Loopers: potato pest in Indonesia and Western Australia

Page last updated: Wednesday, 1 July 2020 - 10:00am

Please note: This content may be out of date and is currently under review.

Loopers are a relatively minor pest of potato crops in both Indonesia and Western Australia.

The Department of Primary Industries and Regional Development, Western Australia has worked with the Indonesian potato industry to increase the productivity of Indonesian crops planted with WA seed potatoes.

Improved productivity requires accurate identification of pests in potatoes as well as in the cabbage rotation crop.

As well as helping Indonesian farmers, this information will assist Western Australian seed potato exporters understand the challenges their Indonesian customers face.

Identification

Looper’s Indonesian name is "ulat jengkal" and the scientific name is Chrysodeixis sp.

Looper moths are about 25mm long and upper wings are brown with silver marks
Looper moths are about 25mm long

Looper moths have a wingspan of about 50mm. The upper wings are brown with silver marks, while lower wings are pale brown.

Looper moths lay single eggs about 0.5mm diameter
Looper moths lay single eggs about 0.5mm diameter

Eggs are about 0.5mm diameter and white when first laid. They darken just before hatching.

Larvae are bright green with two white stripes along their back
Larvae are bright green with two white stripes along their backs

Eggs hatch into a larval stage which feeds on leaves.

All stages of larvae move with a characteristic looping action.

Looper larvae do not eat main leaf veins; heavily infested plants are tattered
Looper larvae do not eat main leaf veins, but heavily infested plants are tattered

Larvae feed continuously and as they grow, leaf loss can be rapid. Large numbers can defoliate crops.

When mature, looper larvae form a cocoon within a silken case in a rolled up leaf
When mature, looper larvae form a cocoon within a silken case in a rolled up leaf

When larvae are mature, they web leaves together or roll single leaves to form a silk chamber in which they form a cocoon. The adult moth later emerges from this silk chamber.

Management

Looper larvae will not be a pest in all crops. Monitor crops weekly to check for larvae or characteristic damage on leaves.

When an estimated 20 to 25% of the leaf canopy has been removed by looper larvae, apply insecticide.

Because loopers eat a lot of leaf, the stomach poison bacteria BT (Bacillus thuringiensis) is an effective biological insecticide. BT is safe for humans and only kills leaf feeding moth larvae. Therefore natural enemies of loopers and other pests will not be killed by it.

Looper larvae are attacked by a range of natural enemies – diseases, predators and parasites.

Acknowledgment

Funding for this work to support Indonesian potato farmers and WA seed potato exports was provided by ACIAR (the Australian Centre for International Agricultural Research) and the Department of Primary Industries and Regional Development, Western Australia.

Contact information

Stewart Learmonth
+61 (0)8 9777 0167

Author

Stewart Learmonth