Combining two predatory mite species (Phytoseiidae) to control two-spotted spider mites in greenhouse strawberry production

Strawberry is an important economic crop worldwide, whereas two-spotted spider mites (TSSM, Tetranychus urticae) is the major pest in fruit production. To produce the organic and safe fruits in greenhouses, we selected two strawberry varieties that are most widely planted in northern China with popular taste to study the TSSM control efficiency by two predatory mites of Phytoseiulus persimilis and Neoseiulus californicus. We comprehensively evaluated the control methods by analyzing TSSM population dynamics, predatory mite numbers, leaf chlorophyll content, fruit weight, sugar content, and the cost of investing in predatory mites. We found that the mite-resistant variety Miaoxiang can largely maintain TSSM at a relative low-density, and N. californicus can provide sufficient control against TSSM during the whole growth season. When TSSM density was high in Suizhu, the combined use of predatory mites led to a substantial reduction of 85.99% in pest numbers, all at reasonable prices. Our fieldwork has demonstrated the crucial importance of pest monitoring and early warning systems in determining the application of biocontrol agents, taking into account factors such as TSSM population size and rate of expansion. These findings strongly suggest that utilizing suitable biocontrol agents represents a promising approach for effectively managing TSSM infestations in greenhouse strawberry production.