Assessing the Compatibility of Streptomyces saraceticus With Pesticides and the Efficacy in Controlling Root-Knot Nematode

Streptomyces saraceticus strain 31 (SS31) exhibits antagonistic activities against a variety of phytopathogenic bacteria, fungi and nematodes. In our effort to integrate SS31 into an effective pest management programme for controlling plant pathogens, we assessed the toxicities of 74 pesticides commonly employed in agricultural production on SS31 using paper disc assays. Most of the test insecticides, acaricides, nematicides and plant growth regulators showed no antagonistic effects towards SS31. However, all six tested herbicides, glyphosate, paraquat, glufosinate-ammonium, quizalofop-ethyl, pendimthalin and butralin exerted strong inhibitory effects on SS31. Among the 42 tested fungicides, half of them, including acid amides, strobilurins, carbamates, antibiotics and morphine displayed no detrimental effects on SS31. Notably, copper-based fungicides demonstrated high toxicity to SS31. Although chlorothalonil and thiophanate methyl + streptomycin displayed inhibitory effects on SS31, applying these pesticides with SS31 in pot tests resulted in a lower Meloidogyne incognita galling index compared with the mock control under greenhouse conditions. Additionally, applying SS31 with carbofuran or ethoprop effectively controlled M. incognita. These findings can provide strategies to refine application timing and enhance the beneficial effects of SS31.