Richard L. Miller
Alan W. Smith
Winged Greenbug Adult, Wingless Greenbug, Greenbug Eggs
The greenbug, Schizaphis graminum Rondani, is an aphid or plant louse that has been recognized as a serious pest of oats, barley and wheat in this country since the 1880s. It is one of the most destructive insect pests of small grains in the Great Plains area. Its principle host plants are wheat and oats, but it also feeds on several kinds of grass and other grain crops.
For many years now, the greenbug has been known to feed on Kentucky bluegrass, but prior to 1970, it rarely caused damage. Since the mid-1970s, serious damage to bluegrass has been reported in several mid-western states. In the 1970s, a new strain developed which prefers feeding on bluegrass rather than grain crops and other grasses. It is a new biotype of the greenbug aphid. Areas of discolored grass, ranging from pale green to yellow to burnt orange, under shade trees or in sunny areas, may be caused by the feeding these small sucking insects.
Greenbugs feed by inserting their stylet-like mouthparts into the grass blades and sucking out the plant juices. While feeding, the aphids inject a toxic salivary secretion into the plant tissue which kills cells around the feeding area. Greenbug damage is often noted extending out from the base of shade tree trunks. The reason for this is not fully understood. Other shaded areas in the lawn are less damaged, and populations frequently develop in sunny locations.
When greenbug populations are small, symptoms appear as a barely detectable yellowing of the turf. When populations become larger over an extended period, the yellowing becomes much more noticeable, and the grass may even assume a rusty appearance. When this level of damage occurs, 30 or more aphids may be found on each blade of grass, and there can be several thousand per square foot. Continuous feeding can result in the death of infested turf.
As the grass is slowly killed, the aphids move as if in a wave from the dead turf area into living grass. They can always be found at the edge of dead areas, moving into healthy grass.
The greenbug has a typical aphid appearance but is smaller than many other aphid species. Its body is soft, somewhat pear-shaped and narrowed toward the front. When full grown, it is about 1/16 inch long. Winged and wingless females and their young are the forms most often seen. Color varies from pale yellow to pale green, with dark eyes. The legs are almost black and the antennae are long, darker than the body, and usually are held over the back of the body. A pair of short tube-like structures, sticking out from the tail end (cornicles), are tipped with black. Because of the seriousness of greenbugs as pests of small grains, its life cycle on those crops is well known. However, its life cycle on turfgrass is still being worked out.
As greenbug populations begin to build up in the South in early spring, the winged forms fly up and are carried northward on wind currents. It is these migrants that infest bluegrass lawns in the North each summer. It was once thought that the greenbug did not overwinter in the North. However, it isn't unusual for a greenbug population to show up in the same lawn for two or more consecutive years. The chance of such a reinfestation by windborn adults seems unlikely.
The females lay 1-10 eggs in the folds of grass blades. The eggs are pale and yellow when first laid, but become shiny black by the end of the third day. Eggs of the greenbug aphid have been found in Ohio lawns in the fall, and young in the following spring, thus the aphid is capable of surviving the winter as an egg in Ohio. During spring and summer, greenbug females produce offspring by giving birth to living young without fertilization. Under optimum developing conditions of about 75 degrees F, newborn greenbugs can be fully mature and give birth to living young themselves in 7-10 days. There are several generations per year and populations can build up very quickly under these conditions.
There a number of insects that prey on aphids. They include lady beetles, lacewings, bigeyed bugs, ground beetles, syrphid fly larvae, parasitic wasps and spiders. Heavy populations of these predators and parasites may well be the reason greenbugs are not serious pests in the spring. When greenbug populations explode, predators and parasites cannot suppress the population and are virtually ineffective in controlling this pest.
Chemical control is often needed where greenbug populations are causing noticeable damage to the turf. The recommended insecticide is acephate (Orthene). If the infestation is in only part of the lawn, spot treatments of only the infested area is recommended. Spot treatments should cover entire infested area plus a six-foot band surrounding the infestation. Rainfall during or immediately after a treatment will greatly reduce a spray's effectiveness. Under these conditions, examine the infested area and if greenbugs are seen 24 hours later, repeat the treatment. In addition, one should not mow for at least 24 hours after treatment. Granular formulations of insecticides are not effective in controlling greenbugs.
NOTE: Disclaimer - This publication may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registrations, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author and Ohio State University Extension assume no liability resulting from the use of these recommendations.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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