factsheet 152 Lawn Armyworm Spodoptera mauritia (Boisduval) [Family: Noctuidae

Several turf insects and related pests are common in Australia. Couchgrass mites suck plant juices. Some, such as mole crickets, lawn beetle and billbugs, live in the soil and damage plant roots. Caterpillars, which are the immature or larval stage of moths, including grass webworms and lawn armyworms, eat the grass leaves. To these groups can be added other insects and related pests, such as fleas, earwigs, millipedes, ticks, and snails that do not damage turf but may become nuisances because they bite people and crawl into houses, garages, swimming pools, etc.

Lawn armyworm are a severe and frequent pest of lawns in eastern and northern Australia and a lesser problem in the southern states. Severe infestations are more common in late summer and autumn. Early detection and treatment can prevent extensive damage caused by these pests.

The larval stage or caterpillar damages the turfgrass by feeding on the blade, crowns and stems. Young larvae may feed on the blades during daylight hours and the grass shows a silvering at the tips. They scrape away tissues from the surface of the blades leaving a colorless, membranous area at the tip of the grass blade. Watch for this sign of feeding damage. As the larvae increase in size they eat all the leaves and stems in their path and greener portions of the crown leaving only the tough old runners. Damaged areas take on a brown, dried up appearance. Active infestations are characterised by having a sharply defined advancing front between defoliated and green undamaged turf. With large active populations the front may move as much as 40 or 50 cm each night. Normally the denuded area spreads out from around the bases of buildings or trees and shrubs where eggs have been deposited. Older larvae feed at night and hide in the grass during the day. It is not unusual to have populations of armyworms, webworms, and other caterpillars at the same time in the same location.

Table 4. Host Range of Spodoptera mauritia Common Name Botanical Name

Couchgrass Cynodon spp. Flat sedge Cyperus rigidellus Mullumbimby couch, Kyllinga weed Cyperus brevifolius Nutgrass Cyperus rotundus Crabgrass Digitaria ciliaris Crowsfoot grass, Wiregrass Eleusine indica Paspalum Paspalum dilatatum Feather grass Pennisetum purpurem Pigeon grass, Bristly Foxtail Setaria verticillata Buffalograss, St.Augustine Grass Stenotaphrum secundatum Zoysia, Manilagrass Zoysia matrella Ryegrass (annual & perennial) Lolium spp Fescue Festuca arundinacea & spp Rhodes grass Chloris gayana Kikuyu Pennisetum clandestinium Blue couch Dicantheum sericeum Carpet grass Axonopus spp Wheat Triticum aestivum Rice

To prevent extensive damage by insect pests, frequent inspections of the turf should be made, especially during spring and summer, so that insect infestations can be found early and treatments applied promptly Insects are only one of the many causes of yellowish or brownish areas in grass. Diseases, nematodes, dry weather, and nutritional disorders are frequently responsible for such injury. It is important to be sure of the cause so proper treatment can be promptly applied to correct the trouble without the needless waste of pesticides and without further damage. To check the lawn for caterpillars, examine the grass in the off-color areas to determine if the blades have a chewed appearance. Lawn webworms rest in a curled position on the soil surface during the day and feed only at night. Small green pellets of excrement are numerous on the soil surface when the insects are present. Armyworms do not rest in a curled position. Early instars feed during the day and may be seen crawling over the grass. Mature instars feed primarily at night.

Females usually deposit their eggs on the foliage of shrubs and small trees, on buildings near outdoor lights allowed to burn in the evening or near windows from which light emanated, are used as egg laying sites. The entire life cycle takes approximately 42 days depending upon the temperature and humidity. Adults mate within a day after emergence from the pupa and start to lay eggs about 4 days later. Eggs hatch in 3 days, the larval (caterpillar) period lasts 28 days and the pupal period averages 11 days.

