Papuana beetles, pests of banana? Australia Minimize

May 2011. A question from a consultant engaged by the Australian Banana Growers Council about Papuana beetles. Are they pests of banana? These beetles are listed in Biosecurity Australia's Taro Import Risk Assessment as one of the pests of taro and mention is made of their feeding on banana. In Australia, there is only one of the species collectively known as taro beetles, and that is Papuana woodlarkiana. Are these beetles important pests of banana in other countries?

In reply members mentioned that Papuana (P. huebneri) was said to attack banana in south Tarawa, Kiribati, where it was also a pest of giant swamp taro, Cyrtosperma merkusii. However, in New Caledonia, Papuana uninodis (same species also occurs in Solomon Islands and Vanuatu) is present since the 1980s, but is rarely seen. I has never been recorded on banana and is even rare on taro. In Solomon Islands, Papua New Guinea and Irian Jaya, P. woodlarkiana laevipennis is said to damage small banana plants (possibly those that have not started to fruit) according to Stout (1982) Plant Quarantine Guidelines within the Pacific region. UNDP/FAO/SPEC Survey RAS74/427.

Further comments were sent by one of the moderators who thought there were reports of bananas being attacked by Papuana beetles in south Tarawa, probably because of restricted food sources there. As for Papuana being a pest of banana in Australia. That would be unlikely because of the treatment of the mats for nematode with Vydate and other pesticides. It was also mentioned that P. woodlarkiana could be devastating in coconut and oil palm nurseries.

In response, it was pointed out that there has been a huge change in the last 20 years and growers in north Queensland, where 80% of the bananas are grown, rarely use pesticides now. Instead, they use IPM measures with cover crops, biofumigants, soil ameliorates, including composts and ash, simple soil testing kits and the use of clean planting material (tissue cultured plants).

There have been other changes, too. Observations over the last decade suggest that the development of better irrigation methods (microsprinklers) and fertigation (fertiliser applied via the irrigation) have resulted in increased plant vigour and less plant stress in banana plantings. Other scarab beetles, such as the cane beetles which also feed on the banana roots and corm, have been less of a problem where the banana crop is well watered and it would seem there is a direct relationship between plant vigour and cane beetle pest attack.

A member of the agriculture department in Kiribati sent confirmation of infestation of bananas in south Tarawa. Relatively recently, Papuana beetles have become destructive on the crops. They feed on the corms, causing yellowing, and later browning, of the leaves. High infestations can kill the plants. During a recent drought, high numbers of grubs were found around cassava plants, although it was not confirmed that they were feeding on the tuberous roots.

Finally, a member who was with the taro beetle proejct of PRAP, the Pacific Regional Agricultiural Programme, wrote that adults of several species of Papuana beetles will feed on the base of banana plants. Banana are reservoir hosts for adults in the absence of taro. The following species P. woodlarkiana woodlarkiana, P. huebneri, P. uninodis, P. inermis, P. biroi and Eucopidocaulus tridentipes, all will feed on banana. They do not feed to fruits and foliage. P. woodlarkiana woodlarkiana is recorded in the Cape York area and is probably also present in the Torres Strait Islands. 

P. uninodis is present in Fiji, but has a restricted distribution and internal quarantine protocols are in place to prevent movement of plant material and soil from infested areas to other production areas. In Kiribati, P. huebneri is present on south Tarawa. PNG and Solomon Islands have a number of species, but with localized distribution except for P. woodlarkiana which with three subspecies is widely distributed.