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Fall Armyworms on the March

August 15, 2008
by Rick Brandenburg

Fall armyworm larva
Fall armyworm larva

Fall armyworm adult
Fall armyworm adult

Fall armyworm damage
Fall armyworm damage

by Brenda Watson for

Rick Brandenburg ,William Neal Reynolds Professor
Department of Entomology, North Carolina State University

I want to issue a very strong alert and warning for fall armywormsThey are showing up everywhere, and are a large threat to newly established turf and can also severely damage established stands. I expect serious problems in turf over the next 3 months.

The fall armyworm is a continuous resident of Central America, tropical South America and the West Indies. During mild winters, it may overwinter in coastal areas of southern Florida and Texas. Each spring, the fall armyworm spreads from these areas into the United States east of the Rocky Mountains and westward into southern New Mexico, Arizona and California.

The larvae are green, brown, or almost black. The dark head is marked with a yellow inverted "Y". There is a longitudinal black stripe along each side of the body and a faint narrow middorsal stripe. There are four black dots on the dorsal side of each abdominal segment. Fully grown larvae range between 1.38 and 1.97 in (35 - 50mm) long. The reddish brown - black pupae are about 0.5 in (13mm) long and are found in the soil. Adult moths have front wings that are dark gray mottled with light and dark markings. There is a white blotch near the tip of each front wing. The back wings are white.

The fall armyworm is most commonly associated with damage to bermudagrasses in the southern United States. However, it also feeds on fescue, ryegrasses, bentgrasses, bluegrass, and various small grain and grass crops. Infestations are associated with lush, green, dense grass. Problems most commonly occur in late summer and fall.

Larvae feed on all above-ground plant parts. Younger larvae skeletonize the most tender leaf tissue. Older larvae may consume most or all of the leaf tissue. Larvae move in groups from consumed areas to new areas. After fall armyworm feeding, bermudagrass, with proper management, usually regenerates. Feeding on cool-season grasses such as fescue and bluegrass may result in permanent damage.

Adult moths are most active at night and are attracted to lights. Light-colored objects adjacent to turf, such as flags on golf greens, goal posts, metal gutters and metal fences on athletic fields are favorite sites for egg deposition. Eggs hatch in 2-10 days. After 2-3 weeks, fully grown larvae burrow into the soil to pupate. Moths emerge in 10-14 days.

Flocks of birds feeding consistently in turf areas may indicate fall armyworm presence. If no larvae are seen, examine the turf for green fecal pellets and larvae. Soap flushes can be used to bring larvae to the surface. Except for home lawns and golf greens and tees, infested areas of less than 1,000 ft2 (92.9 m2) are seldom treated. Mowing before insecticides are applied may mechanically destroy a few larvae; in addition, it reduces the depth of the turf and ensures better coverage by spray applications. Light irrigation several hours before treatment may help to increase larval activity near the turf surface. Applications of biorational and chemical products should be made during periods when the larvae are active near the surface, usually early morning or late afternoon.

From the 2008 North Carolina Agricultural Chemical Manual

 

PEST

INSECTICIDE and FORMULATION

AMOUNT PER 1000 SQ FT

PRECAUTION and REMARKS

Fall Armyworm

azidirachtin* (Azatrol, Neemix, Turplex, etc.)

See label

 

carbaryl* (Sevin) 50 WP and baits

6 to 8 oz

Apply as a coarse spray in sufficient water for good coverage. Treat when first injury noted. Repeat as needed. Do not water into soil. Do not cut grass for 1 to 3 days after treatment.

 

halofenozide* (Mach 2) 2 SC 1.5 G

1.5 fl oz 1.0 lb

Can be applied two times per season at these rates.

 

pyrethroids* (Advanced Lawn, Bug-B-Gone, Deltaguard, Menace, Scimitar, Talstar, Tempo)

 

See label

 

spinosad A and D (Conserve) SC

0.25 to 1.25 fl oz

Rate varies with size and species.

 

trichlorfon* (Dylox, Proxol) 80 SP

 

1.5 to 3 oz

 

various entomogenous nematode and B.t. products

 

 

 

For More Information on Fall Armyworms:

  1. Contact Brenda Watson for extension handout sheets
  2. Visit TurfFiles Keyword Search for 'Fall Armyworms': http://www.turffiles.ncsu.edu/Insects/Fall-Armyworm