Populations of entomopathogenic nematodes in agricultural lands

Abstract

Entomopathogenic nematodes (EPNs) are known agents in pest biological control. Environmental factors can influence on populations of soil-inhabitant nematodes like EPNs in agricultural lands. In the current study, after selecting a suitable study site (33.20-33.42 N and 48-48.55 E), and soil sampling (250 samples) in May to July 2019, infectious juveniles of EPNs were extracted from soil samples according to the bait method. According to occurrence of EPNs-infected Galleria mellonella larvae, natural occurrence (%) of EPNs was estimated, while considering soil characteristics (salinity and acidity), region (altitude) and type of crop. Also, population incidence (%) of EPNs in EPNs-positive soil samples was estimated, according to G. mellonella larvae mortality by re-baiting. As results, seven soil samples were found to be EPNspositive per total samples. Natural occurrence (%) of EPNs, Steinernematidae and Heterorhabditidae was equal to 2.8, 2, and 0.8%, respectively. This was variable under ranges of area altitude, soil salinity and acidity, and crop type, so that the highest to lowest occurrence (%) of EPNs was observed in forage crops (4%), vegetables (4%), industrial crops (4%), fruit trees (2%), and cereals (1.33%), respectively. There was a significant difference (P<0.05) in incidence of EPNs ҆ population (%) in EPNs-positive samples. The lowest-highest incidence of EPNs ҆ population was obtained as 15.52-33.4% in 7 EPNspositive samples. As a conclusion, type of crop, altitude and soil acidity and salinity play a role in the level of occurrence and incidence of EPNs populations. These may have affected the biological and ecological properties of the nematodes populations.