NIW Research profile: Joe Roberts

Posted 24 June 2014

This entomology research profile has been produced as part of Harper Adams University's National Insect Week celebrations, June 23-29.

‘Novel Methods for Mass-Rearing Predatory Mites’ by Postgraduate Researcher, Joe Roberts

The research that I am conducting towards my PhD at Harper Adams University focuses on mites, which are a group of microscopic invertebrate animals that are related to spiders and ticks.

While there are more than 50,000 species of mites globally, I primarily concentrate on two different mites species: the two-spotted spider mite Tetranychus urticae and its predator, Phytoseiulus persimilis.

The two-spotted spider mite, aptly named due to the silk-like webbing it produces, is considered to be one of the most economically damaging crop pests within the agricultural industry, and can be found throughout more than 3800 different plant species worldwide.

The damage caused by this pest is considered by the European Union to be a significant threat to food security. As such, more than $1 billion is spent annually in an effort to try and counter the damage caused by two-spotted spider mites to economically important crops.

One method of controlling two-spotted spider mite populations within a crop is through the introduction of one of the pest’s natural predators: Phytoseiulus persimilis.

Phytoseiulus persimilis is an extremely active predatory mite that is specially adapted to move easily amongst the webbing produced by spider mites, and as such they exclusively feed on two-spotted spider mite. Despite the fact that the use of Phytoseiulus persimilis to control two-spotted spider mite infestation within crops has received considerable attention from the scientific community, there has been little development in the methods used to mass-rear them for this purpose.

Current mass-rearing methods rely on rearing huge numbers of two-spotted spider mites on plants in order to feed populations of Phytoseiulus persimilis to increase their numbers for harvesting and commercial sale as a control method. However, this mass-rearing process is dependent on the environmental conditions in which the rearing facilities are located, and in Northern and Western Europe it requires expensive, large, heated glasshouse infrastructures.

With increases in the fuels used to heat these glasshouses, there has been increasing pressure within the agricultural industry to keep Phytoseiulus persimilis production costs down and competitively priced. This has caused much of the industry to move their rearing facilities to North Africa; where the warmer climate removes the requirement for glasshouse infrastructures and therefore the fuel to heat them.

However, there is a trade-off that comes with the relocation or mass-rearing facilities as it generates long supply chains with extended periods of transportation that affect the quality of live products. 

The aim of my research is to find out is what attracts Phytoseiulus persimilis to feed exclusively on two-spotted spider mites, and then whether I can then use this information to ‘trick’ them into feeding on an artificial diet in a controlled environment room.

If possible, this would remove the need for two-spotted spider mite rearing, glasshouse infrastructures, and fuel for heating the glasshouse infrastructures; with the eventual aim of relocating the mass-rearing facilities back to Northern and Western Europe.

This would make the mass-rearing of Phytoseiulus persimilis more predictable, efficient, economical and robust against external factors that are out of the agricultural industry’s control. This would make Phytoseiulus persimilis more accessible to UK crop growers, who are under pressure from cheap crop imports and do not have the financial headroom to adopt alternative pest control systems.