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FALL ARMYWORM IN LAWNS

S. Bambara, Extension Entomologist

CAUTION: These recommendations were developed for North Carolina and may not apply to other areas.

FALL ARMYWORM, Spodoptera frugiperda (J.E. Smith), Noctuidae, LEPIDOPTERA


General Information

head of fall armyworm caterpillarFall armyworm caterpillars, sometimes known for marching in large "armies", are potential turf and pasture pests in late summer and fall. Consuming all green above-ground plant parts, they are capable of killing or severely retarding the growth of grasses. During most seasons, parasitic enemies keep fall armyworm larvae down to moderate numbers. Cold, wet springs seem to reduce the effectiveness of these parasites and allow large fall armyworm populations to develop. Conversely, years such as 2002 with mild winters and dry summer allowed early and sustained periods of infestation.

The fall armyworm has a wide host range but prefers plants in the grass family. Most grasses, including coastal Bermudagrass, fescue, ryegrass, bluegrass, Johnsongrass, timothy, corn, sorghum, Sudangrass, and small grain crops, are subject to infestation.

Biology

The mature green, brown, or black larva, 35 to 50 mm long, has a dark head usually marked with a pale, and a distinct, inverted "Y". Along each side of its body is a longitudinal, black stripe. There are four black dots on the dorsal side of each abdominal segment.

The moth has a wingspan about 38.5 mm. The hind wings are white and the front wings are dark gray, mottled with lighter and darker splotches. Each forewing has a noticeable whitish spot near the extreme tip. The minute light gray eggs are laid in clusters on any vegetation (shrubs and posts included) and are covered with grayish, fuzzy scales from the body of the female moth. The eggs become very dark just before hatching. The pupa, approximately 30 mm long, is originally reddish-brown and darkens to black as it matures.

Fall armyworms in NC probably overwintered as pupae in southern Florida. Egg-laying moths migrate northward throughout the spring and summer and arrive in North Carolina during mid-July. New moths may continue to appear into November. Each female lays about 1,000 eggs in masses of 50 to several hundred. Two to 10 days later the small larvae emerge, feed gregariously on the remains of the egg mass, then scatter in search of food. Unlike the nocturnal true armyworms, fall armyworms feed any time of the day or night, but are most active early in the morning or late in the evening. When abundant, these caterpillars eat all the food at hand and then crawl in great armies to adjoining fields. After feeding for 2 to 3 weeks, the larvae dig about 20 mm into the ground to pupate. Within 2 weeks, a new population of moths emerges and usually flies several miles before laying eggs. Several generations occur each year in North Carolina. Newly installed sod is more attractive to FAW and more susceptible to damage. Turf symptoms can first appear on lawn edges, and around areas near lights.

Control

lawn damage from Fall ArmywormThe fall armyworm is more difficult to control chemically than the true armyworm. Control of fall armyworms will be improved if you cut the turf prior to treating. A light irrigation prior to treatment may also help as will treating late in the day. Large fall armyworms are difficult to control. Don't expect 90% control. Pyrethroids will do a reasonable job as will Sevin (carbaryl). For professionals, products like Mach 2 and Scimitar and Acelepryn will also control turf feeding caterpillars, but don't expect miracles, especially if they are allowed to feed and grow for a week or more before treating. In warm weather the caterpillar can go from egg to pupa in 2 weeks. If the worms are very large (inch and a half long) then they will go into the soil very soon to pupate and control efforts may be a ineffective. Timing is important and a repeat application may be necessary in some situations. On a lawn, threshold is about one larva per square foot of turf. Soap disclosure solutions can be helpful for determining larval infestations. For specific control information, consult the NC Cooperative Extension Service recommendations. To view a Georgia study by Braman, Duncan, et al. regarding host plant resistance of turf types to FAW, link here. Among commercial Bermudagrass varieties, 'TifSport', showed the lowest FAW survival.

Grass Species and Endophyte Effects on Survival and Development of Fall Armyworm (Lepidoptera: Noctuidae)
S. K. Braman; R. R. Duncan; M. C. Engelke; W. W. Hanna; K. Hignight; D. Rush
Journal of Economic Entomology, Vol. 95, No. 2, April 2002 pp.487-492

Fall Armyworm Response to Insecticides and Turf Type.  S.K. Braman

Fall Armyworm Resistance in Texas Bluegrass, Kentucky Bluegrass, and Their Hybrids Jim Reinert

Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data.

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.

Other interesting links-

http://www.gaipm.org/top50/fallarmyworm.html

FAW Genetic Complexity

Other Resources

For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service.

Prepared by: S. Bambara, Extension Entomologist
photos of eggs and hatching by James Pearce.


Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
2003 NC Cooperative Extension Service

ENT/ort-128 January 2003
Web page last reviewed January, 2011 by the webperson.