Mortality of Tuta absoluta by sprayers deposit volume structure

Abstract

ABSTRACT: In the scientific toxicity evaluations of insecticides against larvae of Tuta absoluta (Tomato pinworm), a leaf coverage rate of 100 % or very close to this value is sought to guarantee the contact of the insect with the chemical product. However, deposition can change according to the different pesticide application methods used in field productions; consequently, interfering with pest control. From this perspective, this study evaluated the mortality of Tuta absoluta and the deposited volume dispersion on tomato leaflets as a function of droplet sizes and the method of chemical treatment with abamectin. For that purpose, an experiment was conducted in a randomized block design with five treatments and five replications. The treatments consisted of different chemical treatment methods: immersion, hydraulic spraying with three droplet sizes, and pneumatic spraying, in which the following parameters were evaluated: larval mortality, volume retained (deposition), surface density of active ingredient, droplet density, and coverage percentage. The different chemical treatments with abamectin provided larval mortality rates above 90%. Furthermore, the highest mortality values (98% and 95.9%) were associated; respectively, with the sprayings that provided the highest droplet densities: hydraulic spraying with average droplets (181 droplets cm-2) and pneumatic spraying with very fine droplets (256 droplets cm-2), the latter using an application volume 84% lower (80 L ha-1) than the lowest volume recommended by the manufacturer (500 L ha-1).