Biocontrol potential of Neoseiulus longispinosus Evans (mesostigmata: phytoseiidae) against Tetranychus gloveri banks (prostigmata: tetranychidae) on adenium.

Abstract

The spider mite species Tetranychus gloveri Banks has emerged as a major pest of adenium in Kerala, South India. The sole reliance on synthetic acaricides for mite management has led to the development of resistance in T. gloveri populations, highlighting the need for alternative management strategies. The phytoseiid mite, Neoseiulus longispinosus Evans is a widely distributed predator of spider mites, adaptable to warm temperatures. The present study evaluates the efficacy of N. longispinosus against T. gloveri on adenium in the laboratory through functional and numerical response studies and in the polyhouse by a pot culture experiment. The functional response of N. longispinosus was studied on different life stages of T. gloveri, while the numerical response was studied on adult T. gloveri at different densities in a modified Munger cell. The pot culture experiment was conducted in completely randomised design (CRD) by releasing predators twice at 10-day intervals, at different predator-prey ratios of 1:25, 1:50, 1:75, 1:100, and 1:125 on adenium plants infested with T. gloveri. The functional response of N. longispinosus to all life stages of T. gloveri provided evidence for a Type-II response. The predator consumed all stages of T. gloveri, exhibiting the highest preference for the eggs, followed by the larvae, protonymphs, deutonymphs, and adult stages. The numerical response studies carried out at different densities revealed that the oviposition rate of the predator increased with an increase in prey density and prey consumption, recording a maximum of 3.05 eggs/day at the prey density of 12. In the polyhouse, the narrow predator-prey ratios of 1:25 and 1:50 significantly reduced the mite population to the tune of 94.50 and 61.95 per cent, respectively, after two releases of the predator, while the ratio 1:75 brought about 28.98 per cent reduction. However, wider predator-prey ratios were not effective.