Abstract
The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is currently used as an efficient biological control agent of thrips, whiteflies and spider mites, which are economically damaging pests of ornamental plants and vegetable crops grown in greenhouses and fields worldwide. Currently, the effects of relative humidity (RH) and water availability on the optimal growth of A. swirskii are unknown. Here, we test the combined effects of different levels of RH (33%, 53%, 73% and 92%) and water availability on the development and reproduction of male and female A. swirskii feeding on the dried fruit mite, Carpoglyphus lactis (Linnaeus). While eggs failed to hatch at 33% RH, the survival rates of the immature stages at ≥ 53% RH increased solely in response to water availability and not due to changes in RH. Regarding growth and development, low RH extended the egg–adult duration and pre-oviposition period. We also found that the negative effects of low RH on fecundity were partially or completely eliminated when drinking water was available. For the life table parameters, the highest values of net reproductive rate (R0) and intrinsic rate of natural increase (r) were achieved at the highest RH and when drinking water was available. Overall, water availability mitigated the negative effect of low RH on female reproduction, and female development was more sensitive to water availability than male development. Lastly, a comparison of similar research on A. swirskii suggested that water availability and RH are more influential on r than food source or temperature.
Highlights
The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is used worldwide as an effective biological control agent of whiteflies, thrips and spider mites on greenhouse crops such as sweet pepper, cucumber and ornamental plants (El-Laithy and Fouly 1992; Momen and El-Saway 1993; Messelink et al 2008; Kim et al 2009; Calvo et al 2011)
Eggs did not hatch at the lowest relative humidity (RH) (33%), this treatment was excluded from subsequent analyses
The development period of A. swirskii was influenced by RH, water availability and sex (Supplementary table S1)
Summary
The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is used worldwide as an effective biological control agent of whiteflies, thrips and spider mites on greenhouse crops such as sweet pepper, cucumber and ornamental plants (El-Laithy and Fouly 1992; Momen and El-Saway 1993; Messelink et al 2008; Kim et al 2009; Calvo et al 2011). It is important that A. swirskii successfully colonize the introduced area in order to control the target pest. Understanding the effects of climate on predatory mites helps to predict their suitability in a release area, and this is important for non-native species. The investigation of life history parameters is critical in evaluating the potential population growth of a species (Birch 1948). Since the initial discovery of A. swirskii, most studies have focused on aspects of its development and potential effects in biological control under a limited range of temperatures and RHs, apart from a single study of temperature-dependent life history parameters (Lee and Gillespie 2011)
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