Efficacy of three local isolates of entomopathogenic nematodes against the tomato leafminer, Tuta absoluta (Meyrick)

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.

Automated summary

The tomato leafminer, Tuta absoluta (Meyrick), a major pest of tomatoes in Iran, has rapidly spread. The effectiveness of three species of native entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora) against T. absoluta larvae and pupae was evaluated in the laboratory. S. feltiae had the highest mortality rate for larvae outside the gallery (53.61%), followed by larvae inside galleries (45%) and lowest mortality for pupae (3.88%). The study showed a significant relationship between nematode concentration, exposure time, and larval mortality. S. feltiae was found to be the most effective species and can be recommended for further biocontrol studies.