Entomopathogenic Nematodes as Biocontrol Agents of the Tomato Leaf Miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) on tomato plants

The tomato leaf miner, Tuba absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) is an important pest of tomato crops in South America and it has recently been introduced to the Mediterranean area including Egypt. It is a devastative insect pest of tomato plantations. Susceptibility of T. absoluta larvae and pupae to the entomopathogenic nematode (EPNs) species; Steinernema monticolum and Heterorhabditis bacteriophora (HP88), was determined in both laboratory and field. Leaf bioassays were conducted in the laboratory to evaluate the nematode's efficacy in killing the insect larvae. H bacteriophora (HP88) killed 80% of the 4th instar larvae at 600 nematode-infective juveniles (IJs)/ml and 100% at 1200 IJs/ml 72 h post treatment. At the same time, when S. monticolum Us were used in the laboratory at 600 (IJs)/ml, 80 and 87% mortality was recorded on the 3rd and 4th instar larvae, respectively. Such mortalities were 84 and 89% at 1200 IJs/ml of S. monticolum, respectively. Field efficacy of the two tested nematode species after foliar application on tomato plants was evaluated. Total recorded mortality at H. bacteriophora varied along 3 consecutive years from around 60% in years 2011 and 2012 to 80% mortality in 2013. When S. monticolum was applied, mortality percent varied from 58 to 61% in years 2011 and 2012, respectively and reached a maximum of 67% in 2013. These results indicated that H. bacteriophora (HP88) was more virulent than S. monticolum against T. absoluta in the laboratory and in the field.