Compatibility of early natural enemy introductions in commercial pepper and tomato greenhouses with repeated pesticide applications

Abstract

Successful integrated pest management in protected crops implies an evaluation of the compatibility of pesticides and natural enemies (NE), as control strategies that only rely on one tactic can fail when pest populations exceed NE activity or pests become resistant to pesticides. Nowadays in Almería (Spain), growers release NE prior to transplanting or early in the crop cycle to favor their settlement before pest arrival because this improves biocontrol efficacy, although it extends pesticide exposure periods. The purpose of this research was to evaluate the compatibility of two applications of pesticides with key NE in 2-year trials inside tomato and sweet pepper commercial greenhouses: Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), Orius laevigatus (Say) (Hemiptera: Anthocoridae) and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae). In tomato, flubendiamide and chlorantraniliprole (IOBC category 1) were compatible with N. tenuis, but chlorpyrifos-methyl and spinosad (IOBC categories 2-3), which effectively reduced Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) density, compromised its predatory activity. In sweet pepper, chlorantraniliprole (IOBC category 1) was the only pesticide compatible with O. laevigatus while chlorantraniliprole, emamectin benzoate, spirotetramat and pymetrozine were harmless (IOBC category 1) to Amblyseius swirskii, and sulfoxaflor slightly harmful (IOBC category 2) to this phytoseiid predator.

Keywords: Amblyseius swirskii; Nesidiocoris tenuis; Orius laevigatus; Tuta absoluta; chemical control; Frankliniella occidentalis.

Figure 1

Mean ± SEM population of Nesidiocoris tenuis and Tuta absoluta per leaf inside tomato commercial greenhouses in 2016 (A and C) and 2017 (B and D) after two pesticide applications on September 30 and October 11, 2016, and on October 11 and 21, 2017. Arrows point out the moment of pesticide applications. Different letters stand for statistical differences among treatments according to a Linear Mixed Model test using pesticide as the fixed factor and sampling dates as the repeated measures factor, followed by LSD pairwise comparisons (P < 0.05).