Evaluation of the predatory mite, Neoseiulus californicus, for spider mite control on greenhouse sweet pepper under hot arid field conditions

Demographic and predatory parameters of a thelytokous phytoseiid mite as a biocontrol agent for spider mites

BACKGROUND

The phytoseiid mite Neoseiulus agrestis (Karg) was recently collected from tetranychid-damaged maize plants in northwest China. The demographic parameters and functional response of N. agrestis were studied to evaluate its potential against spider mites.

RESULTS

Starting with the capture of a solitary female mite, a laboratory population of N. agrestis was successfully established over multiple generations without any males being found. The life table experiment confirmed that N. agrestis indeed reproduced through thelytokous parthenogenesis and exhibited high fitness levels in both development and reproduction on four different diets consisting of spider mites Tetranychus urticae Koch and T. truncatus Ehara, astigmatid mites Aleuroglyphus ovatus (Tropeau), and cattail pollen Typha sp. The predator that preyed on two natural prey species exhibited a higher intrinsic rate of increase (T. urticae: 0.2501 day-1; T. truncatus: 0.2464 day-1). The functional responses of N. agrestis to different immature stages of T. urticae showed significantly higher average consumption rates (24.56 prey day-1) for larvae compared to other stages. Logistic regression analysis revealed that N. agrestis displayed a type II functional response across all immature stages of T. urticae, with the consumption rate increasing as prey density increased, until reaching a peak and eventually stabilizing at the plateau.

CONCLUSION

The enhanced fitness of N. agrestis on both prey and pollen, along with its high consumption rate on tetranychid mites, highlights the potential of this thelytokous predator as a promising biocontrol agent and provides a novel approach for the management of spider mites in China. © 2025 Society of Chemical Industry.

Parental exposure to heat waves improves offspring reproductive investment in Tetranychus urticae (Acari: Tetranychidae), but not in its predator, Phytoseiulus persimilis (Acari: Phytoseiidae)

The more frequent and intense occurrence of heat waves is a challenge for arthropods because their unpredictable incidence requires fast adaptations by the exposed individuals. Phenotypic plasticity within and across generations might be a solution to cope with the detrimental effects of heat waves, especially for fast-developing, small arthropods with limited dispersal abilities. Therefore, we studied whether severe heat may affect the reproduction of a pest species, the spider mite Tetranychus urticae, and its counterpart, the predatory mite Phytoseiulus persimilis. Single offspring females with different parental thermal origins (reared under mild or extreme heat waves) of both species were exposed to mild or extreme heat waves on bean leaves over 10 days, and the oviposition, egg sizes, survival, and escape behavior of the females were evaluated daily. The total losses of predators mainly via escapers were very high compared to prey, which makes a separation between selective and plastic effects on shifted reproductive traits impossible. Predator females laid smaller eggs, while their consumption and oviposition rates were unaffected during extreme heat waves. In comparison, larger prey females fed more and produced more, but smaller, eggs due to within- and trans-generational effects. These advantages for the prey in comparison to its predator when exposed to extreme heat waves during the reproductive phase support the trophic sensitivity hypothesis: higher trophic levels (i.e., the predator) are more sensitive to thermal stress than lower trophic levels (i.e., the prey). Furthermore, the species-specific responses may reflect their lifestyles. The proactive and mobile predator should be selected for behavioral thermoregulation under heat waves via spatiotemporal avoidance of heat-exposed locations rather than relying on physiological adaptations in contrast to the more sessile prey. Whether these findings also influence predator-prey interactions and their population dynamics under heat waves remains an open question.

Berry species and crop management approaches affect species diversity and abundance of predatory mites (Acari: Phytoseiidae)

Berries comprise an economically important group of crops. Knowledge about their arthropod pests and biological control agents is important in the development of more efficient integrated pest management programs. Identification of potential biocontrol agents based solely on morphological attributes may be difficult and so molecular techniques should be incorporated. Here we studied the species diversity of predatory mites in the family Phytoseiidae, and how this diversity is affected by the berry species and crop management approaches, specifically pesticide application regimes. We sampled 15 orchards in the State of Michoacán, Mexico. Sites were selected based on berry species and pesticide regimes. Mite identification was achieved by combining morphological attributes and molecular techniques. Phytoseiidae diversity was compared amongst blackberry, raspberry and blueberry. Subsequently we studied the effect of berry species and pesticide regime on the abundance of the most prevalent phytoseiid species. We identified 11 species of phytoseiid mites. The greatest species diversity was found in raspberry, followed by blackberry and then blueberry. The most abundant species were Typhlodromalus peregrinus and Neoseiulus californicus. The abundance of T. peregrinus was significantly affected by pesticide application but not by berry species. In contrast, abundance of N. californicus was significantly affected by berry species but not by pesticide regime.

