Photo 3. Red pumpkin beetle, Aulacophora sp., showing the groove on the thorax. Compare with Monolepta.
Pumpkin beetle, red pumpkin beetle
Aulacophora species. The identification of the species in the Pacific is uncertain. Aulacophora similis has been recorded from Fiji, Samoa, Solomon Islands, and Tonga. But it is more likely that the species in these countries is Aulacophora adominalis.
Uncertain. Asia, Oceania. A revision of the species is necessary to clarify distribution in Oceania and elsewhere.
Cucurbits are hosts; common cucurbits are cucumber, melon, pumpkin, watermelon and gourds. Similar species are pests of these plants in Papua New Guinea, Indonesia, the Philippines, Japan, India, and Australia.
The life cycle of Aulacophora similis is as follows. Females lay yellow, oval eggs singly or in batches in soil around the base of the host. After 5-15 days, they hatch, and the cream-white young (called 'larvae') burrow into the soil to feed primarily on the roots. Four moults occur over 14-25 days, and then the larvae enter the pupal stage in an earth chamber; this lasts another 7-20 days before the adults emerge (Photos 1-3).
Females lay up to 500 eggs, and live as long as 10 months. This means there are several overlapping generations each year.
Interestingly, the adult beetles cut discs from the leaves (Photos 2,4&5). It is possible they do this to stop the flow of sap into these discs before feeding on them. There may be substances in the sap which are toxic to the beetle.
Often, several beetles are found feeding together on the same leaf while others are untouched (Photo 6).
Adults feed on leaves, chewing large holes. Seedlings are particularly susceptible, and so are young plants after planting out. The damage to young plants can delay crop maturity. Damage also occurs to flowers and small fruit.
The larvae probably damage roots and stems, but evidence of this has not been reported from Pacific island countries. This type of damage may allow entry of other organisms, especially fungi.
Look for red oval beetles, about 8 mm long, on the leaves and flying between them. They are often in groups on both young and old leaves. Look for the circles eaten by the beetles, and the large holes in the leaves between the veins. Often, groups of beetles will attack the same leaf, leaving only the veins, before moving to other leaves. Adults are strong fliers, and quickly take to the wing when disturbed.
A similar coloured leaf beetle, Monolepta (now called Candesia), has a dark area on the triangular piece at the base of the wing cases. It also has a smooth thorax - the part behind the head. By contrast, Aulacophora has a groove across the thorax (this can be seen in Photo 3). (See Fact Sheet no. 53 - Monolepta.)
There is little known about the natural control of these beetles. The beetles contain chemicals that visual predators do not like, and are avoided by them. The bright colours of this beetle warn predators that they are distasteful.
Fast growing varieties are more likely to outgrow the damage caused by the beetles.
AUTHORS Helen Tsatsia & Grahame Jackson
Photos 1&3 Graham Teakle, Canberra. Photos 2&3 Mani Mua, SPC, Sigatoka Research Station, Fiji.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
This fact sheet is a part of the app Pacific Pests and Pathogens
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