The tomato leafminer, Tuta absoluta (Meyrick) a key pest of tomato both in greenhouses and open-fields, has spread rapidly throughout Iran. The efficiency of native isolates of three species of entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora) was evaluated against the tomato leafminer, T. absoluta larvae (outside leaf and inside galleries), and pupae at various concentrations and times in laboratory conditions. Experiments were conducted at 25 ± 2ºC, 65 ± 5% RH, and 16L:8D h photoperiod. S. feltiae nematode caused the highest mortality for larvae outside the gallery (53.61%), followed by 45% mortality for larvae inside galleries, and lowest mortality for pupae (3.88%). The effect of infective juveniles (IJ) and exposure time (ET) on larval mortality in different treatments showed a significant (P< 0.01) relationship between IJ and ET and their interactions. Mortality of the T. absoluta larvae and pupae rose with more IJ and longer exposure time. The LC50 for, S. feltiae, S. carpocapsae and H. bacteriophora were 156.01, 225.13, and 317.66 IJs/ml for the second instar larvae of T. absoluta (outside the gallery), 296.31, 305.23 and 320.66 IJs/ml for inside gallery, respectively. Therefore, S. feltiae was a more effective species and can be suggested for complementary studies for finding a suitable biocontrol agent of the pest.

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.