Utilization of entomopathogenic nematodes to control insect pests in China

• Chinese Academy of Agricultural Sciences, China
• Guangdong Entomological Institute, China

This project follows the highly successful ACIAR project no. 8451, which demonstrated in China the potential of a method developed in Australia to control of insect pests using entomopathogenic nematodes. The method depends on an immature nematode penetrating the cuticle of a suitable insect species and moving into its body cavity. Here, symbiotic bacteria (Xenorhabdus spp.) released from the gut of the nematode multiply and kill the insect.
In project 8451, Australian scientists from the CSIRO Division of Entomology worked with Chinese scientists to further develop their technology for mass-rearing, storage and field application of nematodes, and conducted trials against a range of pests. Facilities constructed in Guangzhou and Beijing produced nematodes on a large laboratory scale; these were used in the field to control larvae of apple moth (Carposina nipponensis) in some orchards and cossid moth (Holcocerus insularis) on shade trees in the cities of Tianjin and Shi Jia Zhuang and in parts of Beijing.
While one application of nematodes over orchard areas ranging from 2 to 27 ha effectively replaced several applications of insecticide in controlling Carposina, the technique must be demonstrated over a much larger area (at least 667 ha) to obtain official national endorsement. Achievement of this goalthe aim of the present projectshould eventually lead to the successful control of China's major apple pest. The moth affects about 750 000 ha of apple orchards and, without insecticide or nematode treatment, would destroy 70% of all fruit. The potential annual loss of the pest has been estimated at A$760 million.
Isolates of the nematode Steinernema carpocapsae will be prepared in Australia and shipped to China in liquid nitrogen, where the research will involve visiting CSIRO scientists and colleagues from the Chinese Academy of Agricultural Sciences and the Guangdong Entomological Institute.
The project will require further development of technology for mass rearing, storage and field application. Collaborating scientists will develop factory-style procedures for mass rearing in two pilot plants, which will serve as models for future full-scale factories. At all stages of nematode production, quality-control protocols and procedures will allow cost analysisessential for evaluating the commercial potential of mass production of nematodes for the Chinese market against the conventional use of insecticides.
A pilot-scale factory would require a whole year to rear sufficient nematodes (about 360 tonnes) to control Carposina over 1 million ha, and these would need to be applied in the field over a 4-week period to attack the moth at its most susceptible stage. Thus the nematodes need to be stored for up to 12 months without loss of quality. The collaborators will investigate ways of extending the present storage period of only 3 months by focusing on the physiology of storage.
Field efficacy of the nematodes will also be scrutinised, in order to select strains or species that give the greatest pest kill, prolong their survival in the field and protect them from predatory fungi. Because only a small fraction of nematodes kill their target species under field conditions, far more nematodes than necessary are produced to achieve the desired result.
Benefits of the research include the replacement of chemicals to control apple moth (and later other pests) over large areas of China. This will reduce chemical input to the environment, improve the health of farmers and labourers through avoidance of contact with such chemicals, reduce chemical residues in food, and avoid the risk of insects developing insecticide resistance. The latter is inevitable if the present intensity of insecticide spraying is continued. Resistance to insecticides often depends on just a single gene. Development of resistance to biological control agents is much less likely.
Australian scientists will gain experience in the technology, which will spill over to the improved control of insects in Australia. In addition, Australia is at present developing a domestic and export nematode industry, which will benefit as a result of the ACIAR projects. Publicity from the results of the Chinese trials should help to increase farmer interest and use of nematodes in Australia, and eventually the technique may have application on a world-wide scale.