Tomato Cultivars Resistant or Susceptible to Spider Mites Differ in Their Biosynthesis and Metabolic Profile of the Monoterpenoid Pathway

The two-spotted spider mite (TSSM; Tetranychus urticae) is a ubiquitous polyphagous arthropod pest that has a major economic impact on the tomato (Solanum lycopersicum) industry. Tomato plants have evolved broad defense mechanisms regulated by the expression of defense genes, phytohormones, and secondary metabolites present constitutively and/or induced upon infestation. Although tomato defense mechanisms have been studied for more than three decades, only a few studies have compared domesticated cultivars' natural mite resistance at the molecular level. The main goal of our research was to reveal the molecular differences between two tomato cultivars with similar physical (trichome morphology and density) and agronomic traits (fruit size, shape, color, cluster architecture), but with contrasting TSSM susceptibility. A net house experiment indicated a mite-resistance difference between the cultivars, and a climate-controlled performance and oviposition bioassay supported these findings. A transcriptome analysis of the two cultivars after 3 days of TSSM infestation, revealed changes in the genes associated with primary and secondary metabolism, including salicylic acid and volatile biosynthesis (volatile benzenoid ester and monoterpenes). The Terpene synthase genes, TPS5, TPS7, and TPS19/20, encoding enzymes that synthesize the monoterpenes linalool, β-myrcene, limonene, and β-phellandrene were highly expressed in the resistant cultivar. The volatile profile of these cultivars upon mite infestation for 1, 3, 5, and 7 days, revealed substantial differences in monoterpenoid and phenylpropanoid volatiles, results consistent with the transcriptomic data. Comparing the metabolic changes that occurred in each cultivar and upon mite-infestation indicated that monoterpenes are the main metabolites that differ between cultivars (constitutive levels), while only minor changes occurred upon TSSM attack. To test the effect of these volatile variations on mites, we subjected both the TSSM and its corresponding predator, Phytoseiulus persimilis, to an olfactory choice bioassay. The predator mites were only significantly attracted to the TSSM pre-infested resistant cultivar and not to the susceptible cultivar, while the TSSM itself showed no preference. Overall, our findings revealed the contribution of constitutive and inducible levels of volatiles on mite performance. This study highlights monoterpenoids' function in plant resistance to pests and may inform the development of new resistant tomato cultivars.

Maternal effect determines drought resistance of eggs in the predatory mite Phytoseiulus persimilis

The ability of an organism to adapt to short-term environmental changes within its lifetime is of fundamental importance. This adaptation may occur through phenotypic plasticity. Insects and mites, in particular, are sensitive to changes in temperature and humidity, especially during the juvenile stages. We studied the role of phenotypic plasticity in the adaptation of eggs to different relative humidity conditions, in the predatory mite Phytoseiulus persimilis, used worldwide as a biological control agent of the spider mite Tetranychus urticae. The biocontrol efficacy of P. persimilis decreases under dry conditions, partly because P. persimilis eggs are sensitive to drought. We exposed P. persimilis adult females from two different strains to constant and variable humidity regimes and evaluated the hatching rate of their eggs in dry conditions, as well as the survival and oviposition rates of these females. Whereas the eggs laid by P. persimilis females exposed to constant high humidity did not survive in dry conditions, females exposed to constant low humidity started laying drought-resistant eggs after 24 h of exposure. Survival and oviposition rates of the females were affected by humidity: females laid fewer eggs under constant low humidity and had a shorter lifespan under constant high and constant low humidity. The humidity regimes tested had similar effects across the two P. persimilis strains. Our results demonstrate that transgenerational phenotypic plasticity, called maternal effect, allows P. persimilis females to prepare their offspring for dry conditions.

Response to Multiple Stressors: Enhanced Tolerance of Neoseiulus barkeri Hughes (Acari: Phytoseiidae) to Heat and Desiccation Stress through Acclimation

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.

