Combined releases of predatory mites and provisioning of free-living nematodes for the biological control of root-knot nematodes on `Micro Tom tomato'

Authors: AZEVEDO, LETÍCIA - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); MOREIRA, MATHEUS - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); GRILLI, GRAZIELA - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); BORGES, VINICIUS - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); DE MORAES, GILBERTO - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); INOMOTO, MARIO - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); VICENTE, MATEUS - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); DESIQUEIRA, MAISA - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); PERES, LAZARO - LUIZ DE QUEIROZ COLLEGE OF AGRICULTURE (ESALQ); RUEDA-RAMIREZ, DIANA - UNIVERSIDAD DE COLOMBIA; CARTA, LYNN; MEYER, SUSAN; MOWERY, JOSEPH; Bauchan, Gary; Ochoa, Ronald - Ron; PALEVSKY, ERIC - VOLCANI CENTER (ARO)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2020
Publication Date: 4/13/2020
Publication URL: https://handle.nal.usda.gov/10113/6888053
Citation: Azevedo, L.H., Moreira, M.F., Grilli, G., Borges, V., De Moraes, G.J., Inomoto, M.M., Vicente, M., Desiqueira, M., Peres, L.P., Rueda-Ramirez, D., Carta, L.K., Meyer, S.L., Mowery, J.D., Bauchan, G.R., Ochoa, R., Palevsky, E. 2020. Combined releases of predatory mites and provisioning of free-living nematodes for the biological control of root-knot nematodes on `Micro Tom tomato'. Biological Control. https://doi.org/10.1016/j.biocontrol.2020.104280.
DOI: https://doi.org/10.1016/j.biocontrol.2020.104280

Interpretive Summary: Nematodes are microscopic roundworms that include beneficial species in soil as well as parasites of plants and animals. These parasites cause billions of dollars of damage to crops in the U. S. each year. Farmers have a serious problem controlling them, as the pesticides traditionally used in soil against plant parasites are highly toxic and nearly unavailable. One problem with the development of biological control agents such as bacteria or mites against plant-parasitic nematodes is that their effectiveness is variable. For example, efficacy of the predatory mites in controlling nematodes depends on the soil ecology, especially the numbers and types of different nematode species in the soil. This unpredictability may be improved by using bacterial-feeding nematodes as food for the predatory mites that are applied as biocontrol agents. Bacterial-feeding nematodes are free-living and easily grown, and could be used to fortify the predatory mites for their next most important task of eating plant-parasitic nematodes, thus reducing nematode damage to plants. Therefore, scientists from Israel and Brazil isolated a species of bacterial-feeding nematode from pasture soil, grew it on bacterial slime, and fed the nematodes to a commercial predatory mite which reduced plant-parasitic root-knot nematodes on tomato roots in a screened-in greenhouse. Aside from feeding the mites, the free-living nematodes were also associated with increased nitrogen and potassium nutrition of tomato leaves. Scientists from Israel and the USDA-ARS, Beltsville, MD also observed the interactions between a free-living, bacterial-feeding nematode and two plant-parasitic nematodes in a special arena under a low-power microscope, and then flash-froze and imaged them at very high magnification. This close-up view showed how different mite appendages held and consumed the free-living and parasitic nematodes in a similar manner. This information will be used by researchers and growers to improve non-chemical control of a major, worldwide soil pest.

Technical Abstract: BACKGROUND: Soil predatory mites (SPM) feed on a diverse diet making them excellent candidates for conservation biocontrol. Free-living nematodes (FLN) are commonly found in soils and serve as prey for many SPM. Our goal was to determine whether conservation biological control of plant parasitic nematodes (PPN) by SPM could be enhanced by provisioning FLN with their culture medium (FLNCM). First, we performed low-temperature-scanning electron microscopy (LT-SEM) of predation on a FLN and two PPN. Then we conducted two experiments on dwarf tomato plants, with and without: 1) the root knot nematode Meloidogyne incognita, 2) the SPM Stratiolaelaps scimitus, and 3) the FLN Rhabditella axei in its culture medium. RESULTS: LT-SEM illustrated nematode prey held between SPM palps with the labrum, corniculi and extended chelicera ready to feed. As anticipated, gall abundance was lowest in the combined treatment of FLN and SPM. Not anticipated was that similar reduction in gall abundance occurred when only SPM or only FLNCM was added to the soil mix. Additionally, in the FLNCM treatment, foliar macronutrients N and K were significantly higher than the negative control. CONCLUSION: Our original aim was to use FLN as a supplementary food source for SPM in conservation IPM. Based on the significant reduction in gall numbers, and the increase in foliar macronutrients, it is clear that the FLNCM treatment play additional roles. What can be attributed to FLN and what can be assigned to the bacteria in the culture medium remains to be elucidated in future research.