PEST

NAME
Cutworms
Agrotis species

ORDER
Lepidoptera

FAMILY
Noctuidae

Description of the Pest
Cut worm larvae live in the soil, congregating in weedy areas; they chew off young seedlings at the base. They are smooth, thick fleshy grubs that vary in colour, from pinkish brown to olive green, or almost black. They grow up to 40mm long and 5mm thick. Larvae curl up when disturbed, pretending to be dead. Larvae burrow down into the soil to a depth of about 50mm to pupate. Adults are dark brown, hairy moths, with a wingspan of about 60mm.
These insects have a Holometabolouslife cycle, ie. When metamorphosisis observed during the pupalstage.

     

Appearance of the Pest
Adult moths are strong fliers capable of flying many kilometres laying eggs over a wide area. The eggs may remain dormant for several weeks until it rains or emerge within a few days under the right weather conditions.
Three similar species are commonly found in Australia:

•      Agrotis ifusa(Bogong moth) is up to 50mm across and has three spots on its forewing.
  
  •      Agrotis munda(pink cut worm); and
    
    •      Agrotis ipsilon(black cut worm).
      
      Agrotis munda
      
      Period of Activity
      Different species are active throughout the year, their prevalence being determined by rainfall and temperature. They are normally most active at night. Larvae will appear in greatest numbers when favourable environmental conditions produce lush growth.
      
      Susceptible Plants
      Cutworms prefer soft, succulent seedlings or fleshy annuals, perennials and a variety for ferns or orchids. They feed at night and remain in the soil during the day. They are most commonly found in soil that is infested with weeds or soil that is poorly drained and moist. Well-drained soils harbour less lava.
      
      Senecioand Dianthusspecies are attacked by the Cutworm (Peridroma margaritosa) which eats seedlings, leaves and flower buds. Under glasshouse conditions all stages of the lifecycle are present.
      
      Turf Grassesare attacked by several Agrotisspecies causing damage during different seasons according to there individual life cycle. All feed at night on the leaves when young and mature larvae shear plants stems at ground level.
      
      Damage Caused
      Young larvae feed on the lower epidermis of leaves. Adults attack stems and seedlings at the base, eating the soft new growth, on one side, or completely through. The damaged plant normally topples over (hence the common name). Mature plants may wilt or the foliage becomes yellowish as a result of the damage, but normally recovers.
      
      
      
      Cultural Control
      Weed removal and cultivation to improve the drainage of the soil will provide some reduction in of numbers. Seedlings may be protected by a physical barrier, (eg plastic tube pushed into the soil around the seedling). Heavily infected soil can be laid fallow with for several weeks to disrupt the life cycle or the soil can be covered in black or clear plastic until weeds and lava are dead.
      A molasses based bait that has hardwood sawdust and bran mixed with water creates a stick mass that the lava is attracted to but cannot escape. At sunrise they die from dehydration.
      
      BiologicalControl
      Natural predators such as birds, ground beetles and certain bugs help keep numbers down. Wasps and certain species of flies also attack the lava.
      Encouraging earthworms by mulching and increasing the humus level is an excellent way to rid the soil of lava.
      
      Chemical Control
      Chemical treatment (Carbaryl) may be effective if sprayed in the evening, when the caterpillars emerge to feed.
      Note
      Always read the label for registration details and direction of use prior to application of any chemicals.