An impact assessment of insecticides application on the non-targeted mosquito Aedes albopictus (Skuse) in Punjab rice fields, Pakistan

Abstract

Insecticidal control of insect pests of rice crop may influence the environment and nontarget species in rice fields. Aedes albopictus, one of the most common nontarget species present in rice fields, received lethal and sublethal exposures to insecticides used in rice cultivated fields. The present work explores the effects of insecticides in six non-targeted Ae. albopictus strains collected from rice fields with a history of insecticidal usage in comparison with a laboratory susceptible reference strain (REF) and a strain (LHR) collected from a rice field with no, or minimal, history of insecticidal usage. Two types of effects, the resistance development and performance of biological traits, were studied by selecting seven commonly used insecticides in rice fields in Punjab, Pakistan. The results revealed that the strains collected from the rice fields with histories of insecticidal usage exhibited significant levels of resistance to flonicamid, chlorantraniliprole, gamma-cyhalothrin, fipronil, monomehypo, triazophos, and carbofuran, when compared with REF and LHR strains. In addition, Ae. albopictus strains revealed a significantly weaker performance of biological traits (rate of pupae formation, survival of male and female adults (except females of OKR and MTN strains), and ovipositing females) than those of the REF and LHR strains. However, the fecundity of all field strains was only significantly different with that of the REF strain. In conclusion, the results highlight the problem of the negative effects of insecticidal usage in rice fields on nontarget species present in the same environment, and emphasize the need to adopt pest management activities that are safe for the environment.

Keywords: Ecotoxicology; Fitness cost; Insecticide resistance; Risk assessment.

Figure 1. Collection areas of Aedes albopictus strains from major rice growing areas of Punjab, Pakistan (Wikimedia commons: https://commons.wikimedia.org/wiki/File:Pakistan_Punjab.png).

Figure 2. Percentage of larvae of different strains of Aedes albopictus converted to pupal stage (mean ± S.E.).

Figure 3. Survival rate (%) of male and female adults of different strains of Aedes albopictus (mean ± S.E.).

Figure 4. Rate of blood females (%) that deposited eggs, and fecundity (number of eggs per female) of different strains of Aedes albopictus (mean ± S.E).