Sublethal effects of fenpyroximate and pyridaben on two predatory mite species, Neoseiulus womersleyi and Phytoseiulus persimilis (Acari, Phytoseiidae)

Abstract

Laboratory bioassays were conducted to evaluate the sublethal effects of fenpyroximate and pyridaben on life-table parameters of two predatory mites species, Neoseiulus (= Amblyseius) womersleyi and Phytoseiulus persimilis. In these assays, young adult females were treated with three sublethal concentrations of each acaricide. The life-table parameters were calculated at each acaricide concentration, and compared using bootstrap procedures. For each acaricide, the LC(50) estimates for both species were similar, yet the two species exhibited completely different susceptibility when the population growth rate was used as the endpoint. Exposure to both acaricides reduced the net reproduction rate (R (o)) in a concentration-dependent manner and their EC(50)s were equivalent to less than LC(7). Two different scales of population-level endpoints were estimated to compare the total effect between the species and treatments: the first endpoint values were based on the net reproductive rate (fecundity λ) and the second endpoint values incorporated the mean egg hatchability into the net reproductive rate (vitality λ). The fecundity λ decreased in a concentration-dependent manner for both acaricide treatments, but the vitality λ decreased abruptly after treatment of N. womersleyi with pyridaben. The change in the patterns of λ revealed that the acaricide effects at the population level strongly depended on the life-history characteristics of the predatory mite species and the chemical mode of action. When the total effects of the two acaricides on N. womersleyi and P. persimilis were considered, fenpyroximate was found to be the most compatible acaricide for the augmentative release of N. womersleyi after treatment.

Laboratory assays on the effects of a novel acaricide, SYP-9625 on Tetranychus cinnabarinus (Boisduval) and its natural enemy, Neoseiulus californicus (McGregor)

“…The sublethal concentrations of SYP-9625 were chosen from the 24 h acute concentration-response relationship generated for adult females of T . cinnabarinus ( Table 1 ) [ 9 ]. The LC 50 of SYP-9625 on adult females and eggs were 0.466 μg/mL and 1.472μg/mL, respectively.…”

“…In previous studies, many species of natural enemies and pesticides have been tested so far to corroborate the combination of chemical and biological control agents under laboratory conditions [ 38 – 42 ]. Moreover, numerous studies have focused on the importance of sublethal effects of pesticides on predatory mites [ 3 , 9 , 33 ]. On one hand, this is the first report on both pest mites and the predatory mites of the new pesticide SYP-9625.…”

“…Based on the inter-population differences in the sensitivities of these natural enemies, Lima evaluated different acaricide toxicities against Neoseiulus barkeri (Hughes) and suggested that fenpyroximate and chlorfenapyr can be used together with the predatory mite application [ 4 , 8 ]. Recently, the sublethal effects of acaricides have been considered a more accurate approach to measure toxicity than direct contact toxicity [ 9 ]. Mollaloo investigated the effect of three lethal concentrations pyridaben on the developmental and reproductive parameters of Neoseiulus californicus (McGregor), which confirmed that the maneuverability about the combination of natural enemies such as phytoseiid predators with compatible acaricides is the key to decrease not only chemical applications but also the environmental hazards [ 10 ].…”

Indirect Effects of Pesticides on Natural Enemies

“…It was reported by [145] that the miticide fenpyroximate did not negatively affect prey consumption of Neoseiulus (=Amblyseius) womersleyi on twospotted spider mite (Tetranychus urticae) eggs compared to the miticide pyridaben. However, both miticides indirectly affected reproduction of N. womersleyi and P. persimilis females.…”

“…Miticides, similar to other pesticides, may demonstrate variability in regards to any indirect effects on natural enemies depending on the type of miticide and predatory mite species [145]. It was reported by [145] that the miticide fenpyroximate did not negatively affect prey consumption of Neoseiulus (=Amblyseius) womersleyi on twospotted spider mite (Tetranychus urticae) eggs compared to the miticide pyridaben.…”