the body) and vary in color from light yellow to very dark green (making them appear black). The antennae are typically shorter than the body. Melon/cotton aphids do not have a distinct indentation at the base of the antennae like that of the green peach aphid.

Life cycle: The life cycle differs greatly between north and south. In the north, female nymphs hatch from eggs on the primary hosts in the spring. They may feed, mature and reproduce parthenogenetically on this host all summer, or they may produce winged females that disperse to secondary hosts and form new colonies. In the south, females continue to produce offspring without mating. It can complete its development and reproduce in as little as a week, so numerous generations are possible under suitable environmental conditions.

Damage: Melon aphids feed on the underside of leaves, or on growing tip of vines, sucking nutrients from the plant. The foliage may become chlorotic and die prematurely. Their feeding also causes a great deal of distortion and leaf curling. They also secrete a great deal of honeydew, which provides a substrate for growth of sooty mold.

Detection and monitoring

For both green peach and melon aphids, pay attention to sanitation for control. To prevent the introduction of new aphid species into the greenhouse, carefully inspect all new plants before placing them in the growing areas. Eliminating all weeds in or near the greenhouse can be useful since aphids may be lurking on the weeds and may enter the greenhouse or the crop. Winged aphids can easily move from the outdoors into greenhouses through open vents and establish on crop plants.

To detect aphids early, check several plants on each bench throughout the greenhouse weekly. Inspect the young growing tips, stems and buds of plants. Look for the presence of white cast (molted) skins, honeydew and black sooty mold fungi. Yellow sticky cards can capture winged aphids that have entered the greenhouse from outdoors, particularly during spring and early summer. Since most aphids are wingless, the use of yellow sticky cards is not a reliable indicator of the population levels of aphids within the greenhouse. Instead, you must conduct a direct visual inspection of the crop.

Sources: Penn State Extension; Oklahoma State University; University of Massachusetts Amherst; University of Florida