New Zealand Tree Crops Association

Fruit Driller Caterpillar has reached Auckland:

A new Australian insect pest, the guava moth (Coscinoptycha improbana) that in the larval stage attacks a wide range of fruit has now reached Auckland, according to entomologist, Dr John Clearwater. Dr Clearwater has been working with the New Zealand Tree Crops Association (NZTCA) to develop methods for controlling the extent of damage caused by this pest. He has identified the moth in two separate sites in Auckland after observing growth of caterpillars in feijoas. Dr Clearwater will carry out a survey of the spread of the moth throughout Auckland, with funds supplied by the NZTCA. Members of the public can help in this survey by collecting a random sample of 50 windfall feijoas from the one site, box them and send to Dr Clearwater at the address listed at the end of the article (don't just collect fruit that appear damaged). Name the site from which they were collected!

Fruit damage by the fruit driller caterpillar (guava moth)
The so-called guava moth, or fruit driller caterpillar, was first identified about 8 years ago in Northland, and is particularly prevalent around the fruit-growing Kerikeri area. In the caterpillar stage, it eats the flesh of many fruit, such as plums, feijoas, peaches, nashi pears, tropical and strawberry guavas, citrus, loquats and macadamia nuts. (In comparison, the Codlin moth just eats the seeds of apples.) The wide range of fruit attacked suggests that a new name, the fruit driller caterpillar, more accurately reflects its host range. Damage to fruit at the early stage can be very difficult to detect as the grub enters the fruit directly from the egg case, leaving only a pin-prick hole. The inside of the fruit, however, can be a mass of grubs. Because of the wide range of crops that are attacked at various times of the year, the moth can be present throughout the year, not just in springtime. The fruits of some ornamental plants are also hosts to the caterpillars. Some New Zealand native plants are related to fruit species that are attacked, but so far appear to have escaped attack.

Biology of the fruit driller caterpillar (guava moth)
The caterpillar is small, growing to about 6 mm (¼ inch), becoming pink as it matures. After growing in the fruit it exits via a 1mm hole (it can even eat through a macadamia shell!) and drops to the ground to pupate. The 10 mm moth then hatches to continue the cycle. The moth is very similar to a New Zealand native species, the raspberry bud moth, with which it was initially confused. Positive identification requires an expert entomologist.

Spread of the fruit driller caterpillar (guava moth) in New Zealand
The moth has only gradually came south, being found around Whangarei last year. It has now jumped to Auckland. HortResearch have predicted that the Bay of Plenty and Hawkes Bay have an 85% probability of suffering problems similar to those in Northland. While Nelson could also be subject to guava moth predations, the seriousness of attacks is less able to be predicted. In Australia, it is found as far south as Tasmania, but is not a serious problem there. However, it is a major problem in Norfolk Island, where the Biosecurity Officer has contacted the NZTCA for information about control methods.

Control of the fruit driller caterpillar (guava moth)
General chemical sprays to kill the pest may not be effective, as the caterpillar is rarely exposed on the surface of the fruit. Systemic insecticides that penetrate the plant and are carried around the plant via the sap may be required, but are often not effective in trees. Due to the multiple life-cycles of the moth throughout the year, a year-long spraying programme would be required, which is highly likely to lead to the development of resistance by the moth to the spray. Home orchards are probably going to be a continuous source of new moth infestations.

Non-spraying methods that are environmentally friendly rely on the use of pheromones, the chemicals that the female moth use to attract males for mating. Dr Clearwater and his group developed the pheromone mixture used in the successful campaign to eradicate the white spotted tussock moth from Auckland some years ago. His group has identified the pheromones used by the guava moth and has field tested a pheromone-based control method in Northland orchards. Further testing and release of a commercial product is dependent on finding a source able to synthesize the pheromone mixture. The NZTCA and Dr Clearwater and his associates jointly hold a patent on the pheromones.

Involvement of the New Zealand Tree Crops Association in research on control of the fruit driller caterpillar (guava moth)
Following the identification of the moth in Northland by MAF and HortResearch in 2000, an NZTCA member in Kerikeri noticed a caterpillar eating her macadamias. The then president of the NZTCA, Diana Loader, brought a sample to Auckland, where it was identified by HortResearch as the guava moth. The Northern Branch of the NZTCA decided that control of this pest was necessary on behalf of its members and the general public. It held an appeal amongst members of the NZTCA and raised over $10000 for research into this problem. It engaged the services of Dr John Clearwater, well known for his research on pheromones. For the identification of the pheromones used by the guava moth, members in Northland grew the caterpillars and collected the hatched moths. Dr Clearwater sent the moths to a laboratory in Canada under quarantine control, where the pheromones used by the guava moth were identified.

Contacts

Dr Gordon Lees, Guava moth research co-ordinator, New Zealand Tree Crops Association.

Dr John Clearwater, Entomologist.
Address for forwarding feijoas: 63 Peter Buck Rd, Avondale

Update: 2008 May 08

John has been getting a good response of feijoas sent to him from members of the NZTCA and from the public following its publication in the Rodney Times.
From an update by John as of the end of April:
"All suburban samples (approximately 50 windfall feijoas per sample) are infested with Fruit Driller caterpillars and all rural samples are free of the pest. The most damaged of the samples came from Glendowie and contained 32 damaged fruit from a sample of 74 (43%), but the highest percentage of infection was from Grey Lynn (89%). Collections from Whitford, Bombay, Helensville, and Orewa are free of damage."

Gordon Lees; 8 May 2008