Abstract
Chemical control is the main method for controlling the tomato leafminer, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae). Reported techniques for the evaluation of insecticide toxicity to the tomato leafminer are not in agreement with field conditions and do not allow us to verify whether doses used in the field are efficient for control. Thus, the objective of this work was to develop a bioassay methodology to study the toxicity of insecticide formulations to T. absoluta that represent field conditions for fast-acting insecticides (neurotoxics and inhibitors of respiration) and slow-acting insecticides (Bacillus thuringiensis and insect growth regulators). The leaf-dip method was the most efficient method for toxicity studies of insecticides formulations to T. absoluta. We verified that bioassays with fast-acting insecticides should be performed with glass Petri dishes containing one tomato foliole from the 4th leaf from the plant apex infested with 10 larvae of 3rd instar and these bioassays can last 48 hours. Conversely, bioassays with slow-acting insecticides should be performed with two-liter transparent PET bottles containing the 4th leaf from the plant apex, with their petioles immersed in a glass bottle containing 120 mL of water, and this leaf should be infested with 10 larvae of 2nd instar and this bioassays can last seven days.
Highlights
The tomato leafminer Tuta absoluta (MEYRICK, 1917) (Lepidoptera: Gelechiidae) originates from South America (GIORDANO; SILVA, 1999) and was recently introduced in Europe and North Africa (GARCIA; VERCHER, 2010)
The goal of this work was to develop a bioassay methodology to study the toxicity of insecticide formulations on T. absoluta that corresponds to field conditions for both fast-acting and slow-acting insecticides
The most efficient methodology to study the toxicity of insecticide formulations to T. absoluta is leafdip
Summary
The tomato leafminer Tuta absoluta (MEYRICK, 1917) (Lepidoptera: Gelechiidae) originates from South America (GIORDANO; SILVA, 1999) and was recently introduced in Europe and North Africa (GARCIA; VERCHER, 2010). This insect is a serious tomato pest, because its larvae mine the leaves and bore fruits and stems (PICANÇO et al, 1998 e 2007). The slow-acting insecticides are Bacillus thuringiensis toxins and insect growth regulators They usually kill larvae of early instars in at least five days (FISK; WRIGHT, 1992; SILVA et al, 2003)
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