Home lawns are commonly infested with insects and other pests which cause severe damage to turfgrass. These pests can be divided into two groups based on their location: SOIL INHABITANTS and THATCH INHABITANTS. Both groups severely damage lawns. A knowledge of pest biologies and habits is helpful when implementing effective control programs. If you are having trouble with a fungus or other plant disease go to our article on Plant Disease Products.
Damage to turfgrass from insect pests takes many forms. Feeding by soil-inhabitants such as white grubs, billbugs, and mole crickets usually shows up as wilted, dead or dying grass. Sod may be disturbed in areas where wildlife or pets dig up soil-inhabiting pests. Damage to turf by thatch inhabitants such as sod webworms, armyworms and cutworms is apparent when grass is cut off close to the ground. Damage by chinch bugs and spittlebugs, also thatch inhabitants, is similar to damage caused by soil inhabitants. Irregular spots of yellowish turf and dead spots may occur where chinch bug or spittlebug infestations go uncontrolled. Identifying your pest will save you time, money and your lawn.
Mole crickets are light brown, up to 1 1/2 inches long, have short, stout forelegs, spade-like feet, and large eyes. The young resemble the adults except that they are much smaller, have no wings and are sexually immature. Adults lay eggs in underground cells in the spring. The eggs hatch in 2 to 4 weeks, depending on the weather. Nymphs feed and grow through the summer, and mature into adults in the fall. Mole crickets spend the winter deep in the soil but come to the surface to feed during warm periods. Adult crickets leave the soil on warm spring nights to fly around, sometimes in huge numbers, looking for mates and egg-laying sites. There is one generation per year, and most adults die by early summer. Two generations per year have been reported in isolated coastal areas. The most damaging species of mole crickets feed on grass beneath the soil's surface. Both young and adults burrow beneath the soil and make small tunnels. Mole crickets will build up in an area and completely destroy the grass, leaving bare ground if left untreated. Click here for mole cricket control in lawns.
These turf destroying grubs are plump, C-shaped insects with three pairs of legs. They are whitish with dark areas near the rear. They have a distinct, brown head. The adults are beetles commonly referred to as chafers, May beetles or June beetles. Adult female beetles lay their eggs in the soil. The grubs hatch and spend most of their life beneath the soil feeding on underground plant parts. Most have rather long life cycles with the grub stages lasting from several months to two or three years. Grub feeding destroys the roots, leaving the tops to wither and die. In heavy infestations, roots are pruned off to the extent that turf can be rolled back like a carpet.
Fall is the best time to inspect for grubs, although early spring can also bring on early infestations. At these times the grubs are near the soil surface feeding at the root zone. Use a spade to cut three sides of a strip one foot square and three inches deep. Force the spade under the sod and lay it back, using the uncut side as a hinge. Use a trowel to dislodge soil from the exposed roots. After inspection, replace the strip of sod to insure roots can re-establish contact with the soil. Repeat this procedure in several other areas of the lawn to locate possible white grub infestations.
Adult billbugs are weevils 1/5 to 3/4 inch long. The reddish-brown to black adults have a pair of jaws at the tip of a long snout which resembles a bill. The young are white, legless grubs about 3/8 inch in length with the rear end wider than the head. Adults feed above ground and deposit eggs in the stems of host grasses. Hatching larvae feed within the stems; larger larvae feed on the crown; mature larvae feed on the roots of the turf. Zoysiagrass and Bermudagrass are most often injured, but, feeding may occur on many grasses. In heavy infestations, roots of grass are destroyed and the turf killed in irregular patches. Damage from billbugs differs from white grub or mole cricket injured turf as infested soil usually stays firm.
Spittlebug adults are about 3/8 inch long, dark brown or black, and have two orange stripes across their wings. The nymph is ivory-colored with a brown head. They live inside masses of spittle or froth, hence the name "spittlebug." Orange-colored eggs are deposited in bits of hollow stems and other debris. Nymphs hatch in about two weeks and begin to feed immediately by sucking juices from the grass. They cover themselves with a frothy mass known as spittle. There may be one or several nymphs in each spittle mass. The masses are found from just below the soil surface to a few inches above it. A heavily infested area will feel "squishy" when you walk across it due to numerous spittle masses. Centipede grass is especially prone to spittlebug infestation and populations often begin and increase in shady areas. In the Southeast United States there are 2 to 4 generations of spittlebugs each year. Control of spittlebugs is best achieved by treating with Acephate 75 Turf during the early morning hours, preferable just before dawn. Treatment is similar to treating for molecrickets with Acephate 75 Turf.
Chinch bugs are most damaging to St. Augustine grass. You may see them on grasses such as zoysia, Bermuda, and centipede, but infestations usually occur where high populations have built up on St. Augustine grass. Adult chinch bugs are about one-fifth of an inch long and black with white wings folded over their backs. The insect mates early in the season when the temperature reaches 70 degrees Fahrenheit. The female lays eggs on roots, stems, leaves, leaf sheaths or crevices in nodes and other protected places. Eggs are laid over a 2 to 3 week period, with one female laying as many as 500 eggs.
The young chinch bugs ( called nymphs) develop into adults in four to six weeks. Nymphs are yellow upon hatching but soon turn red and have a light colored band across their abdomens. With each molt, nymphs more closely resemble the adults. There are 2 to 4 generations per year. The chinch bugs insert their slender beak into the grass and suck the plant juices. As the chinch bug sucks the plant juices, it releases a toxin that causes yellowish to brownish patches in turf. Typical injury appears as spreading patches of brown, dead grass. This pest is a sunshine-loving insect and seldom attacks grass in a dense shady area. Discolored areas caused by chinch bug feeding that are in open sunlight several hours daily may be "hot spots" for chinch bug damage. Most homeowners will first notice dead patches of grass along a driveway, curb, sidewalk or foundation of the home, due to the heat emitted from such objects. Because they can fly, it is difficult to keep an area free of chinch bugs if they are emerging from neighboring lawns, golf courses or nearby croplands. Click here for Chinch Bug Control.
