Over the years, many growers have asked me about the use of beneficial insects in potato production. One of the key pest targets are aphids, especially the green peach aphid. The green peach aphid is devastating because it carries the potato leaf roll virus that seriously affects seed production and the quality of potatoes used for processing into French fries (pommes frites) and potato chips (crisps). More on the green peach aphid and viral vectoring in later columns.
Are lacewings affective in controlling aphids? Are they commercially available? Are commercially sources reliable?
From left: Adult lacewing, eggs, new larvae (aphidions)
Using predatory insects may aid delaying insecticide application and lessen the number of needed treatments. Other advantages of predatory insects, both natural and released populations, are lowering the risk of chemical resistance by pests and suppression of secondary pests.
The performance of natural populations of predatory insects has been somewhat documented and varies with different situations. For instance, beneficial insects work well in perennials such as alfalfa but less well in semi-annuals such as potato. The major drawback is their lag time to respond to rapidly growing prey (pest) populations. The crop may have been economically damaged before the predator insects build up sufficiently to reduce the pest population.
Common Green Lacewing (Chrysoperla carnea) is readily available commercially both in the USA and Canada, and is considered the best for row crops and in drier areas than the green lacewing (C. rufilabris) that is also available. The common green lacewing specializes in feeding on aphids. Adults are reared in insectaries and eggs are sold mixed with a carrier. The eggs should be dispersed as soon as they arrive since the larvae are cannibalistic. Don't release them near ants since they will eat the eggs. The main problem with using these predators has been the method of dispersal on a large scale. Recently, however, a successful method was developed called the BioSprayer used with an adhesive, BioCarrier. The BioSprayer can be mounted to a vehicle and BioCarrier is used to adhere the eggs to potato leaf surfaces.
Life Cycle -- Green lacewings are found naturally in Nebraska and I've observed them in potato fields. Lacewing larvae eat CPB, GPA and potato psyllid; adults feed on nectar, pollen and aphid honeydew. They disperse through the field as adults. Pupae overwinter and an adult emerges in late March and early April. Eggs are laid in April and larvae emerge around the end of the month. The larvae change to adults after a couple of weeks. The life cycle is about one month. There are two to four generations produced during the growing season. The larvae are voracious predators.
Appearance -- Adults are colored light or pale green and golden eyes. The wings are lacy -- large, clear, membranous with green veins and margins and are held over the length of the body, about ¾ inch long. Antennae are long and hair-like. They are attracted to and feed on aphid honeydew, laying eggs nearby or near other prey. The eggs are white and each is held at the end of a hair-like stalk attached to the leaf. Larvae, called aphid lions, are able to eat up to 600 aphids each). They look like tiny alligators and are creamy colored, mottled with brownish red markings; they are about ¼ inch long. They have well-developed legs and large pincers with which to suck out bodily fluids from prey. The larvae spin out a cocoon (pupa) on the underside of leaves.
Pesticide Tolerance -- Lacewings may have tolerance for many insecticides. In the lab, tolerance developed to pyrethroids (Ambush, Pounce, etc.), organophosphates (Guthion, Imidan, Monitor, etc.) and carbaryl (Sevin).