General Turf Insects – Identification, Biology & Principles of Control

General Turf Insects – Identification, Biology & Principles of Control David J. Shetlar, Ph.D. The “BugDoc” The Ohio State University, OARDC & OSU Extension Columbus, OH © November, 2003, D.J. Shetlar, all rights reserved

White Grubs Mole Crickets Caterpillars (Cutworms, Armyworms, & Sod webworms) Billbugs Chinch Bugs Nuisance Pests Major Turfgrass Insect Pests

Notes: The major turfgrass insect pests are found around the world. Each continent has its own species that are unique and many turfgrass pests have been introduced through commerce. White grubs, mole crickets, caterpillars, weevils (billbugs, stem weevils), sucking pests (chinch bugs, aphids, scales), and mites are found wherever turf is cultivated. Pests that destroy turf roots and crowns are the most lethal. White grubs, mole crickets and weevils are the most significant pests in this group. Pests that eat foliage (e.g., caterpillars, crane fly larvae) or remove foliage cell contents (e.g., aphids, mites) rarely kill turf, but can cause severe discoloration, stunting, thinning and general aesthetic problems. Pests that suck juices from turfgrass plants often clog vascular bundles (e.g., chinch bugs) which can kill stems and leaves. If this activity is performed at the crown level, entire plants can be killed. Most of these sucking pests cause discoloration and stunting of turf growth, but they are rarely lethal unless excessive populations are built up. Nuisance pests are generally defined as organisms that rarely kill turf and are usually annoying or inconvenient to people near turf or trying to utilize the turf. Ants, ground nesting wasps, clover mites and similar organisms are included in this group.

Turfgrass Insect Pests by Target Zone (the Target Principle) • Soil-inhabiting • Leaf and Stem-inhabiting • Stem and Thatch-inhabiting • Nuisance

Notes: Insect and mite pests of turfgrass are often discussed according to taxonomic classifications (e.g., bugs, beetles, caterpillars, etc.), but they are usually discussed according to the turfgrass zones they inhabit – leaves & stems, stems and thatch, roots and soil. It is appropriate to discuss pests in this manner because this approach tends to force you to think about the zones that these pests generally occupy. This becomes most important when you consider implementing controls. If you are using pesticides, biological controls or cultural techniques, they will not work if they don’t reach, inhabit or act in the zone where the pests are found. As an example, knowing that cutworms eat turfgrass foliage, watering in a pesticide application into the soil reduces the chances that the cutworms will ingest foliage that contains the toxic residues. On the other hand, white grubs will not contact a pesticide left on turfgrass leaves. The material must be moved off of the leaves and stems, through the thatch and into the thatch-soil interface where the grubs are feeding. The Target Principle refers to the thinking of pests occupying specific zones in the turfgrass profile. If you don’t target your controls to the zone being occupied by the pest, our efforts will be wasted.

Leaf & Stem Pests Chewing Pests Sod Webworms Cutworms Armyworms Skippers Sucking Pests Bermudagrass Mite Clover Mite Winter Grain Mite Banks Grass Mite Greenbug (aphids)

Notes: In general, turf-infesting caterpillars are the major insect pests that actually eat turf foliage. While there are also some weevil adults and the larvae of crane flies that may feed on turf foliage, these are usually discussed under stem and thatch pests because this is the zone that the larvae generally occupy. Likewise, most turf caterpillars actually hide or build burrows into the thatch or soil zones, emerging periodically (usually at night), to eat turfgrass leaves. A few turf caterpillars feed on turf foliage when young, but concentrate on stems when they are larger. The cranberry girdler and bronzed cutworms are examples of caterpillars with this habit. The guild of pests that have sucking mouthparts, yet feed on leaves mainly include aphids and mites. Several aphids (mainly the greenbug and Russian oat aphids) feed on turf leaves, while others feed on the stems or even below ground, on the roots. Some mites (e.g., clover and winter grain mites) feed on leaf surfaces, but they spend the day hiding in the thatch. Other mites remain on grass foliage all the time (e.g., zoysiagrass and Banks grass mites). Still others feed on the grass stems, under the leaf sheaths and this activity causes stunting of the stems and foliage (e.g., bermudagrass and buffalograss mites).

