Phthorimaea operculella (Zeller)
Potato tuber moth
Summary:The moth is grey brown flecked and 8 mm long with cream, green or pink black-headed caterpillars up to 20 mm long. It is major pest of potatoes across the world
Colour - Grey brown
Body - 8 mm
Wings - 12 mm wingspan. Fringed rear wings.
Legs - 6
Colour - Variable. Cream, green or pink and usually with a black head. Young larvae tend to be grey or yellow-white and mature larvae tended to be tinged with pink or green.
Body - Soft. 1-2 mm long then 4 instars to get to 12-20 mm long.
Mouthparts - Chewing
Head - Often black
Pupa - formed in a silken cocoon covered with soil and debris for camouflage.
Eggs - Oval. Initially pearly white turning yellow then blackish just before hatching. Laid singly on soil, tubers or the underside of foliage.
Eggs are laid on the soil, tubers or the underside of foliage. The eggs turn black just before hatching and a 1-2 mm caterpillar emerges. This goes through 4 instars to reach a final size of 12-20 mm. Caterpillars feed on the leaves and may drop onto tubers below or hatch in the soil and migrate to the tuber. Adult moths are most active at dawn and dusk, flying close to the ground between plants. Damage is often worst on the edges of fields where the moths invade.
There may be 6-8 generations over summer with all life stages being present at any one time.
The life cycle takes 4 weeks at 230C and 2 weeks at 370C.
Typically eggs hatch in 2-6 days, larvae mature in 16-24 days, pupae hatch after 6-9 days, and adult females begin to lay eggs after 2-4 days.
In stored potatoes breeding occurs all year whereas in the field it is predominantly in the summer and autumn. Specimens are most commonly seen from December to April.
Habitats:Stored potatoes. Potato or Solanum foliage or associated soil and tubers.
Origin and History:Pest of potatoes in Australia, New Zealand and USA.
World wide distribution.
May damage potato, tobacco, egg plant and tamarillo.
Damage to potato tubers is often causes the greatest economic losses. The caterpillar burrows just under the skin of the tuber then move deeper. Fras accumulates at the tunnel entrance. Damage may occur in the field or in storage.
The caterpillar stage burrows into leaves or tubers of potatoes. On the leaves they normally move towards the mid vein feeding between the upper and lower surfaces leaving "windows" or blisters. Leaf loss can result in yield losses.
Legislation:Management and Control:
Use pheromone traps to monitor moth numbers. Predators and cultural methods often keep numbers at low levels.
Maintain good soil cover over tubers to prevent caterpillars infesting tubers. Use overhead irrigation to help seal cracks in the ground allow caterpillars to access tubers.
Control volunteer potato plants.
After canopy senescence, insecticides may be required to kill caterpillars and stop moths laying eggs in the soil near tubers.
CSIRO. The Insects of Australia. Melbourne University Press. (1991)
Avidov, Z. and Harpaz, I. (1969) Plant Pest of Israel. Israel University Press. P
Horne, P. Boer, R de. and Crawford, D. (2002) Insect and Diseases of Australian Potato Crops. Melbourne University Press.
The Horticulture and Food Research Institute of New Zealand Limited (1998)
Collated by HerbiGuide. Phone 08 98444064 for more information.