Impact of relative humidity and water availability on the life history of the predatory mite Amblyseius swirskii

Abstract

The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is currently used as an e cient biological control agent of thrips, white ies and spider mites, which are economically damaging pests of ornamental plants and vegetable crops grown in greenhouses and elds 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 adult longevity and fecundity were partially or completely eliminated when drinking water was available. For the life table parameters, the highest values of net reproductive rate (R 0) and intrinsic rate of natural increase (r) were achieved at the highest RH when drinking water was availabile. 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 in uential on r than food source or temperature.

Effect of Relative Humidity on the Population Dynamics of the Predator Amblyseius swirskii and Its Prey Carpoglyphus lactis in the Context of Slow-Release Sachets for Use in Biological Control in Greenhouses

“…The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is widely used worldwide for the control of small insects and mites that cause damage to crops [ 1 , 2 ]. This organism is successful because some species are omnivorous and can complete their biological cycle by feeding on pollen, which allows them to establish on the crop in a preventive manner and even develop in the absence or scarcity of pests [ 3 , 4 ].…”

“…The establishment of a population of predatory mites and their effectiveness in pest control will depend on the environmental conditions of the crop under field conditions [ 6 ]. Microclimatic conditions such as temperature and RH are crucial factors contributing to the survival of these phytoseiids [ 2 ] and influence the increase in their populations. Specifically, RH determines the viability of eggs and the developmental success of adults [ 6 ].…”

“…However, in the agroecosystems, large populations of phytoseiids are not frequently observed, suggesting that some natural factors affect their abundance in the field crops [ 1 ]. Therefore, an understanding of the effects of the parameters involved on the life cycle is necessary to evaluate the potential growth of the population of the species [ 2 ].…”

“…RH is one of the most important microclimatic factors that influences the biological parameters of mite populations [ 1 , 2 , 10 , 15 ], as it is crucial for their survival [ 1 , 2 ]. It directly affects the net reproduction rate and the intrinsic rate of natural increase for both A. swirskii and C. lactis along with other parameters that determine the population dynamics of predators [ 2 ]. In most phytoseiid mites, the egg stage is the most sensitive to dry conditions [ 1 , 10 ].…”

“…[ 1 ]. In this sense, a high RH may alleviate extreme conditions such as extremely hot temperatures and water scarcity [ 1 , 2 , 15 ]; in contrast, low RH may limit population growth at optimal temperatures, especially if the mite uses energy to balance hydration at the expense of reproduction [ 1 , 2 ].…”