Sod Webworms True Sod Webworms [Crambinae] Bluegrass WW P. teterrella Larger SWW Pediasia trisecta Western SWW Tehama bonifatella Striped SWW Fissicrambus mutabilis Corn Root Webworm Crambus caliginosellus Vagabond Crambus Agriphila vulgivagella Tropical Sod Webworms [Pyralinae] Tropical SWW Herpetogramma phaeopteralis

Notes: All the sod webworms are in one family of moths, the Pyralidae. This family generally contains medium to small moths that usually have a triangular outline when at rest. However, one subfamily, the Crambinae, has adults characterized by having pronounced labial palps which project like a snout in front of the head, and the adults generally roll the wings around the body which gives them a cylindrical shape when at rest. The Crambinae are often called the crambid sod webworms or true sod webworms. The true sod webworms use their body form to hide in grasses. When at rest, the adults generally orient themselves head down with the wings and body held out at an approximate 30 to 40 degree angle from the grass stem. This causes them to look like a dead, rolled up leaf. The tropical sod webworms are in the family Pyralinae and the adults don’t have enlarged, projecting labial palps nor do they roll their wings. Pyralid caterpillars usually have light colored or translucent cuticle with rows of distinct scleritized plates on each segment. These plates are often dark colored, giving the appearance of having rows of spots. Most sod webworm larvae are less than one inch long, usually being ½ to ¾-inch long when mature. While many crambid webworms survive in cool-season zones, the tropical sod webworms can not survive freezing temperatures.

Adult bluegrass webworm Larva and frass Sod Webworms Spring damage

Notes: Sod webworm damage is rarely evident in high cut turf (lawns, sport fields, golf course roughs and fairways). It occasionally appears as the disease, dollar spot, in the spring when overwintered sod webworm larvae sever stems rather than feeding on the foliage. During times of summer dormancy, sod webworms can thin out the remaining green stems and leaves, but they are not known for killing such turf. If sod webworms are present and the turf died, the death was more likely due to billbug damage, disease or prolonged drought. If sod webworms are suspected in high cut turf, spread the turf canopy and look for the characteristic fecal pellets – frass. If the frass is straw colored, it is old. If green, it is recent and the sod webworms are probably still active. Sod webworm adults usually take flight when disturbed by mowing or walking across the turf. However, the mere presence of adults does not mean that there is a sod webworm problem. In field evaluations, sod webworm damage is rarely evident, especially in high cut turf, unless the larval populations exceed 50 nearly mature larvae per square yard of turf.

Striped sod webworm adult Larger sod webworm adult Vagabond sod webworm adult Western sod webworm adult

Bluegrass webworm Larger sod webworm Striped sod webworm Cranberry girdler Sod Webworm Distribution Maps

Sod webworm damage to green often resembles disease or other maladies.

Sod webworm silk and topdressing cover over burrow, on golf green Sod webworm larva in burrow on sand-based green.

Notes: On the short cut turf of golf course greens, sod webworm damage appears as irregular lines or trails. In the spring, the overwintered larvae often make crescent-shaped trails that consist of silk lined burrows, constructed just below the mow line, that contain top dressing and grass clippings on the surface. Within the protection of these burrows, the caterpillars extend their burrows by eating the turf down. On one end of these surface burrows, the caterpillars extend their burrows into the thatch and underlying soil. The larvae appear to hide in these deeper burrows during the day. While these silk lined burrows rarely interfere with ball roll, birds often peck at the different colored areas and they may pull up tufts in their attempts to extract hiding webworms.

Bluegrass Webworm in Ohio

Tropical Sod Webworm Larva and frass in St. Augustinegrass Adults lack the elongate palps of regular sod webworms, and they hold the wings flat, in a triangular shape.

Tropical sod webworm damage to a bermudagrass green often looks like disease or irregular trails. Upon close inspection, silken tunnels covered with topdressing are found.

