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Artificial diets (ADs) facilitate cost-effective mass rearing of many natural enemies. A life table analysis was conducted to compare the performance of Neoseiulus barkeri Hughes reared on four ADs and its prey, Tetranychus urticae Koch and Aleuroglyphus ovatus (Troupeau). The ADs were enriched with Bombyx mori (L.) hemolymph (AD1), Artemia franciscana Kellogg cysts and B. mori hemolymph (AD2), A. franciscana cysts and Corcyra cephalonica (Stainton) eggs (AD3), and A. franciscana cysts and Musca domestica L. larvae (AD4). Although N. barkeri reared on the four ADs all survived to adults, they had significantly longer life cycles and lower fecundity than those reared on T. urticae and A. ovatus. N. barkeri reared on AD2 and AD3 had a significantly higher r value, and shorter mean generation time than those reared on AD1 and AD4. Among the four ADs, N. barkeri fecundity was the highest on AD3 and oviposition period was the shortest on AD2. Measurement of the nutrient compositions of T. urticae, A. ovatus and AD3 showed that saccharide content in AD3 was highest, while the total amino acids content in T. urticae and A. ovatus were 9.1% and 19.3% higher than that in AD3. Among the 33 detected fatty acids (FA), AD3 was highest in saturated and monounsaturated FA content, and in polyunsaturated FA between T. urticae and A. ovatus. These results may help improve the reproductive performance of N. barkeri on AD3, and optimized AD3 may be useful for mass rearing of this generalist predatory mites.

Cannibalism and intraguild predation (IGP) are two common interactions occurs in animal kingdom which influence their population structure and dynamics. Neoseiulus barkeri (Hughes) and Scolothrips takahashii (Priesner) are important natural enemies of citrus red mite Panonychus citri (McGregor). However, little was known about their interactions and how the availability of extraguild (EG) prey P. citri modulated their interactions. In this study, we determined incidences of cannibalism and intraguild predation of these two predators when different densities of extraguild prey P. citri were available. Our results showed that incidences of both cannibalism and IGP and were significantly reduced in the presence of the extraguild prey. The intraguild predation between N. barkeri and S. takahashii was bidirectional, but N. barkeri was a predominant intraguild predator over S. takahashii. The S. takahashii fed on immobile N. barkeri egg, and N. barkeri fed on inactive prepupa and pupa of S. takahashii, but the conspecifics seldom did. Our results indicated that the interactions of predators decreased significantly when prey was available. The predatory mite N. barkeri was a stronger interspecific competitor. The results of this study may be useful in developing effective biological control strategies against P. citri.

The quantitative analysis of microRNA is extremely important in biological research and clinical diagnosis due to the relationship between microRNA and disease. In this study, we reported a new assay for the rapid and simple detection of microRNA based on G-quadruplex and exonuclease III (ExoIII) dual signal amplification. We specifically designed two hairpins with G-quadruplex sequence. In the absence of a target, the G-quadruplex sequences are enclosed in the hairpin and fluorescence signal shut down. However, when a target is added, the dual cycle is carried out because two hairpins are digested and X and Y sequences are released under the action of ExoIII. Then, these released sequences form the G-quadruplex sequence, and N-methylmorpholine (NMM) is embedded in the G-quadruplex to produce strong fluorescence. The linear range is from 2.5 × 10−10 to 4 × 10−9 mol L−1 with a low detection limit of 6 pM. Compared to some of the previous strategies, this bioassay needs only a simple one-step reaction, and is easy for realizing the rapid detection of microRNAs. The time required for the entire analysis is only 1 hour. In addition, this bioassay has good specificity and can be applied to the actual samples.

Organisms are always confronted with multiple stressors simultaneously. Combinations of stressors, rather than single stressor, may be more appropriate in evaluating the stress they experience. N. barkeri is one of predatory mite species that are commercialized for controlling spider mites. However, their biological control efficiency was often reduced because of high temperature and desiccation in summer. To understand how to improve the tolerance of N. barkeri to combined heat and desiccation stress, we pre-exposed the adult female of N. barkeri to high temperature, desiccation and high temperature &times, desiccation stress for acclimation. After proper recovery time, mites were subjected to high temperature &times, desiccation stress again to detect the acclimation effects. The results are as follows: (1) No decrease in mortality rate were observed under high temperature &times, desiccation stress after heat acclimation. Instead, it increased significantly with acclimation temperature and time. (2) Dehydration acclimation both at 25 &deg, C and high temperatures reduced mortality rate under high temperature &times, desiccation stress. Mortality rate was only significantly correlated with the amount of water loss, but not with temperature or water loss rate in acclimation, suggesting the increased tolerance is related to dehydration stress rather than heat stress. Among all acclimations, chronic dehydration at 25 &deg, C, 50% relative humidity were the most effective treatment. This study indicated dehydration acclimation is effective to enhance tolerance of N. barkeri to combined heat and desiccation stress, which can improve the efficiency of biological control under multiple stressors.

