Identification and evaluation of soil borne predatory mites for root knot nematode control in protected organic cropping systems

Abstract: Root knot nematodes (RKN), Meloidogyne spp., are endo-parasitic nematodes that attack roots and are important pests in organic and conventional agriculture. Our general hypothesis was that soil predatory mites will prey on mobile stages of RKN, thereby reducing nematode density and plant damage. Our objectives were: 1) Collect and identify indigenous acarine species as potential candidates of predators of phyto-parasitic nematodes, using morphological and molecular tools. 2) Evaluate predation by these mites on mobiles stages of the RKN Meloidogyne javanica in a simple no choice system. 3) Identify and assess the potential of alternative prey for the conservation of soil predatory mites. 4) Evaluate predator control of RKN in potted plants and assess the effect of soil structure on predatory mite efficacy. For morphological and molecular identification of predatory mites, soil samples were collected and mites were extracted with Berlese funnels. Mites were sent to the Canadian Center for DNA Barcoding for sequencing. To test the prey suitability of free living non-parasitic nematodes (FLNPN) as alternative prey, we used the nematode Panagrellus redivivus as prey, and observed and recorded predation behavior of Gaeolaelaps aculeifer, Stratiolaelaps scimitus and Lasioseius floridensis. Predation and control of RKN were evaluated in 48 hour no choice experiments and 6-8 week potted plant experiments. Twenty species of mites belonging to the suborder Gamasina, were identified molecularly and morphologically, of which we have assessed 6 species in small arenas in no choice tests and 3 in potted plant trials. In our short-term experiments, nematode survival was significantly lower than the no release control in all species of predators evaluated. Our potted plant trials demonstrated that predatory mites can significantly reduce plant damage. Our direct recording of S. scimitus, G. aculeifer, and L. floridensis showed their ability to feed on the FLNPN P. redivivus. In summary, we have uncovered numerous indigenous potential candidates for nematode control. To improve and develop the biological control of plant parasitic nematodes we suggest that further research focus on the manipulation of soil structure and nutrients to conserve FLNPN and soil predatory mite populations.