Cutworms & Armyworms (Noctuidae) Cutworms Black Cutworm Agrotis ipsilon Bronzed Cutworm Nephelodes minians Variegated Cutworm Peridroma saucia Armyworms Common Armyworm Pseudaletia unipuncta Fall Armyworm Spodoptera frugiperda Yellowstriped Armyworm S. ornithogalli

Notes: Cutworms and armyworms are generally robust caterpillars that are commonly one to 1.25-inches long when mature. The adults are medium-sized moths that fold their wings flat over the body (cutworms) or hold them roof-like (pitched) over the body (armyworms). The black cutworm is the most commonly encountered pest, especially on golf courses. This pest can not withstand freezing temperatures (where the soil may freeze to 25ºF or below), but reinvades northern areas from the Gulf States each season. The bronze cutworm is a cool-season pest, having larvae feeding in the fall, under the cover of snow and into the spring. It is not common, but does have periodic outbreaks, especially in lawn turf. The variegated cutworm is often declared to be a common turf pest, but I have found it to be relatively uncommon in turf. There are several other cutworm species that may be occasionally found in turf, especially turf with broadleaf weeds. The armyworms include two main groups: the “common” armyworm (actually the common name is just: armyworm) and the Spodoptera species (includes fall, yellowstriped, and beet armyworms as well as the corn earworm). The common armyworm can survive freezing temperatures, but the Spodoptera species are semi-tropical and not capable of surviving freezing temperatures. All armyworms have conspicuous stripes on the body and when present in large numbers, they can “march” across the turf eating everything green down to the thatch.

Black Cutworm Distribution Map The black cutworm can only overwinter in southern states (dark shading), and it normally flies northward with spring storm fronts. It may have four to five generations in the transition zones (medium shading) and two to three generations in the cooler-transition zones and true cool-season zones (light shading).

Black cutworm damage spots on short-cut bentgrass. Black cutworm larva feeding at night. Black cutworm larvae the morning after treatment with insecticide.

Black cutworms usually appear to have a broad, light colored striped down the back and a pebble-surfaced integument. Black cutworm females attach eggs to grass blade tips. Black cutworm adults feed on nectar at night and then locate turf on which to attach eggs.

Trails in the morning dew are often a sign that cutworms are on the move! Of course, other insects can also make such trails.

Notes: Black cutworm females attach virtually all of their eggs to the tips of grass blades. These are normally removed from golf course greens and tees through mowing. Therefore, it is recommended that the clippings containing eggs be disposed some distance from the greens and tees! First and second instar black cutworm larvae build small webbed shelters in the v-channel of turf leaf blades. They skeletonize the leaf surfaces within this protection. When they become third instars, the larvae drop to the ground and begin their habit of constructing protective burrows into the thatch and soil. They emerge from these burrows, generally at night, to feed on turf foliage. By the fourth instar, the larvae become cannibalistic – larger larvae regularly kill and eat any smaller caterpillars encountered! The larger larvae also tend to move and reestablish new burrows every few nights. The larger larvae can easily crawl 50 to 100 feet in a night to establish burrows in new areas. This is why we recommend treating the turf surrounding infested greens and tees (one to two boom widths, minimum) to prevent rapid reinfestation of the treated greens and tees.

Bronze cutworm larvae are green in the first three instars. They then take on their diagnostic coppery-brown color. Note the dark pronotal plate (just behind the head) with the white bars. The adults fly and lay eggs in September and October and the larvae often feed under the cover of snow. The larvae complete development by early June. A Connecticut home lawn damaged by bronze cutworms. Picture was taken in late April.

The true armyworm, often called the common armyworm, has dark and light colored stripes and a )-(-mark on the head. Armyworm larvae can seemingly eat turf down to the thatch “literally over night!” The adult armyworm is a simple buff color with a diagnostic small white spot on each wing.

Notes: The armyworm only periodically builds up outbreak populations. In most northern states across North America, this pest causes damage every three to five years. Mild winters followed by moderate, slightly dryer than normal spring and summer conditions appear to contribute to outbreaks. Over most of its range, armyworms overwinter as nearly mature larvae or pupae. In mid-spring, the adults lay eggs on grass blades, leaves of broadleaf weeds within turf or on permanent structures (light poles, fences, overhanging tree foliage). Each female can lay 100 to 300 eggs in a cluster and the females are often attracted to night lights where several moths may lay their eggs. The eggs hatch within a week to 10 days and the larvae tend to stay together while the feed on leaf tissues. The small instar larvae tend to hide during the day within the thatch and emerge to feed on leaves at night. When nearly mature (fifth and sixth instars), the larvae can eat considerable amounts of leaf tissue and they will commonly move side-by-side while eating down everything green in front of the moving “army.” This is where they get the name “armyworm.” During most seasons, armyworms complete two generations (more in southern states).

