Resistance to spirodiclofen in Brevipalpus yothersi (Acari: Tenuipalpidae) from Brazilian citrus groves: detection, monitoring, and population performance

Abstract

BACKGROUND: Brevipalpus yothersi mite is the main vector of Citrus leprosis virus (CiLV), the causal agent of citrus leprosis disease. The acaricide spirodiclofen has been widely used to control this mite. However, failures in control using spirodiclofen have been frequently reported by citrus growers. In this study, we estimated the diagnostic concentration to monitor the resistance to spirodiclofen of B. yothersi populations collected in nine citrus groves in Brazil. We then selected the B. yothersi population that showed lowest mortality with the estimated diagnostic concentration of spirodiclofen to characterize the frequency of resistant individuals, as well as demographic and life table parameters.RESULTS: Variability was higher between populations in terms of susceptibility to spirodiclofen. The frequency of resistant eggs between populations ranged from 0.7% to 85.8%. The resistance ratio of B. yothersi to spirodiclofen was low to moderate. Survival rates of the immature stage, total adult longevity, oviposition days, and female fecundity were lower in the resistant strain. Furthermore, net reproduction rate, intrinsic rate of increase, finite rate of increase, and mean length of a generation were also lower in the R strain.CONCLUSION: Although variations in resistance to spirodiclofen were observed between populations, the resistance ratio was low to moderate. Such data can be useful in the development of resistance management strategies for B. yothersi in Brazilian citrus groves.

Impact of diseases and pests on premature fruit drop in sweet orange orchards in São Paulo state citrus belt, Brazil

“…24 The lack of rotation of different chemical groups of acaricides is contributing to reduce the efficacy of chemical control by selecting resistant populations of the vector. [49][50][51] Leprosis control is also undermined when the population of the mite vector grows above the action threshold. This happens due to deficient monitoring of the mite within the orchards as a result of a low frequency of inspections and use of an inappropriate sampling methodology, which mislead the detection of the initial population of the vector.…”

“…The longest periods of dry and hot weather, observed more frequently in the citrus belt, is certainly favoring the reproduction of the leprosis mite vector 24 . The lack of rotation of different chemical groups of acaricides is contributing to reduce the efficacy of chemical control by selecting resistant populations of the vector 49–51 . Leprosis control is also undermined when the population of the mite vector grows above the action threshold.…”

The importance of acaricides in the control of citrus leprosis mite and factors that interfere with the efficacy

“…A B. phoenicis dicofol-resistant strain showed lower fecundity and longevity than the susceptible strain (Alves, 1999). For spirodiclofen, there was a reduction in adult longevity, oviposition days, and fecundity in the resistant strain (Rocha et al, 2021). Furthermore, the resistance of the leprosis mite to hexythiazox was shown to be unstable under field conditions (Campos & Omoto, 2006).…”

“…Due to their satisfactory efficacy and control period, citrus growers have extensively used both acaricides. As a possible consequence of frequent use of these products, Rocha et al (2021) detected resistant acaricide. This compound proved to be highly effective in controlling adult females of B. yothersi due to its toxicity and repellent effect, despite not having an ovicidal effect (Andrade et al, 2019).…”

Spiro Derivatives in the Discovery of New Pesticides: A Research Review

“…Spirodiclofen research mainly focuses on drug resistance, acaricidal activity toward various mites, and its safety evaluation. − It has excellent acaricidal activity against mites, low residue concentrations, and desirable environmental characteristics. However, many pests exhibit high resistance to spirodiclofen, and they readily develop cross-resistance. , Research now focuses on the discovery of new spirodiclofen-derivative insecticides.…”