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PLO-W sh,aWC 4� Biological Control of Aphids in the Greenhouse North Carolina has many different spe- cies of aphids, and life cycles and host plants vary among species. The green peach aphid is probably the worst pest for greenhouse growers because of its wide host range, broad distribution, ability to vector viral diseases, and difficulty of control. Aphids tend to be very communal and often congregate in groups on the tender parts of plants, preferring new growth shoots and tips and the undersides of leaves. Aphids penetrate plant cells and remove sap with their sharp, straw -like proboscis, The sap is used for energy and then excreted as a sugary, sticky fecal substance called hon- eydew. Black sooty mold fungus will often grow opportu- nistically on top of the honeydew. Other symptoms of aphid infestation include distorted new growth, yellow spots or mottling on upper leaf surfaces, curling leaves, and cast skins on leaves. The presence of ants in the greenhouse can also tip you off to an aphid problem. Ants love to feed on honeydew and will protect aphid colonies from predators and parasites so that they can harvest the sugary goo and take it back to their nest. Ants will even "herd" aphids from plant to plant! Ain't nature great? One of the main reasons aphids are such notorious pests is because populations have a tendency to explode. This is because aphids have the ability to reproduce sexually and asexually. Most aphids are females in the south. These fe- males do not have to mate in order to reproduce, and they often produce live young rather than eggs. Many genera- tions are produced each year. Adult green peach aphids pass the winter in North Carolina on greens and weeds (other species may overwinter in the egg stage). In a greenhouse, asexually reproducing aphids can be present year- round. Both winged and wingless forms may be present, Winged aphids often appear when the J communal living situation ITT becomes overcrowded — some aphids will develop wings so they can fly off in search of a new host plant. Detecting an aphid infestation early, or acting before they even show up, is the key to successful control. Early detec- tion requires proper scouting. Scouting should be performed at regular, timed intervals — once a week (twice a week in the summer), on the same day, at the same time, Record your observations so that you will be able to detect any pos- sible trends. Look especially carefully at plants prone to aphid problems, and at plant parts like the undersides of leaves, buds, or tender new growth. Watch for honeydew and cast aphid skins shed by the developing aphids as they molt through their juvenile stages. Avoid moving infested plants to new areas adjacent to susceptible plants. Flag loca- Page 2 tions where you find aphid populations so you can monitor them, There are several biological control options for greenhouse aphid pests, including green lacewings (Chrysoperla carnea, C. rufflabris, Chrysopa spp.), aphid midges (Aphidoletes aphidi- myza), parasitic wasps (Aphidius colemani and Aphidius matri- cariae), and lady beetles (Hippodamia convergens). The larval form of the green lacewing is a voracious t consumer of aphids and other soft- bodied pests such as scales, mealybugs, and whiteflies. Lacewing lar- vae, often called aphidlions, have flattened bodies that resemble tiny alligators. Eggs or larvae can be released, depending on how quickly control is needed. Adults are sometimes released into orchards to penetrate upper tree canopies, Lacewing larvae are slow to disperse but quick to find and consume prey after their release. The predaceous larvae of the mosquito - like aphid midge (Aphidoletes) are best used for controlling substantial popula- tions of aphids, The adult females lay their eggs in the middle of aphid colo- nies. The eggs hatch into orange larvae that kill aphids by injecting a toxin and then consuming them. If released into high infestations, Aphidoletes larvae tend to kill much more than they eat. This makes them capable of handling heavy pest pressure. Aphidius is a parasitic mini -wasp best used for preventing the establishment of aphids. These parasitoids can also tackle minor to medium infestations. If they become es- tablished they can provide protection throughout the season, except perhaps in late summer. The wasp lays its eggs in the abdomens of aphids. The larvae then hatches and consumes the aphid from the inside, eventually pupating inside the aphid "mummy ". Look for the telltale exit holes in aphid mummies to determine if Aphidius is doing its job. The convergent lady beetle is another vo- racious predator of aphids and other pests. Both larvae and adults are predaceous. ,Lgdy beetles are flighty, but if you water the site before releasing and release in the evening you will encourage them to stick around and earn their keep, Even when released properly, however, 90 -95% will Ely away (release rates should take this into account). But it's the 5- 10% that stick around that do the job. Synthetic food sources such as BiodietThl (a honeydew substitute) are available to help keep lady bee- 26