Comparative efficacy of new insecticide formulations against tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Tomato plants are the most important vegetable crop grown in Egypt.  Larvae of the tomato leafminer, Tuta absoluta, are the most important and destructive pest of tomato, capable of causing up to 100% of tomato yield loss in some regions.  Effectiveness of chemical control of T. absoluta is limited due to the insect's nature of damage as well as its rapid capability to develop resistance to diverse insecticides.  While biological pesticides against T. absoluta are still largely under development, a few synthetic pesticides have shown relative impact in decreasing field populations.  However, these synthetic pesticides are not offered at economically affordable cost to many farmers.  Two new formulations with more affordable cost, designed as Mash-T 15 EC and Mash-V 25 EC were prepared in our laboratory for control of T. absoluta.  Physiochemical properties were in accordance with the FAO/WHO specifications 2010.  We performed comparative efficacy tests against L2/L3 larvae using impregnated romaine lettuce leaves in leaf dipping bioassays under laboratory conditions.  We compared the new formulations to commonly used pesticides against T. absoluta, including Coragen® 20 SC (chlorantraniliprole), Avaunt® (Indoxacarb), and Emamectin benzoate® 5 WDG.  Results support that chlorantraniliprole was the most effective formulation against T. absoluta larvae, followed by Mash-V.  Mash-T and indoxacarb had moderate activity levels , but emamectin benzoate showed low levels of activity at affordable concentrations.  Statistical analyses did not detect any significant differences between chlorantraniliprole and Mash-V, or between indoxacarb and Mash-T.  However, significant differences were found between emamectin benzoate and other tested pesticides.  Our results support the use of either chlorantraniliprole or Mash-V individually or within a rotation to control T. absoluta and to delay resistance evolution.  The individual use of indoxacarb, Mash-T and emamectin benzoate is not recommended, but they may be used in programs to increase efficiency in controlling T. absoluta larvae.

Key Words: Tomato leafminer, Tuta absoluta, Bioassay, Efficiency, Insecticides