DOI: https://doi.org/10.5513/JCEA01/23.3.3442

2022, 23 (3)   p. 632-641

Azin VAFA, Ayatollah SAEEDIZADEH

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 EPNs-positive 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 EPNs҆ population (%) in EPNs-positive samples. The lowest-highest incidence of EPNs҆ population was obtained as 15.52-33.4% in 7 EPNs-positive 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.

Keywords

steinernematidae, heterorhabditidae, natural occurrence, monitoring, environmental and soil factors

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