Organisms are always confronted with multiple stressors simultaneously. Combinations of stressors, rather than single stressor, may be more appropriate in evaluating the stress they experience. N. barkeri is one of predatory mite species that are commercialized for controlling spider mites. However, their biological control efficiency was often reduced because of high temperature and desiccation in summer. To understand how to improve the tolerance of N. barkeri to combined heat and desiccation stress, we pre-exposed the adult female of N. barkeri to high temperature, desiccation and high temperature × desiccation stress for acclimation. After proper recovery time, mites were subjected to high temperature × desiccation stress again to detect the acclimation effects. The results are as follows: (1) No decrease in mortality rate were observed under high temperature × desiccation stress after heat acclimation. Instead, it increased significantly with acclimation temperature and time. (2) Dehydration acclimation both at 25 °C and high temperatures reduced mortality rate under high temperature × desiccation stress. Mortality rate was only significantly correlated with the amount of water loss, but not with temperature or water loss rate in acclimation, suggesting the increased tolerance is related to dehydration stress rather than heat stress. Among all acclimations, chronic dehydration at 25 °C, 50% relative humidity were the most effective treatment. This study indicated dehydration acclimation is effective to enhance tolerance of N. barkeri to combined heat and desiccation stress, which can improve the efficiency of biological control under multiple stressors.

The predatory mite Neoseiulus barkeri (Hughes) is a good biological control agent for many small sucking pests. We aimed to determine whether rearing long term on alternative prey versus target prey species affected the performance of N. barkeri. Therefore, we investigated the prey preference, life tables, and population parameters of N. barkeri between alternative prey Tyrophagus putrescentiae (Schrank) and three species of spider mites, Tetranychus urticae Koch, Panonychus citri (McGregor), and Eotetranychus kankitus Ehara. We found that N. barkeri preferred the tetranychid mites to the alternative prey. Between the tetranychid mites, the predator consumed more P. citri and E. kankitus than T. urticae. When reared on T. urticae, the total developmental time and longevity of N. barkeri were the longest, whereas the intrinsic rate of increase was the lowest, indicating that the biotic fitness of predatory mite preyed on target of T. urticae was higher than on alternative prey of T. putrescentiae. However, total developmental time, longevity, and fecundity did not differ between N. barkeri reared on T. putrescentiae and P. citri, although these parameters were higher than those for mites reared on E. kankitus, indicating that the predatory mite reared on T. putrescentiae may not be affected to control P. citri, and that coexistence of P. citri and E. kankitus may enhance the control efficiency of N. barkeri. Altogether, our results demonstrated that long-term feeding on the alternative prey T. putrescentiae did not affect the performance of the predatory mite N. barkeri on various target spider mites.

Panonychus citri is a major pest mite that is of great economic importance in most citrus orchards in China. Utilizing native predatory natural enemies is one of the useful biological control strategies to maintain pest population below the level where damage occurs for an extended period of time. Although a handful of pesticides and predatory natural enemy species have proven effective on the integrated control of the citrus red mite, they are not hard-hitting tactics for control of the P. citri eggs due to the protection of egg-shell. This study evaluated the potential of a native species of philic egg-consumption predatory thrips, Scolothrips takahashii, for control of P. citri in southwestern Chinese citrus orchards. An age-stage, two sex life table of S. takahashii was constructed, showing this predatory thrips could develop and reproduce successfully when fed on all stages of P. citri. All the functional responses of S. takahashii adult males and females on different stages of P. citri fit the Holling II disc equation, whereas this predatory thrips preferred eggs of P. citri significantly more than their larvae or nymph. Mutual interference results indicated that the searching efficiency and predation rate of S. takahashii decreased significantly with increased predator densities when supplied with sufficient P. citri eggs. Overall, this study indicated the potential of S. takahashii as a biological control agent of P. citri and helped to characterize the role of native predatory thrips in pest mite management.

Eotetranychus kankitus Ehara (Acari: Tetranychidae) is an important pest in Chinese citrus orchards. In the present study, we aimed to evaluate the potential of Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae) for the biological control of E. kankitus. A two-sex life table of E. kankitus and N. barkeri was constructed to estimate development and fecundity. The functional response and stage-specific predation rate were analyzed to evaluate predation capacity. In addition, a timing model was used to project populations of E. kankitus with release of N. barkeri. Results showed that N. barkeri was able to develop and reproduce when fed on E. kankitus. The functional responses of N. barkeri on different stages of E. kankitus all fit the Holling II disc equation. When mixed stages of E. kankitus coexisted, N. barkeri mainly consumed larvae and nymphs. Based on the life tables and stage-specific predation rates, population projection revealed the stage structure and growth rate of N. barkeri on E. kankitus. Although E. kankitus had the higher growth rate, it was maintained at a low population level for several weeks after release of N. barkeri. The results highlighted the potential for utilizing N. barkeri as a biological control agent of E. kankitus.