The effects of spiromesifen on life history traits and population growth of two-spotted spider mite (Acari: Tetranychidae)

Abstract

Laboratory bioassays were conducted to evaluate the effects of spiromesifen on gross fecundity, gross fertility, net fertility and population growth of two-spotted spider mite (Tetranychus urticae Koch) after treatments with four acaricide concentrations: 180 mg/l, i.e. maximum recommended concentration for use in glasshouses against spider mites, 18, 1.8, and 0.18 mg/l, i.e. concentration discriminative for eggs and immatures in preliminary studies which produced 100% mortality of these stages. Quiescent female deutonymphs were treated in the first assay, and young pre-ovipositing females in the second and third, in which exposure lasted 6 h and 20 h, respectively. In the first assay, the 180, 18, and 1.8 mg/l concentrations significantly reduced gross fecundity (61-85%), gross fertility (64-87%) and net fertility (85-94%) of the surviving females. In the second one, only the highest concentration achieved a significant statistical reduction in gross fecundity (52%), gross fertility (67%) and net fertility (84%). In the third assay, fecundity and fertility reduction under the two highest concentrations was 98-99% and 93-98%, whereas it was 50-74% under the 1.8 mg/l concentration, and statistically different from control values. In all three trials, treatments with 180, 18, and 1.8 mg/l concentrations significantly reduced the instantaneous rate of increase. In the third assay, treatments with the two highest concentrations caused population decline. Sublethal activity of the 0.18 mg/l concentration was not found in any assay to be statistically significant. Sublethal effects of spiromesifen and its impact on T. urticae management are discussed.

The effects of spirotetramat on life history traits and population growth of Tetranychus urticae (Acari: Tetranychidae)

“…Also, significantly higher reduction percentages of fertility were registered in the second assay, as well as a more pronounced reduction of r i values, with population decline which was caused by higher concentrations of spirotetramat. Similar pattern was previously reported for spiromesifen (Marcic et al 2010a). …”

“…Moreover, the same symptomology of poisoning described previously for these two tetronic acid derivatives (Wachendorff et al 2002;Nauen et al 2005;Marcic 2007;van Pottelberge et al 2009;Marcic et al 2010a) was observed for spirotetramat, which points to the same mode of action of these three compounds on spider mites. Much stronger action of spirotetramat was registered on females treated at preovipositional period, compared to females treated at teleiochrysalis stage.…”

“…In the first case, 24 h after the treatment the production of viable eggs was complete, and in the other case only partially inhibited, with a faster recovery of fertility of treated females. Ability of T. urticae females to recover from intoxication after treatment was previously demonstrated for spirodiclofen (Nauen 2005;Marcic 2007;van Pottelberge et al 2009) and spiromesifen (Marcic et al 2010a). Fertility, longevity and population growth of T. urticae over 10 days after the treatment with spirotetramat were significantly reduced in a concentrationdependent manner.…”

“…Positive r i values indicate a growing population, negative r i values indicate a population in decline and r i = 0 indicates a stable population (Stark and Banks 2003). This approach has been used in other bioassays with spider mites (Stark et al 1997;Teodoro et al 2005;Kim et al 2006;Marcic et al 2010a). Calculated r i values were analysed by one-way ANOVA, and the means were separated by Duncan's test (a = 0.05).…”

“…Spirodiclofen and spiromesifen are highly toxic to eggs and immatures of spider mites (Acari: Tetranychidae), whereas their activity against adult females is slower, with strong reduction of fecundity and fertility. In addition, spiromesifen acts similarly on juvenile stages and females of whiteflies (Wachendorff et al 2002;Nauen et al 2005;Bretschneider et al 2007;Marcic 2007;van Pottelberge et al 2009;Marcic et al 2010a).…”