Evaluation of the Toxicity of Chemical and Biogenic Insecticides to Three Outbreaking Insects in Desert Steppes of Northern China.

The locusts Oedales asiaticus (Bey-Bienko) and Myrmeleotettix palpalis (Zubovski) (Orthoptera Acrididae) and the leaf beetle Galeruca daurica (Joannis) (Coleoptera, Chrysomelidae) are economically devastating insect species in the desert steppes of Northern China. Control is mainly and frequently dependent on highly toxic chemicals. To date, there have been no complete and comprehensive reports of insecticide applications to these key pests. In this study, laboratory bioassays were carried out to determine and compare the toxicity of twelve insecticides to three outbreaking insects, O. asiaticus, M. palpalis, and G. daurica, from three typical desert steppe regions, SZWQ, XHQ and WLTQQ, respectively. The responses of the two locust species and the leaf beetle were evaluated by topical application and leaf dip bioassay techniques across a range of concentrations to develop dosage-mortality regressions. The insecticides tested included six chemical insecticides (β-cypermethrin, imidacloprid, phoxim, λ-cyhalothrin, methomyl, chlorantraniliprole) and six biogenic insecticides (spinosad, avermectin, rotenone, matrine, azadiracthin, and methoxyfenozide). The results showed that phoxim, λ-cyhalothrin, β-cypermethrin and spinosad showed highly toxic activity to O.asiaticus, M. palpalis, and G. daurica, while methonyl, chlorantraniliprole, and rotenone were moderately toxic to both locust species and the leaf beetle. The LC(50) values of matrine, azadiractin, and avermectin were more than 1 μg a.i./adult for O. asiaticus and M. palpalis, the LC(50) values of which were higher 2 g/L for G. daurica. Our findings complement information from previous similar studies and will inform future studies relating to the control of outbreaking insects, such as O.asiaticus, M. palpalis, and G. daurica in desert steppes of northern China. This study is also expected to provide basic data on the use of chemical and biogenic insecticides for application in desert steppes.