Whitegrubs: potato and cabbage pest in Indonesia and Western Australia

Page last updated: Wednesday, 9 May 2018 - 11:21am

Please note: This content may be out of date and is currently under review.

Whitegrubs are a minor pest of potato and cabbage crops in Indonesia but can be very damaging in 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 and 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

The Indonesian name for whitegrubs is "kuuk" and they are in the insect family Scarabaeidae.

Whitegrub larvae vary in size as these two species show. All whitegrub larvae live in the soilare crescent shaped, have a brown head and strong chewing jaws, three pairs of legs and a transparent body showing the stomach contents
Different species of whitegrub larvae vary in size

Whitegrubs are the larval stage of various species of beetles. They vary in size and colour but all have similar features.

Larvae are crescent-shaped with a brown head and prominent chewing mouthparts or jaws, three pairs of legs on the thorax and a transparent skin showing the stomach contents.

Larvae live in the upper soil layer feeding on the roots of many different plants.

Adults of whitegrubs are beetles that have a hard shell. A pair of wings is folded under their back
A typical whitegrub adult

Adults are hard-shelled beetles with thick wing covers over their backs to protect the wings that lie underneath. Despite their clumsy appearance, adults are strong fliers.

African black beetle is a species that occurs in both Indonesia and Western Australia. Adults are shiny black and about 1cm long
African black beetle adult

African black beetle is one species of whitegrub that occurs in parts of Indonesia’s potato growing regions as well as coastal south-west Western Australia.

Adults are black, shiny oval-shaped beetles about 10mm long. They spend most of their time in soil but will have mass flights during humid, warm to hot afternoons and nights, especially just before thunderstorms.

Feeding by African black beetle adults on young potato stems at ground level can kill them
Potato stem damaged by African black beetle

If present at plant emergence, adult African black beetles can kill stems of potato plants and cabbage seedlings by chewing them at ground level.

African black beetle adults can bore into potato tubers making them unmarketable
Damage to potato tubers by African black beetle adults
Larvae of African black beetle can bore into potato tubers making them unmarketable
Larva of African black beetle feeding on a potato tuber

Contact information

Stewart Learmonth
+61 (0)8 9777 0167

Whitegrubs: potato and cabbage pest in Indonesia and Western Australia

Author

Stewart Learmonth