How to Manage Pests

UC Pest Management Guidelines

Although damage is similar, armyworms are distinct from cutworms in their behavior. While cutworms are usually solitary feeders, armyworm eggs are laid in masses and larvae will feed as a group. When populations are high and food is scarce, armyworms will move as a group, feeding indiscriminately on plants in their path. Variegated cutworms are also known to march like armyworms when populations are high.

SUSCEPTIBLE SPECIES
All turfgrass species.

DAMAGE
Cutworms and armyworms are active from mid-March to October. They feed on leaves and crowns and may cut off plants near the soil surface. Larvae feed at night and hide in the thatch layer or in a burrow in the soil during the day. Turfgrass may be closely clipped around aeration holes, which larvae commonly occupy. Damage appears as circular spots of dead grass or depressed spots. Armyworms, especially, prefer damp areas.

MANAGEMENT
The first step in managing a population of armyworms or cutworms is to dethatch the turfgrass and ensure that irrigation does not cause wet areas in the turf. When monitoring indicates a need to treat, treatment choices include parasitic nematodes and Bacillus thuringiensis (Bt).

Biological Control
Larvae are parasitized by braconid wasps (Apanteles spp.) and by tachinid flies. Birds also commonly feed on armyworms and cutworms. The extensive contact noctuid larvae have with soil or thatch makes Steinernema carpocapsae nematodes a valuable control measure. Bacillus thuringiensis subsp. kurstaki (Bt) is not as effective against cutworms and armyworms as for sod webworms and should only be used during the first and second instars.

Cultural Control
Remove thatch to eliminate much of the daytime resting habitat for larvae. Avoid wet areas by irrigating according to evapotranspiration needs of turfgrass, because armyworms prefer laying eggs in damp areas containing stressed plants.

Monitoring and Treatment Decisions
Threshold levels are five larvae per square yard. Conduct a drench test (see GENERAL INFORMATION) to determine the infestation level. Consider treatment when there are more than five larvae per square yard. Mow and irrigate the site before applying insecticide and do not mow or irrigate the turfgrass for at least 24 hours after treatment unless nematodes were applied, in which case apply a post-treatment irrigation. When Bt is applied, do not irrigate for 2 days after treatment.

Common name
(trade name)		Amount/1000 sq ft**
Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
A.	ACEPHATE
	(Orthene Turf, Tree, and	Cutworms: 1.2-2.4 oz
	Ornamental Spray)	Armyworms: 0.5-1.2 oz
	COMMENTS: For use on golf courses and sod farms only. Odorous. Up to 2.4 oz material/1000 sq.ft. can be used for black cutworm.
B.	AZADIRACHTIN
	(Ornazin, etc.)	Label rates
	COMMENTS: Can be used on both warm and cool-season grasses.
C.	BACILLUS THURINGIENSIS ssp. KURSTAKI
	(various products)	Label rates
	COMMENTS: Only effective on early instar larvae. Repeat application may be necessary. Breaks down rapidly in sunlight and washes readily off leaves. Do not irrigate for 2 days after treatment.
D.	CARBARYL*
	(Sevin)	3 fl oz
E.	CHLORPYRIFOS
	(Dursban Pro)	1.5 fl oz
	(Dursban) 50W WSP*	0.75 oz
	COMMENTS: For use in turfgrass production and on golf courses only. This product is highly toxic to birds and aquatic invertebrates. State and federal agencies have determined that waterways have been impaired by the use of this material. Do not apply in such a manner that it will get into storm water drains.
F.	CYFLUTHRIN*
	(Tempo) 20WP	0.176 oz (5 grams)
G.	DELTAMETHRIN
	(DeltaGard T & O) 5SC	0.2-0.4 fl oz
	COMMENTS: Apply as a broadcast spray in a minimum of 2 gal water/1,000 sq.ft. Delay irrigation or mowing for 24 hours after application. Not for use on sod farms or in turf grown for seed production.
H.	SPINOSAD
	(Conserve SC)	Armyworms: 0.25-1.2 fl oz
		Cutworms: 0.8-1.2 fl oz
	COMMENTS: Use lower rate for control of light infestations of small larvae; the higher rate should be used for control of heavy infestations and large larvae. Delay watering or mowing of treated area for 12-48 hrs after treatment. Do not reapply within less than 7 days.
I.	STEINERNEMA CARPOCAPSAE	25 million
	COMMENTS: Store nematodes properly before use as directed. Apply to warm, moist, but not soggy soil. Several irrigations may be needed during 2 weeks after application to keep soil moist. Apply during the coolest time of day in hot areas.

**	Apply spray in 2-5 gal water/1000 sq ft
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Insects and Mites
H. S. Costa, Entomology, UC Riverside
R. S. Cowles, Entomology, Connecticut Agricultural Experiment Station, Windsor, CT
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
H. K. Kaya, Nematology, UC Davis
Acknowledgment for contributions to the insect and mite section:
K. Kido, Entomology, UC Riverside

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