This study aims to establish whether it is possible to mass-rear the specialist predatory mite Phytoseiulus persimilis using an “off-leaf” system that utilises an innovative artificial diet based on its natural prey, Tetranychus urticae, without negative impacts on predator fecundity, behaviour, development and performance.
Due to the increasing concerns surrounding the use of chemical pesticides as a method of pest control, there has been an increase in the demand for the development and utilisation of sustainable, environmentally friendly control methods. One alternative utilises biological control methods that exploit the natural enemies of a pest species in an attempt to manage pest population levels. There are a number of beneficial predatory arthropods commercially available on the market. Many of these beneficial arthropods are members of the arachnid taxon acari; more commonly known as mites.
One of the most widely employed beneficial predatory arthropods is Phytoseiulus persimilis Athias-Henriot as a method to biologically control the two-spotted spider mite, Tetranychus urticae Koch. Phytoseiulus persimilis is an extremely voracious and active predator that feeds exclusively on Tetranychus species. On the other hand, Tetranychus urticae is an extremely phytophagous pest that can be found globally, and is widely considered to be one of the most economically damaging arthropod pests within the agricultural industry owing to its ability to rapidly reproduce, withstand many plant toxins and feed on a vast variety of plant species. However, despite P. persimilis being used to control T. urticae since the late 1960s, there has been little development in the methods used to mass-rear these mites of biological control, thus causing production to be more inefficient and expensive than conventional chemical pesticides; negatively affecting their use in glasshouse crop production systems.
Current P. persimilis mass-rearing methods rely on a tritrophic system that requires the generation of large numbers of T. urticae, which itself involves the growth of bean plants, Phaseolus vulgaris, and maintaining suitable growing conditions. In Northern Europe, this requires large, expensive-, heated glasshouse infrastructures. Increasing fuel costs have led to the beneficial arthropod production industry in Northern Europe coming under enormous pressure to keep production costs down and their products competitively priced. This has caused much of the industry to move their production facilities to North Africa; thus creating long supply chains with extended periods of transportation that affect the quality of live products.
Research into an artificial diet resembling the eggs of T. urticae aims to develop an “off-leaf” mass-rearing method of P. persimilis that could be undertaken in environmentally controlled rooms, which would eliminate the requirement for: T. urticae rearing, Phaseolus vulgaris cultivation, large heated glasshouses, fuel overheads and ultimately the relocation of rearing facilities to Northern Africa. Consequently beneficial arthropod rearing would become more efficient, economical and robust against external factors that are out of the industry’s control and more accessible to UK crop growers who are under pressure from cheap crop imports and those who do not have the financial headroom to adopt beneficial arthropod pest control systems.