Sod webworms are caterpillars of small brown to dull gray moths. Webworms grow to a length of nearly 3/4 inch and vary in color from pinkish white to yellowish brown with a light to dark brown or black head. They are covered with fine hairs. The moths have a wingspan of about 3/4 inch. They fold their wings closely about their bodies when at rest and have a prominent forward projection on the head. Moths hide in shrubbery or other sheltered spots during the day. They fly over the grass in early evening. The female scatters eggs over the lawns as she flies.
Sod webworms feed only at night. Damaged grass blades appear notched on sides and are chewed raggedly. Irregular brown spots are the first signs of damage. Large areas of grass may be damaged severely. A heavy infestation can destroy a lawn in only a few days. Insecticide application should be timed for treatment during early evening hours when caterpillars begin feeding on the surface of the turf.
Identification: Armyworms, which attain a length of 1/2 inches, are also caterpillars of moths. Their bodies are greenish when small but become brown when fully grown. Several stripes are usually apparent, extending from the head to the rear. The adult is a mottled brownish-gray moth with a wingspan of nearly l l/2 inches.
Life Cycle and Diagnosis: Moths lay clusters of eggs on grass blades, lawn furniture, white or light colored walls and other objects near lawns. Caterpillars hatch and begin to feed on the turf. Damaged turf appears ragged with individual blades showing signs of chewing damage. When numerous, they may devour the grass down to the ground. Caterpillars pupate in the soil. The moths emerge within a couple of weeks. They are active mainly at night. There are three to six generations a year. As with sod webworms, time insecticide applications to control armyworms during the early evening when caterpillars are feeding on the surface of the turf.
Identification: Cutworms, also the caterpillar stages of certain moths, grow to a length of 1 1/2 - 2 inches. They are mottled dull brown, gray or nearly black and usually appear plump and greasy. If disturbed, the caterpillar usually curls into a C-shaped ball. The front wings of the moth are dark brown to gray, are mottled or streaked, and have a wingspan of 1 1/2 - 2 inches.
Life Cycle and Diagnosis: Eggs are laid on grass and weed stems or behind the leaf sheath of such plants. Caterpillars usually remain below the ground surface, under clods, or other shelters during the day and feed at night. Foliage or stems may be cut off (hence the name cutworm) by the caterpillars. Cutworms pupate in the soil. There may be several generations in a year. Due to their nocturnal behavior, it is best to time control measures for early evening when caterpillars are present on the surface of the turf.
Most insect pests of turf can be controlled when damaging populations are found. However, remember the first step to management of lawn pests is prevention. Good cultural practices are essential to prevent insect pests from destroying turf. Use recommended methods of fertilization, watering, mowing, etc., to keep grass healthy and growing vigorously. A healthy lawn can tolerate light insect infestation and damage is masked or overcome by rapid growth of plants. Thatch removal is one means of preventing chinch bug and spittlebug outbreaks. Heavy thatch accumulation provides an ideal environment for these insects. Thatch also interferes with delivery of insecticides to the insects.
Proper Selection of Control Materials
Insecticides labeled for insect control on home lawns are available in several formulations: emulsifiable concentrates, wettable powders, soluble powders, and granules. The formulation selected, as well as the specific insecticide chosen, determine the level of control. For example, spray applications of insecticides provide the highest degree of control within the first 24 - 48 hours after application. In general, the initial control with granular treatments is less than that from sprays. Insecticidal activity begins only when the granule absorbs moisture and releases the insecticide.
Correct Application Methods
Application methods are extremely important in turf insect control. The homeowner may use the most effective insecticide available, but if the method of application is poor, the level of insect control will be disappointing. The volume of spray applied should be adequate for uniform coverage of leaves, stems and thatch, where the target pest lives and eats.. Too little volume will result in poor coverage and ineffective control. In general, a minimum of 1-3 gallons of finished spray per 1000 sq. ft. is required for adequate coverage.
To control insect pests living in the soil, the target zone for the insecticide should be the soil at the root zone. Liquid and granular formulations must be watered in sufficiently to move insecticide off the surface, through thatch, and to the root zone. In lawns with heavy thatch it is of benefit to de-thatch the lawn prior to insecticide application. To control surface feeding pests, the target zone for the insecticide should be the leaves, stem and thatch. Spray formulations leave residues that remain on the surface and provide control of thatch inhabitants.
Water and Irrigation Requirements for Pesticide Applications
Timely use of irrigation can help get best results with insecticides for soil-inhabiting pests. During dry weather the turf should be irrigated prior to treatment. This will help the insecticide to penetrate grass blades and dry thatch. Follow label directions in regard to irrigation procedures following application.
Granular insecticides should be applied to dry turf. Granules often stick to wet grass blades and do not penetrate the thatch layer and reach the soil where they belong. Rapid watering-in is desirable with granular formulation, but it is not as critical as with liquid materials. At least one-half inch of water should be applied to activate granular materials to place them in contact with pests located at the surface. An additional half-inch to one inch of irrigation following treatment will carry the insecticide down through thatch and into the soil to the root zone. Delays in watering-in control materials will greatly reduce the chances of good control due to insecticides being broken down by direct exposure to sunlight. This is particularly true of the organophosphate class of insecticides. Common organophosphates include Diazinon, Dursban, Malathion, Acephate and Oftanol.
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