S:\1270 - ALMA\Website\Backup\docs\152.doc 1 of 3 10-Oct-14 Greatest activity occurs during the summer. Population studies in Sydney trapped adult moths attracted to an ultraviolet light. Monitoring of the caterpillar stage should commence early in January and continue at least until the end of March. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 9 17 23 8 16 0 4 3 42 2 0 0

Description Lawn armyworm caterpillars grow to one and one-half inches long and are greenish when small and dark brown when full-grown. They have a light mid-stripe along their backs and darker bands on each side of the mid-stripe. The mid-stripe ends in an inverted "Y" on the head. The one most common on turf is the lawn armyworm. The moths lay eggs on grass and on almost any object near turf areas. The newly hatched caterpillars cause very little visible damage to grass. Damaged areas are often first noticed along hedges and flowerbeds. Injury begins in a few spots which many times are only two or three feet in diameter. These spots enlarge, fuse, and encompass large areas of turf when heavy infestations are present. It is not until they are almost full-grown larvae that their feeding becomes noticeable, and then it shows up almost overnight. This, along with their night feeding habits, explains how extensive damage may occur before it is noticed. Armyworms pupate in the soil. Grass webworms differ from armyworms and skippers in size and feeding habits. The webworms feed primarily at night and remain in a curled position on or near the soil surface during the day. This habit makes them difficult to find. Adult moth Moths are nocturnal and commonly attracted to lights. Adults are common grayish brown with a wingspan of 1.2 to 1.6 inches. Males are slightly smaller (1.31.5 inch wingspan) and more vividly marked than the females. Egg Eggs are deposited in flat, felt-like masses, elongate-oval in outline, covered with light brown hairs from the tip of the females abdomen Larva Caterpillars of the LAW have 7 or 8 instars in their development. First instar larvae are pale green, about 0.05 inch long, emerge from the eggs and spin a silken thread to reach the ground. First to third instar larvae remain predominantly green as soon as feeding begins. As the larvae continue to grow, they become brownish with a pair of pale stripes down their backs. Patterns and stripes are present in the fifth to seventh or eighth instars. Mature larvae are 1.5 inches long with a pair of prominent jet-black marks on each body segment, with exception of the first thoracic and terminal segments, toward the center of the body inside the longitudinal yellow stripes. Spiracles are black. Development takes approximately 28 days. Pupa Pupation occurs in a loosely formed silken cocoon containing dirt, plant material and larval webbing. The pupa is normally found in the soil or grass debris at the base of the turf. It is reddish brown when fully hardened. Pupal period lasts from 10-14 days.

ACTION LEVELS The action or threshold level is when the pest population or turfgrass damage level has reached the point that a decision must be made whether or not to treat with an insecticide. The decision will depend upon the population of pest per unit area, the vigour and condition of the turf, and the intended use of the turf. Decision to treat is purely subjective, as pest populations are so dependent upon available moisture, temperature and vigour of turfgrass Larvae can be easily detected by putting out wet bags overnight and inspecting underneath the next morning. Spray when leaf loss first becomes obvious (ie the first small patches) and more than 20 caterpillars are found under each square metre of wet bag left overnight. Larval populations of LAW have been low probably due to the impact of predators, parasites and pathogenic organisms. A general level of 5 caterpillars per square metre indicates an increasing population and a pest management tactic should be considered. With more experience the action level may be fine tuned and more accurate.

MONITORING METHODS The use of water containing either pyrethrins or a detergent or flooding the sample area with water forces the larvae to come to the surface. Liquid irritants are more efficient than damp hessian bags and plywood boards left overnight.

CULTURAL CONTROL One of the simplest methods is to brush off egg masses on ceilings and walls of buildings. Use proper mowing techniques to keep thatch to a minimum. Avoid the buildup of thatch and remove it by scarifying or vertical mowing when it exceeds 6 mm thickness. Larvae tend to hide in the thatch. Fertilize turfgrass properly for the increase in succulence of grass encourages an increase in insect attack Overseed with grass varieties that contain "endophytic" fungi that discourage armyworms and some other insects from feeding on the grass. A number of perennial ryegrasses and a few tall fescues with this fungi are available. Lawns can be overseeded almost any time, but the autumn is the best time for these cool-season grasses. Because armyworms prefer turf that is dry and warm, do not allow your lawn to get too dry in the hot summer months. Water it well when rainfall is sparse. Watering in the late morning provides moisture to the grass and also keeps the soil surface cooler, making the area less attractive to armyworms. Cut the winter-active grass no shorter than 50 mm. Longer grass blades shade the soil and keep it cool. Maintaining a healthy lawn and avoiding the use of powerful insecticides encourage the buildup of a strong population of predator and parasitic insects that attack and control armyworms, especially at the egg stage. Wasps, earwigs, ladybird and other predatory beetles, ants, and mites all attack armyworms. Use of a general purpose, broad-spectrum insecticide on the lawn will destroy this natural line of defense, leaving the lawn open to attack by other pests. Accurate observations on the impact of these natural control agents is essential in making the decision whether or not to apply an insecticide on the armyworm population Many seed eating birds prey on caterpillars while raising their young. Encourage birds to set up housekeeping in your yard by providing them shelter and water.