Diurnal temperature variations affect development of a herbivorous arthropod pest and its predators

The impact of daily temperature variations on arthropod life history remains woefully understudied compared to the large body of research that has been carried out on the effects of constant temperatures. However, diurnal varying temperature regimes more commonly represent the environment in which most organisms thrive. Such varying temperature regimes have been demonstrated to substantially affect development and reproduction of ectothermic organisms, generally in accordance with Jensen’s inequality. In the present study we evaluated the impact of temperature alternations at 4 amplitudes (DTR0, +5, +10 and +15°C) on the developmental rate of the predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) and their natural prey, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). We have modelled their developmental rates as a function of temperature using both linear and nonlinear models. Diurnally alternating temperatures resulted in a faster development in the lower temperature range as compared to their corresponding mean constant temperatures, whereas the opposite was observed in the higher temperature range. Our results indicate that Jensen’s inequality does not suffice to fully explain the differences in developmental rates at constant and alternating temperatures, suggesting additional physiological responses play a role. It is concluded that diurnal temperature range should not be ignored and should be incorporated in predictive models on the phenology of arthropod pests and their natural enemies and their performance in biological control programmes.

Functional responses and prey-stage preferences of a predatory gall midge and two predacious mites with twospotted spider mites, Tetranychus urticae, as host

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest of vegetables and other economically important crops. This study evaluated the functional responses and prey-stage preferences of three species of predators, a predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae), and two predatory mite species, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and Amblyseius swirskii (AnthiasHenriot), with T. urticae as the host, under laboratory conditions. The results showed that F. acarisuga was highly effective and the two species of predacious mites were moderately effective in feeding on T. urticae eggs. Logistic regression analysis suggested Type II (convex) functional responses for all three species. However, based on the estimates of the handling time and the attacking rates, the three predators had different predation capacities. Among the three species, F. acarisuga had the highest predation on T. urticae. The maximum daily predation by a larval F. acarisuga was 50 eggs/day, followed by a female N. californicus (25.6 eggs/day) and a female A. swirskii (15.1 eggs/day). A female N. californicus produced more eggs than a female A. swirskii did when they both fed on T. urticae eggs. In addition, all three predator species had no preystage preference for either prey eggs or nymphs. The findings from this study could help select better biological control agents for effective control of T. urticae and other pests in vegetable productions.

Mites (Acari) as a factor in greenhouse management

This review discusses the economically important pest mites (Acari) of greenhouses, aspects of their biology, and the acarine predators that attack them as well as various insect pests. Greenhouse factors affect pest mites as well as their natural enemy populations and their interactions. Conversely, pest mites affect greenhouse management in terms of the chemical and biological methods required to control their populations. Structure affects heating, cooling, and light, which can be manipulated with suitable screens. Crops often select for pests and their mite enemies. Both groups may be affected in greenhouses by adding pollen and by a CO(2)-enriched atmosphere. These factors impact pest mite populations, the damage they cause, and the methods used to control them. The possibility of incipient evolution occurring in greenhouses, along with the benefits and consequences for pest control, is discussed.

Evaluation of dry-adapted strains of the predatory mite Neoseiulus californicus for spider mite control on cucumber, strawberry and pepper

The goal of this study was to evaluate spider mite control efficacy of two dry-adapted strains of Neoseiulus californicus. Performance of these strains were compared to a commercial strain of Phytoseiulus persimilis on whole cucumber, pepper and strawberry plants infested with Tetranychus urticae at 50 +/- 5% RH. Under these dry conditions predators' performance was very different on each host plant. On cucumber, spider mite suppression was not attained by any of the three predators, plants 'burnt out' within 4 weeks of spider mite infestation. On strawberry, all predators satisfactorily suppressed spider mites yet they differed in short term efficacy and persistence. Phytoseiulus persimilis suppressed the spider mites more rapidly than did the BOKU and SI N. californicus strains. Both N. californicus strains persisted longer than did P. persimilis. The BOKU strain was superior to SI in population density reached, efficacy in spider mite suppression and persistence. On pepper, in the first 2 weeks of the experiment the BOKU strain was similar to P. persimilis and more efficacious in spider mite suppression than strain SI. Four weeks into the experiment the efficacy of P. persimilis dropped dramatically and was inferior to the SI and BOKU strains. Overall, mean predator density was highest on plants harbouring the BOKU strain, lowest on plants with P. persimilis and intermediate on plants with the SI strain. Implications for biocontrol of spider mites using phytoseiid species under dry conditions are discussed.