Fall armyworm thinning of bermudagrass rough adjacent to fairway. Fall armyworm damage to bermudagrass can appear as foliar disease, drought stress or other maladies.

Fall armyworm egg mass on tree leaf. FAW egg mass on post. FAW adult male. FAW larva showing white Y-mark on head.

Yellowstriped armyworm. Note the inverted Y mark on the head and the characteristic dark mark on the second thoracic segment and the dark triangles on each abdominal segment.

Notes: Fall and yellowstriped armyworms are common pests in the Gulf States where they breed and develop all year. Both species can fly northward and the adults are commonly found in cool-season turf zones after storm fronts move through. The larvae behave much like the common armyworm – moving as a front of caterpillars eating down everything green in front of them. Fall and yellowstriped armyworms rarely lay eggs on turfgrass leaves. They prefer to attach their egg masses to tree foliage, sides of buildings, sign posts and even the marker flags on golf greens. The adults seem to be able to sense that turf is below and the larvae simply drop to the turf after hatching. This is why fall and yellowstriped armyworm infestations generally appear to originate from the edges of golf course fairways, from under trees or adjacent to buildings. Fall and yellowstriped armyworms have a real knack for locating recently seeded or sodded turf that has been heavily fertilized.

Many species of skipper butterflies have larvae that feed on grasses, including turfgrasses. The fiery skipper is the best known. The adults are robust bodied butterflies that commonly feed on nectar. The larvae have a diagnostic constriction behind the head and the body is covered with velvet like hairs. Skippers rarely cause damage, but the larvae can occasionally make damage spots similar to the black cutworm.

Managing Turf Infesting Caterpillars Monitoring: A soap flush can help reveal most turf infesting caterpillars. While cutworms and armyworms surface quickly after a soap solution drench, sod webworm larvae often take 30 minutes or more to surface. Cultural Controls: Turfgrass with endophytes generally keep sod webworms and armyworms in check, but black cutworms do not seem to be susceptible to the endophyte toxins. Fertility should not be excessive as turf with high nitrogen content seems to be particularly attractive to caterpillars. Inspect golf green flags and markers for armyworm egg masses. Crush when found. Biological Controls: Many parasites, predators and diseases naturally keep caterpillar populations in check. Conserve these when possible by avoiding regular applications of insecticides. Insect parasitic nematodes are effective in controlling most caterpillars. Bacillus thuringiensis formulations are available for sod webworm and armyworm control.

Managing Turf Infesting Caterpillars (cont’d) Chemical Controls: Since most turf infesting caterpillars eat foliage, turf foliage is where the pesticide residues should be! In general, liquid applications work faster and more efficiently than granular applications. If the label allows, do not water in the application after spraying. Let the spray residue dry on the leaves where the caterpillars will feed, usually at night. Many pesticide labels require some watering after the application. These instructions should be followed or select another product that does not require watering after the application. Where cutworms or armyworms reinfest the surfaces of golf greens or tees within days of an insecticide application, treat the surrounding turf in an attempt to kill those larvae that could move back onto the greens or tees after effective pesticide residues have dissipated. Preventive applications of pesticides are not usually warranted for control of caterpillars. Visual observations and regular soap drenches can alert you to any caterpillar pest populations that are building up.

Dishwashing detergent is an effective disclosing aid for monitoring turf caterpillars. Use about two tablespoons per gallon of water and use two gallons of mix per square yard of turf. Test this solution in an inconspicuous area to determine if turf damage occurs. Joy, Dawn Ultra and Ivory Clear rarely cause phytotoxicity. Sod webworm larvae tend to take 20 to 40 minutes to surface after a soap drench. Occasionally, a second drench may be needed to coax all the sod webworms out. When flushed, the small caterpillars tend to crawl to the tips of grass blades in an attempt to dry off.