CHEMICAL CONTROL Bacillus thuringiensis var. kurstaki spore is effective to control caterpillars. It is harmless to humans and safe to the environment. Its activity decreases with exposure to strong sunlight and extreme temperatures. Refer to the label for instructions on dosage rates, application information and precautions. An area treated with granular formulations should be watered down following application. Evening treatments are preferred and repeat applications may be necessary. The bacterium, Bacillus thuringiensis (commonly called BT), is a common bacterium found in soils. When first discovered, some strains seemed to affect the gut lining of certain insects, mainly leaf feeding caterpillars such as sod webworms and armyworms. Since discovery of this original group of strains, over 10,000 different strains have been characterised.

S:\1270 - ALMA\Website\Backup\docs\152.doc 2 of 3 10-Oct-14 Poison Active constituent Trade name(s) Manufacturer Schedule Biologicals: Dipel Abbott, Yates Delfin Syngenta Bacillus thuringiensis 0 Agree Syngenta FullBac Farmoz Melaleuca oil + Eucalyptus DePact 0 oil NutriGro Plus Yates Carbamates: Bendiocarb Ficam S6 Aventis Chemical Recovery Carbaryl Carbaryl S6 Chemspray Nufarm Organic Phosphates: Orthene Turf, Aventis Acephate S6 Lancer 750DF United Phosphorus Dursban Turf 500, Bayer Pyrinex 500 EC, Campbell, Chlorpyrifos S6 Chlorpyrifos 500EC, StrikeOut 500EC Farmoz Pennside, Diazinon S5 Campbell ProAm Diazinon Ethion Mustang S7 FMC International Isofenfos Oftanol S7 Bayer Lannate Crop Care Marlin Dupont Methomyl Nudrin S7 Aventis Electra 225 Farmoz Methomex 225 Nufarm Coopex Aventis Imperator Crop Care Permethrin S5 Grub & Insect Killer Barmac Permex Farmoz Dipterex 500 SL, Bayer Trichlorfon Lawn Grub Killer 500, S6 Chemspray Lepidex 500 Nufarm Merit Turf Bayer Imidacloprid Confidor 200SC S5 Bayer Provado 200SC Bayer Synthetic Pyrethoids: Dominex FMC International Fendona BASF Alpha-Cypermethrin S5 AlphaScud Farmoz Fastac BASF Beta-cyfluthrin Bulldock 8UL S6 Bayer Rage FMC International bifenthrin Talstar S6 FMC International Triumph Scotts Baythroid Turf S6 Bayer Solfac 50EW Bayer cyfluthrin Outlast Me S5 Bayer Baygon (various household sprays) Bayer Cyperkill Swift Sonic Nufarm Cypermethrin Cypermethrin S6 Sanonda Summit Cypermethrin Sumitomo Scud Farmoz Cislin Aventis Crackdown Aventis Decis Aventis Integral S5 Aventis K-otek deltamethrin Aventis Strafe Aventis Blitz S6 Pest Control Technologies Deltagard S6

Croppro D-sect Farmoz Ballistic Fluvalinate Mavrik Aquaflow S6 Syngenta Karate Crop Care lambda-cyhalothrin Icon S6 Demand BE SURE TO READ THE LABEL BEFORE APPLYING PESTICIDES

REFERENCE BRENNAN B M, 1979. Ornamental and Turf Pest Control. Miscellaneous Publication 174, University of Hawaii at Manoa. http://pestworld.stjohn.hawaii.edu/studypackets/ornament.html ELDER R, 2000. Sod Webworm in Pastures and Lawns. Department of Primary Industries Queensland. HERBISON-EVANS D, 2000. Australian caterpillars. http://www-staff.mcs.uts.edu.au/~don/larvae/noct/maurit.html http://www2.dpi.qld.gov.au/dpinotes/pastures/bi0240.html MITCHELL W, 1996. Management of Turf Pests. University of Hawaii http://www.extento.hawaii.edu/kbase/reports/turf_pest.htm National Registration Authority, Canberra. 2001. PUBCRIS database

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