Biosafety assessment of insecticides and chemicals used in citrus orchards: Impacts on the predatory beetle Cryptolaemus montrouzieri

Abstract

Citrus orchards frequently depend on various chemical treatments to manage pests and enhance tree growth and fruit quality. However, these chemicals can pose risks to natural enemies and environmental health. Therefore, it is crucial to select chemicals that effectively target pests while minimizing harm to natural enemies and promoting plant growth. To address this, we evaluated the acute toxicity of twenty-two chemical compounds commonly used in citrus farming on the citrus mealybug predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae). The tested chemicals were categorized into insecticides, acaricides, mineral oils, plant growth regulators, and mixtures of plant growth regulators and fertilizers. We assessed adult C. montrouzieri mortality using three bioassays: (i) direct spray application, (ii) contact with pesticide residues on foliage, and (iii) consumption of contaminated food, following the International Organization for Biological Control (IOBC) standards. The results revealed that the insecticide Tau-Fluvalinate exhibited some toxicity to adults across all bioassays. Sulfoxaflor showed slight toxicity when sprayed directly and consumed, while its residue primarily affected males. Acaricide Abamectin, with or without Levanola oil, posed risks, particularly to females in direct spray application. Notably, the consumption of the fertilizer Bonus (potassium nitrate), with or without plant growth regulators, caused significant mortality, though the effect was classified as slightly harmful. Our findings highlight the need for caution when applying these chemicals, as they may negatively affect the population of this key biocontrol agent. In contrast, the majority of the tested substances were found to be compatible with C. montrouzieri, offering benefits for both pest management and citrus cultivation.