Use of predatory mirids for control of the tomato borer Tuta absoluta ( Meyrick) in Sardinian greenhouse tomatoes.

The introduction of Tuta absoluta in Sardinia ( Italy) has caused an important increase in the number of insecticide treatments applied for pest management on greenhouse tomatoes, thus raising growers' demand for alternative control options. To evaluate the efficacy of releasing two specimens of Macrolophus pygmaeus or Nesidiocoris tenuis per m2 for the control of tomato borer infestations, an investigation was conducted under field conditions between August 2010 and July 2011. The tests were carried out on 18 commercial greenhouse crops. Fifteen other greenhouses, where no biocontrol agents were released, were also surveyed as controls. The release of the mirid bugs resulted in poor population growth of predators, which reached a peak density of 1.79 individuals per plant. In approximately half of the cases, this was caused by the application of pesticides (usually abamectin and oxamyl) which are highly toxic to the predatory mirids. However, even in crops where only products regarded as harmless to beneficials were used (e.g. Bacillus thuringiensis-based insecticides), both M. pygmaeus and N. tenuis failed to achieve the levels necessary for effective pest control. Presumably factors other than pesticide-related mortality contributed significantly to delaying mirid population build-up. Further studies are necessary to evaluate the feasibility of improving the efficacy of releases of the predatory mirids by the implementation of measures that may contribute to enhancing the establishment of these beneficials on tomato crops. [ABSTRACT FROM AUTHOR]