------------------------- U of MN Extension Service FO-01008
Revised 2000

Managing Lawn and Turf Insects
Managing Lawn and Turf Insects

BLADE-DEFOLIATION: Sod Webworm moth larvae

Sod webworms (Crambus species and Parapediasia species, Family Pyralidae, Order Lepidoptera)

Identification: The adults of sod webworms are frequently called lawn moths. They are light-colored moths, which make short, erratic, darting flights above the turf and are attracted to lights at night (Figure 10). When resting they fold their wings back closely against their bodies, which gives them a very narrow appearance. Also, their heads appear to have a long snout. The moths lay their eggs in the lawn. The older larvae are a dirty white to light brown with darker spots and are about 3/4 inch long with a black head (Figure 11).

Figure 10. Sod webworm adult Figure 11. Sod webworm larvae
Figure 10. Sod webworm adultFigure 11. Sod webworm larvae

Damage, scouting, and management: The larvae feed at night on grass blades. During the day the larvae hide in silk-lined tunnels or burrows at or slightly into the soil surface. Some species damage plant crowns or roots as well as blades. Two generations can occur in Minnesota. Heavy infestations of the second generation may seriously damage large areas of turf. Although webworm adults are commonly seen, larval damage is uncommon in Minnesota. Look for dew sparkling on the webs in the early morning or at dusk. Use the flotation method to force the caterpillars to the surface, where they can be counted. In the flotation method, a soapy solution is poured inside a topless and bottomless can. The soapy solution is made by adding one ounce of mild dishwashing detergent to one gallon of water. It is best to scout for sod webworms in June and again in early August, since sod webworms have two generations per year. Tolerance is around 12 larvae/ft2. Water the lawn thoroughly a day or so before applying an insecticide. Then delay further water for at least three days after treatment.

Figure 12. Variegated cutworm
Figure 12. Variegated cutworm

BLADE-DEFOLIATION: Cutworm moth larvae

Cutworms (Family Noctuidae, Order Lepidoptera) Black cutworm (Agrotis ipsilon), Bronze cutworm (Nephelodes minians), Variegated cutworm (Peridroma saucia)

Identification: Full-grown cutworm larvae are about 1-1/2 inches long. The variegated cutworm’s color ranges from brown to gray (Figure 12). The black cutworm larvae are dark gray above and light gray below with black dots along the side of the body (Figure 13). The bronze cutworm’s color is a mottled burgundy brown. When disturbed cutworms roll into a ball (Figure 14).

Damage, scouting, and management: Black cutworm adults arrive in summer on southerly winds and larvae cannot overwinter in Minnesota. In golf courses, they are often found on greens surrounded by dense rough. The larvae feed on the grass blades or cut the grass off at the soil surface at night. During the day they hide in the soil or under debris. Aeration holes in greens are often utilized by cutworms as burrows. However, the presence of these aeration holes does not increase the number of cutworms. It is possible to have 1-3 generations per year.

Figure 13. Black cutworm Figure 14. Cutworm in ball
Figure 13. Black cutwormFigure 14. Cutworm in ball

BLADE-DEFOLIATION: Armyworm moth larvae

Armyworms (Pseudaletia unipunctata, Family Noctuidae, Order Lepidoptera)

Identification: These caterpillars feed on a variety of grasses including agricultural grass crops such as small grains and corn. Turf grasses are not commonly infested. Mature larvae reach 1-1/2 to 2.0 inches in length. Larvae are a dull yellow to gray with stripes running lengthwise along the body (Figure 15).

Damage, scouting, and management: Populations arrive as annual flights from overwintering southern populations. Populations of armyworms are typically kept in check by natural means, though population booms can occur, generally after a drought. Thresholds are not well developed.

BLADE-DEFOLIATION: Fall armyworm larvae

Figure 15. Armyworm
Figure 15. Armyworm

Fall armyworm (Spodoptera frugiperda, Family Noctuidae, Order Lepidoptera)

Identification: These caterpillars feed on a variety of grasses. Mature larvae reach 1-1/2 to 2.0 inches in length. Larvae have a black stripe down the middle of the back and on each side; four black dots on the dorsal side of each abdominal segment; and the face with a yellow inverted Y-marking.

Damage, scouting, and management: Populations arrive as annual flights from extreme southern populations. They are similar in size to armyworms. Populations of fall armyworms are typically kept in check by natural means, though population booms can occur, generally after a drought. Thresholds are not well developed.

BLADE-SUCKING: Leafhopper adults and nymphs

Leafhoppers (Family Cicadellidae, Order Hemiptera)

Figure 16. Leafhopper
Figure 16. Leafhopper

Identification: A number of species can be found in turf. During some seasons these very tiny green or gray insects become so numerous that when disturbed into flight, they rise like a cloud of dust. Most of the grass-infesting leafhoppers are less than 1/4 inch long, narrow, and tapered from head to tail (Figure 16).

Damage, scouting, and management: Populations arrive as annual flights from southern populations. Eggs are inserted into leaf tissue. Leafhoppers are sap-sucking insects, and their damage usually appears as irregular patches in which the grass has yellowed or bleached-out lesions. Established lawns are seldom seriously damaged. Eggs hatch in one to two weeks, and the young nymphs begin to suck on grass blades. Control is suggested for new lawns only and thresholds are not well established.

BLADE-SUCKING: Aphid adults and nymphs

Greenbugs (Schizaphis graminum, Family Aphididae, Order Hemiptera)

Identification: Greenbugs are aphids that can damage established turf. The insects are small and yellow to green, and they can be found by sweeping your hand over suspected areas (Figure 17).

Damage, scouting, and management: Greenbugs are carried into Minnesota by southerly winds, so they can show up overnight. Aphid suck the sap from blades and the damage appears as pale areas often with yellow streaking. Damage is almost always near areas of the lawn shaded by trees or shrubs. Bluegrass is a prime target for greenbug attacks. Control is suggested when damaging greenbug populations are first noted, as they reproduce very quickly. Greenbugs are usually first found in late July or August.

Figure 17. Aphid
Figure 17. Aphid

BLADE-SUCKING: Chinch bugs adults and nymphs

Chinch bugs (Blissus species, Family Lygaeidae, Order Hemiptera)

Identification: Chinch bugs on turf are rare in Minnesota. Obtain positive identification before attempting control. Immature bugs are red, but become dark as they mature. Adults are 1/5 inch long, have a head that is narrower than the thorax (shoulder), and have light colored forewings with a conspicuous black triangle midway along the outside margin (Figure 18). Immature chinch bugs (nymphs) are similar in appearance to adults except smaller with the wings absent or only moderately developed.

Damage, scouting, and management: Chinch bug populations of 20 to 25/ft2 can cause damage and may warrant treatment.

Non-Damaging Insects that Live in the Turf

There are a few very common insects or insect relatives that live in grass, but do not cause direct feeding damage.

Figure 18. Chinch Bug Figure 19. False Chinch Bug
Figure 18. Chinch BugFigure 19. False Chinch Bug

BLADE-SUCKING: False chinch bug adults and larvae

False chinch bug (Nyssius species, Family Lygaeidae, Order Hemiptera)

Identification: False chinch bugs (Nyssius sp.) are small gray bugs resembling true chinch bugs (Figure 19). They are more frequently encountered on herbaceous plants, although they can feed on turf when the preferred food is not available. False chinch bugs are approximately 1/4 inch long, brown, and generally found in dead areas of the turf. They can be distinguished from the true chinch bug by the absence of a conspicuous black triangle on the outer wing margin and by a head that is about the same width as the thorax (shoulder).

Damage, scouting, and management: Control is not recommended.

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