Acute Toxicity of Fresh and Aged Residues of Pesticides to the Parasitoid Tamarixia radiata and to the HLB-Bacteria Vector Diaphorina citri

Abstract

One method for controlling the Asian citrus psyllid (ACP) Diaphorina citri Kuwayama, the vector of the putative causal agent of Huanglongbing, uses the parasitoid Tamarixia radiata (Waterston). However, the general intensive use of insecticides has reduced the numbers of this parasitoid. This study evaluated the effect of the residual action of 24 insecticides on T. radiata and also determined the differential toxicity of insecticides to D. citri and T. radiata, using three bioassays. In the first, when adults of the parasitoid were exposed to residues of the 24 insecticides, ten were considered short-life (class 1), six slightly persistent (class 2), five moderately persistent (class 3), and three insecticides were considered persistent (class 4), under the IOBC/WPRS classification system. The second bioassay evaluated the sublethal concentrations of the persistent insecticides (formetanate, dimethoate, spinosad). Increasing the concentrations of the insecticides increased the number that were classified as persistent. In the third bioassay, evaluation of the differential toxicity of eight insecticides to the ACP and the parasitoid showed that chlorpyrifos and bifenthrin were more harmful to T. radiata. Therefore, these two insecticides are not recommended for application at the time of parasitoid release. Cypermethrin, imidacloprid, and dimethoate caused higher mortality of D. citri and are most often recommended in IPM programs. The choice of an insecticide for the control of citrus pests must be made with care, aiming to preserve the natural enemies in the ecosystem, and thereby contribute to the success of biological control.

Topical and field‐tested residual effects of globally used insecticides on the parasitoid Tamarixia radiata released against the Asian citrus psyllid, Diaphorina citri

“…Beloti et al. (2018) reported effects of imidacloprid on T. radiata through 15‐day‐old residues probably because treated plants were held under controlled environment in a glasshouse whereas residues in our study weathered under natural Florida conditions in the field. According to Florida automated weather network (FAWN) data, the average minimum and maximum temperatures during the present experiment in the field were 21.98 and 32.95 °C, with peaks of 20.30 and 35.56 °C, and 75–91% r.h.…”

Chemical and biological products used in sugarcane and their effect on Trichogramma galloi

“…The insecticidal molecule chlorantraniliprole, for example, has high control rates for D. saccharalis infestations (Silva et al, 2020), causing irregular contraction of muscle cells, leading to paralysis, lethargy, starvation, and death (Tohnishi et al, 2005). However, studies have demonstrated the negative effects of chemical insecticides on natural enemies, such as parasitoids used in sugarcane (Desneux et al, 2007; Goulart et al, 2012; Costa et al, 2014; Beloti et al, 2018; Matioli et al, 2019).…”