The worm or larval stages of armyworms, cutworms and sod webworms are the most damaging stage of these insects on turfgrass. Although encompassing several genera of insects, the worm pests of turfgrass have similarities beyond just their larval form:
- Most are found across the U.S. and are most damaging from mid summer to fall.
- Heavy hatching and subsequent feeding damage generally follows dry or drought periods.
- The larvae are generally difficult to spot during the daylight hours, as they prefer to feed at night or early morning and sometimes during the day if the weather is overcast and wet.
- The adult moths are most active at night, during which time, adult females lay a large number of eggs. One armyworm female moth can produce about 14,000 eggs and one female cutworm moth may lay 300 to 2,000 eggs over several days.
- When the eggs hatch, larvae find suitable hiding places or construct their own for concealment. The sod webworm gets its name form the silken, web-like tubes that they construct in the thatch or soil.
| Armyworm - Pseudaletia unipuncta | Silverstriped Webworm - Crambus praefectellus |
| Fall Armyworm - Spodoptera frugiperda | Bluegrass Webworm - Paradediasia teterrellaus |
| Black Cutworm - Agrotis ipsilon | Larger Sod Webworm - Pediasia trisecta |
| Bronzed Cutworm - Nephelodes minians | Striped Sod Webworm - Fissicrambus mutabilis |
| Variegated Cutworm - Peridroma saucia | Tropical Sod Webworm - Herpetogramma phaeopteralis |
ARMYWORM: The young larvae are pale and green with a yellowish gray background color and longitudinal stripes on the back and sides. Armyworm's heads are honeycombed with dark lines. The incubation period is between three and thirty three days.
FALL ARMYWORMS: Fall armyworm larvae have a white upside-down Y on the front of the head and a black stripe along each side of the body. The larvae feed on herbaceous plants in addition to grasses. Eggs can hatch in two to ten days with four or more generations in the south and western portions of the U.S., with only one generation in the north.
CUTWORMS: Larvae are mostly hairless and spend daylight hours in tunnels they construct in the ground, emerging at night to clip grass. This damage is manifested as circular spots of dead grass or depressed areas. The bronzed cutworm is active in the fall and spring. In the southern U.S., cutworms remain active all year. Black and variegated cutworms may have two to four or four to six generations per year depending on the area of the country.
SOD WEBWORMS: Larvae are gray or light green to beige or brown with dark spots scattered over their bodies. Tropical sod webworms are light green. Most of the adult moths have a snout-like structure on the head. New sod fields and newly established lawns are preferred. Tropical sod webworm feeding damage gives turf a ragged appearance. There are two or three generations a year for most species, while tropical sod webworms have continuous generations each year below the frost line in Florida.
CONTROL. Generally, once symptoms of worm damage are noticed, the populations are at such high levels that immediate curative steps should be taken. This does not mean that damage cannot be prevented. However, with species that continually lay eggs, such as tropical sod webworms, continuous applications of residual insecticides may be necessary to control larvae of such species. Most of the organophosphorous insecticides, while effective against larvae present a problem at time of application, do not last long enough to provide control beyond a few days. Irrigation and rainfall may also affect the efficacy of such insecticides. A highly efficacious insecticide with long-term residual control of the various larval stages of worms is required to control all stages of these insects.
Courtesy of Zeneca Professional Products, Wilmington, Del.