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
Fall
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 probably overwinter as pupae in the Gulf Coast
region of this country. 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
The 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) and even Orthene (acephate) against small worms.
For professionals, products like Mach 2 and Scimitar 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://iaa.umd.edu/umturf/Insects/Armyworm.html
http://www.gaipm.org/top50/fallarmyworm.html
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, 2009 by the webperson.