Insect I.D.: May 2001, A Threat To Turf: Leaf And Stem-Inhabiting Pests

Most of these pests have piercing-sucking or rasping (mites) mouth-parts that pierce the plant and withdraw plant liquids as food. While this alone causes plant stress (yellowing and loss of turgidity), the primary cause of plant death from such pests is that the feeding process includes injection of salivary fluids into the host plant. By various means, including plugging vessels that translocate water and nutrients, these substances can cause the plant to die. The greenbug aphid, mealybugs and twolined spittlebug are included in this group.

CLOVER MITE. This pest attacks a wide variety of plants, including Kentucky bluegrass, ryegrass and clover.

Only females are known. Adults are reddish- to chestnut-brown, 0.016-inch (0.4mm) long, and have the front legs about twice the length of the other legs.

Like other mites, the clover mite probes the surface of grass blades giving a silvery appearance to the upper surface. Populations of four to five thousand mites per square foot are common. Sun and wind further desiccates host plants. Damage is similar to and may be misdiagnosed as winter desiccation caused by wind. Damage occurs on home lawns, usually next to buildings.

WINTER GRAIN MITE. The winter grain mite is a pest of grains west of the Mississippi but is widely distributed throughout North America. Grasses, including Kentucky bluegrass, fine fescues and perennial ryegrass, are also hosts but damage to legumes, vegetables and other plants has been reported.

The adults are relatively large for mites, up to 3/64-inch (1 mm) long. They are the only turf-inhabiting mites with olive-black bodies, bright red-orange legs and mouthparts, a pair of white eye spots, and a dorsal anus. Only females are found.

During warm sunny winter days, this mite can be found on the crowns of grass plants, in thatch and at the soil surface. On overcast days and at dusk, the mites often "appear" in great numbers on the grass leaves. The dorsal anus, surrounded by a red-orange spot distinguishes this mite from all others one might find in cool-season grasses. While the mite is visible to the naked eye, a 10X hand lens is needed to see the dorsal anus.

BERMUDAGRASS SCALE. In the United States, bermudagrass scale attacks bermudagrass from California to Florida and is known in Hawaii.

This scale is most frequently reported on bermudagrass, though it has been found on centipedegrass, bahiagrass, St. Augustinegrass and tall fescue.

Bermudagrass first appears to grow slowly, turn yellow in color, often resembling drought stress. Heavy infestations may dramatically thin and kiss patches of bermudagrass. This type of damage is more evident during periods of hot, dry weather. Where bermudagrass enters a winter dormancy, this scale can cause delay in spring green up.

RHODESGRASS SCALE. Rhodesgrass mealybug occurs from South Carolina to southern California. This species attacks over 70 species of grasses, including rhodesgrass, St. Augustinegrass and bermudagrass wherever it is grown.

Only asexually reproducing females are known. The adult body is also saclike, broadly oval, dark purplish-brown and 1/16- to 1/8-inch (1.5 to 3mm) long. The fluffy waxy covering turns yellow with age. The dark female body is exposed through openings at both ends of the waxy cover. A very long, 1/8- to 3/8-inch anal filament excretes a sweet liquid (honeydew. Though this pest is actually a mealybug, it is immobile, like a scale insect, once settled.

GREENBUG. This greenbug (an aphid) is reported to have damaged turfgrass from Kansas to New York, south into Kentucky and Maryland, and has also been found in California.

Over 60 members of the grass family are hosts. Host turfgrasses include Kentucky bluegrass, Canada bluegrass, annual bluegrass, fescues and perennial ryegrass. This aphid is known to reproduce on Kentucky bluegrass, chewings fescue and tall fescue.

Young aphids look like adults except smaller. Their pear-shaped body is light green and usually has a darker green stripe down the back. The tips of the legs, antennae and cornicles (pipe-like structures on the upper side of the abdomen) are black. Nymphs destined to become winged forms have obvious wing pads in the last instar.

Adults are about 5/64 inch (2mm) long and have the same green color and black markings as the nymphs. Winged forms usually appear when overpopulation occurs, often after considerable turf damage has occurred. Winged adults are usually darker green and have wing veins marked with black.

Greenbug damage is commonly found as circular yellowed areas under trees, but also occurs in open areas as well. There is only speculation about why the damage occurs under trees, but what is known is that this aphid does not (can not) feed on trees. Close (hand and knees) examination of turf in and around areas showing typical symptoms is necessary, since the aphids are not readily seen from a distance.

Young and mature greenbugs suck plant fluids from their grass host and simultaneously inject salivary fluids into the plant. This fluid causes the tissue around the point of injection to turn yellow, then orange. Individual grass blades may have 50 aphids on them. In heavy infestations, the turf turns to a distinct burnt-orange color (especially visible after rain or irrigation), and soon, the complete plant dies. Greenbug discoloration is often confused with the similar discoloration caused by turf rust disease. Greenbug infestations and damage can occur from June to November.