Host plant-mediated bottom-up effects on the biology and demographic parameters of the predatory mite Amblyseius swirskii via the citrus red mite Panonychus citri.
TL;DR
Overall, tangerine is recommended as the most suitable citrus species for supporting A. swirskii populations in augmentative biological control programs, while the poor suitability of grapefruit should be considered when designing pest management strategies in citrus orchards.
Abstract
Bottom-up effects of plant-mediated tritrophic interactions on the biological and demographic parameters of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were investigated using the citrus red mite, Panonychus citri McGregor (Acari: Tetranychidae), as intermediary prey reared on five commercially important citrus species: tangerine, orange, sour orange, grapefruit, and lime. Cohort life table experiments were conducted under controlled conditions (25 ± 1 °C, 60 ± 5% RH, 16:8 h L: D), and demographic parameters were estimated using the age-stage, two-sex life table method. Results demonstrated that the citrus host plant species significantly influenced the developmental, reproductive, and population growth parameters of A. swirskii. The shortest and longest pre-adult developmental period was recorded on tangerine and grapefruit, respectively. Predators reared on prey originating from tangerine exhibited the most favorable biological performance, including the shortest pre-adult development, longest adult longevity, and highest population growth parameters (r = 0.199 day- 1; R0 = 21.81 females/female), whereas grapefruit consistently yielded the poorest predator performance (r = 0.163 day- 1; R0 = 12.78 females/female). Pearson's correlation analysis revealed significant negative correlations between predator performance parameters and leaf secondary metabolites (total phenolics, flavonoids, and anthocyanins), and positive correlations with primary metabolites (proteins and carbohydrates). Cluster analysis classified the five citrus species into three distinct clusters, with tangerine and grapefruit forming singleton clusters at opposite extremes of the suitability spectrum. These findings provide compelling evidence for prey-quality-mediated bottom-up trophic cascades in the Citrus-P. citri-A. swirskii system. Overall, tangerine is recommended as the most suitable citrus species for supporting A. swirskii populations in augmentative biological control programs, while the poor suitability of grapefruit should be considered when designing pest management strategies in citrus orchards. The identified correlations between leaf secondary metabolites and predator performance further highlight the pivotal role of plant biochemistry in shaping tritrophic interactions.