Common Armyworm

Mythimna convecta, Mythimna loreyimima

Family: Noctuidae

Order: Lepidoptera

Description:

Adult

Night flying moths with eyes that reflect orange light.

Colour -

Body - Medium size. Long hair scales. Stout body.

Wings - 2 Pairs. Membranous. Hairy. Wingspan of 40 mm.

Mouthparts -

Antennae - 3 segments.

Legs - Broad overlapping scales. Feet (Tarsi) have 5 segments.

Head - Broad overlapping scales. Large rounded compound eyes.

Thorax - Broad overlapping scales. 3 segments. Front segment much smaller. Hairy

Abdomen - Broad overlapping scales. 7-11 segments. Spiracles on segments 1-7. Hairy

Egg - Oblong. Smooth. Inserted into the leaf sheaths of grasses.

Habits - Can't fly when cold. Migrates southwards to infest crops in spring.

Caterpillar -

Colour - Dark when in high numbers and light when in low numbers. Prominent white stripes on the collar behind the head.

Body - 40 mm long, 5-8 mm wide.

Mouthparts - Chewing.

Antennae - Short. 3 segments.

Legs - 5 segments. Single claw on end.

Head - Hard.

Thorax - 10-11 segments. Spiracles on segments 1 to 8. Prolegs on segments 3, 6 and 10.

Abdomen -

Habits - Herbivorous. Feed at night mainly. Square green droppings are often seen at the base of cereal plants under attack.

Pupa -

Biology:

Life Cycle:

3 to 4 generations per year and may over summer on summer green grasses or volunteer cereals. The moth lays eggs in the sheaths of grasses. These hatch into caterpillars which feed on leaves. The larger caterpillars climb the plant at night to lop heads in spring. Caterpillars fall to the ground to pupate before emerging as moths that may migrate with the prevailing winds. In spring, egg laying to head lopping may only take 3 weeks.

Habitats:

Origin and History:

Distribution:

Significance:

Native to Australia. Caterpillar is a pest of cereals and grasses (especially ryegrass). Most damage usually occurs from September to January.

In W.A. south coastal course grain crops are most severely affected. They chew through the neck of barley just below the head causing it to fall to the ground. Once head lopping starts, a large amount of damage may be done in a short time. In winter they may chew leaves but are seldom an economic problem.

Management and Control:

They are preyed on by native parasites, and a number of wasp species have been introduced for biological control, so spraying is not usually required every year. High temperatures can also quickly control an outbreak.

Thresholds:

Barley - 2 large larvae per square metre as the crop is maturing. Look for signs of head lopping and faecal pellets near the base of plants. During the day, search the ground and under clods and debris for larvae.

Related Species:

Bogong moth, Cluster caterpillar, Common Armyworm, Corn Earworm, Cutworms, Helicoverpa or Heliothis, Inland Armyworm, Lawn Armyworm, Loopers, Native budworm, Southern Armyworm.

Similar Species:

References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991) p108, 831, 914, 948parasites.

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p46.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.