Insect parasitic nematodes give effective control of a range of insect pests of protected crops. A number of nematode products are available commercially in Europe but their markets are restricted due to the limited range of environmental conditions in which nematodes are effective. Most commercial products contain nematodes of the genus Steinernema because of technical difficulties with mass production of the alternative genus Heterorhabditis. Heterorhabditis has been found to be a more effective control agent of existing insect infestations but is less persistent than Steinernema in the absence of insect hosts. For this reason the major aim of the research project is to develop novel strains of Heterorhabditis with improved activity at low temperatures, resistance to drought conditions and persistence in the absence of insect hosts.
Insect parasitic nematodes (IPN), with their symbiotic bacteria, are effective parasites of insect pests under controlled conditions of temperature and humidity. Liquid fermentation technology has been adapted successfully for production of a United Kingdom strain of Heterorhabditis megidis. This has required studies on the symbiotic bacterium Xenorhabdus luminescens and development of growth conditions which retain the bacterium in the desired primary form. Growth medium composition has been optimized to give satisfactory yields of H megidis. It has also been necessary to pay attention to physical parameters, especially temperature, and oxygen levels in the growth medium. This has resulted in the design and construction of pilot scale fermenters which are now operating successfully.
Insect parasitic nematodes (IPN), with their symbiotic bacteria, are effective parasites of insect pests under controlled conditions of temperature and humidity. New IPN isolates and their symbiotic bacteria have been collected and novel strains developed by breeding, hybridization and mutagenesis. In order to screen new isolates for activity at low temperatures it has been necessary to develop simple bioassays that allow a rapid throughput of isolates. A number of bioassays have been developed that proved a reasonably good correlation with IPN performance.
Insect parasitic nematodes (IPN), with their symbiotic bacteria, are effective parasites of insect pests under controlled conditions of temperature and humidity. Bioassays have been used to study the effect of temperature on the various stages in insect kill by nematodes (eg nematode migration and penetration of insects). Results to date would indicate that penetration of insects by nematodes is the stage that is most sensitive to temperature.
The efficacy of IPN is strongly influenced by the quality of the production batch being evaluated. Quality tests, based on biochemical or morphological features, have been developed.
Techniques for production of axenic nematodes have been developed in order to allow construction of novel nematode/bacterium combinations.
The research tasks of the project are as follows:
testing and use of biotechnological methods to generate novel strains of insect parasitic nematodes (IPNs) which are improved over the wild types with regard to activity at low temperatures, drought resistance and persistence in the field;
development of technology for mass production of novel strains of nematodes;
evaluation of the effectiveness of novel nematodes in control of insect pests of horticulture and agriculture.
The novel nematode strains produced will be screened for improved characteristics with regard to activity at low temperatures (below 14 C), drought resistance and persistence in the absence of insect hosts. Bioassays for each of these characteristics will be developed. Design of the bioassays will be based on data produced during trials of existing Heterorhabditis strains for control of insect pests on unprotected horticultural crops. Promising novel nematode strains will be tested for mass production using technology already under development. Selected nematode strains will be produced in sufficient quantities to allow trials to be undertaken on a range of crops and insect pests. The novel nematode strains will be compared with existing commercial nematode products.
Funding SchemeCSC - Cost-sharing contracts
8931 BV Leeuwarden