Turf Caterpillar Controls Insecticide Rate % Control # Tests Organophosphates Diazinon 5.5 94.0 4 Dursban 1.0 98.7 18 Dylox/Proxol 8.0 87.3 4 Orthene 5.0 92.3 4 Carbamates Sevin 4.0 96.8 5 Turcam 2.0 89.7 3

Turf Caterpillar Controls Insecticide Rate % Control # Tests Pyrethroids Astro 0.04 100.0 2 DeltaGard 0.08 94.5 2 Scimitar 0.02 96.8 5 Tempo 0.10 97.6 21 Spinosyn Conserve 0.3 90.1 6

Turf Caterpillar Controls Insecticide Rate % Control # Tests Chloronicotinoid Merit 0.3 48.5 7 Molt Accelerator (growth regulator) MACH2 1.0 86.5 7 Nematodes S. carpocapsae 1.0 bil 89.6 7 H. bact. 0.5 bil 67.0 4

Bermudagrass Mite Eriophyes cynodoniensis Sayed Bermudagrass mites cause internodes to stop elongating which results in tufting of the grass stems. This damage is often called “witchesbrooming.” Bermudagrass mites are microscopic, carrot-shaped mites (eriophyids).

Other Turf Eriophyid Mites Buffalograss mites cause witchesbroom tufts like the bermudagrass mite. The zoysiagrass mites cause marginal yellowing of leaves and often marginal rolling of the leaves.

Clover Mite Bryobia praetiosa Koch Clover mites are characterized by having elongate front legs which are orange-pink in color. The mites feed on turf leaves but cluster on structures to molt and lay eggs.

Winter Grain Mite Penthaleus major (Duges) Winter grain mite adults feed at night and are active from November into May, but may stop activity when daytime temperatures do not get above freezing. Winter grain mites have bright orange legs and dorsal anus openings.

Banks Grass Mite Oligonychus pratensis (Banks) Banks grass mites attack cool-season and warm-season turf. On St. Augustine- grass, they cause patches of yellow on the blades. On bluegrass and perennial rye, the mites cause blanching of the turf during the winter months.

Notes: Turf infesting mites rarely require implementation of controls. Their damage is often localized. Clover, winter grain and Banks grass mites feed by removing cell contents from turf leaves. This causes a blanching of the turf, but once the turf begins to rapidly grow, this damage is soon masked. Clover mites often invade nearby houses or buildings and they become significant nuisance pests in these situations – staining walls, upholstered furniture and clothing. Perimeter applications of pesticides (spraying the 5 to 10 foot of turf surrounding the building) registered for control of this mite usually stops the invasions. Be sure to check the seals of windows and doors and caulk where there may be access points. At present, there are very few miticides registered for turf use, but some insecticides, especially some pyrethroids, seem to have activity against the clover mite and winter grain mite. The bermudagrass and zoysiagrass mites are very difficult to control after the loss of diazinon. Most turf managers simply try to fertilize and water themselves through the mite damage.

Greenbug Aphid Greenbug aphid damage usually begins as a yellowing of the turf and if not controlled, they can cause the turf to turn straw colored. Greenbugs are green with black tipped cornicles. Winged and wingless adults are common.

Notes: There are several species of aphids that can be found attacking turfgrass. The greenbug (a species of aphid) is the most common species found causing damage to turf. This pest infests mainly cool-season turf and is most commonly found in lawns. There are several biotypes of the greenbug, some that specialize in various small grain crops, and some that attack cultivated grasses. Greenbug damage is often first found in the shady parts of lawns, under trees or adjacent to buildings. Their damage is first noticed as a distinctive yellowing of the turf with orange overtones, much like the visible damage caused by rust diseases. In fact, greenbug damage is often mistaken for rust. Greenbugs, like most aphids, produce honeydew and this attracts wasps, bees and flies to the area. Common predators, such as lady beetles and syrphid flies are also found where greenbugs are build up populations. Since greenbugs are commonly controlled with pesticides in field crops, may of the biotypes are resistant to some groups of insecticides. If an insecticide application does not seem to control this aphid, switch to another insecticide that is in another chemical group. For long term control, establish turfgrasses that contain endophytes. These symbiotic fungi produce toxins that kill greenbug aphids.

General Turf Insects – Identification, Biology & Principles of Control