Mite Populations Research Articles

Ovicidal Effect of the Ethanolic Extract of Moringa oleifera Leaf on Oligonychus punicae (Trombidiformes: Tetranychidae) Eggs1

Abstract Mexico is the leader in avocado (Persea americana Miller [Lauraceae]) production, with the United States being the principal consumer of avocados produced there. The avocado crop is susceptible to attacks by insect and mite pests, including the avocado brown mite, Oligonychus punicae (Hirst) (Acari: Tetranychidae), which is a serious economic pest of the crop in Mexico. This study evaluated the effects of different concentrations (0.1, 0.5, 1, 5, 10, 15, and 20% [v/v]) of the ethanolic extract from Moringa oleifera Lamarck (Moringaceae) leaves against O. punicae eggs and its residual effect on the density of larvae and nymphs emerging from treated eggs. Egg mortality ranged from 0.0 at the 0.1% concentration to 70.48% at the 20% concentration, compared with the control group. Egg mortality increased as extract concentrations increased. The density of larvae and nymphs that emerged from the treated eggs was significantly lower than the density in the control, indicating that both the number of living larvae and nymphs responded to extract concentration. Our results support the suggestion that the ethanolic extract of M. oleifera leaf has ovicidal and residual activity against O. punicae and can be incorporated into an integrated mite management program to control avocado brown mite populations. Further studies are needed to assess the efficiency and efficacy of M. oleifera extract against arthropod pests and natural enemies under greenhouse and field conditions.

Distribution and population dynamics of spider mite oligonychus indicus hirst on sorghum

A field experiment was carried out to study the population dynamics of sorghum mite (O. indicus) infesting sorghum and its relation with different biotic and abiotic variables during 2019 and 2020 at Navsari Agricultural University, Navsari, Gujarat. The results revealed that mite population starts to build up during 34th SMW with 0.38 and 0.46 mite/2?2 cm2 leaf area during kharif-2019 and 2020, respectively and continued till the crop maturity. Further, the population of mite increased gradually and reached to its peak in 42nd and 41st SMW i.e., 8.92 and 9.42 mites/2?2 cm2 leaf area during kharif-2019 and 2020, respectively. During both the year of study, the bottom leaf canopy of sorghum harboured maximum mite population. Based on pooled data, both natural enemies showed highly significantly positive relationship with sorghum mite population. The sorghum mite population exhibited highly significant positive relationship with maximum temperature while, it had a significant positive correlation with average temperature, while a nonsignificant negative correlation exist with minimum temperature. Further, the morning, evening and average relative humidity had significant negative relationship with O. indicus. The rainfall and rainy days had highly significant negative influence on the spider mite population, however, the sunshine hours showed significant positive relation with the population of sorghum mite.. KEYWORDS :Sorghum, Oligonychus indicus Hirst, biotic factors, predators

Evaluating a Reduction in Treatment Duration of Ivermectin Diet for Fur Mite (Radfordia affinis) Eradication in Mice.

Murine fur mites are commonly excluded in modern research animal programs, yet infestations continue to persist due to challenges in detection and control. Because all diagnostic methods and treatment options have limitations, programs must make many operational decisions when trying to eradicate these ectoparasites. The primary aim of this study was to assess various durations of treatment time with an ivermectin-compounded diet in eliminating Radfordia affinis in mice as determined by PCR testing and pelt examination. A shorter treatment duration would be highly advantageous as compared with the current regimen of 8 wk as it would minimize cost and time for animal management programs, impediments to research, and ivermectin drug effects on infested animals. Five experimental groups of R. affinis -positive mice received dietary ivermectin for 0, 2, 4, 6, or 8 wk. A fur mite-negative, naïve mouse was added to each group every 8 wk to perpetuate the infestation and amplify any remaining populations of fur mites. At 16 wk after the respective treatment end, PCR testing was performed for all treated groups in conjunction with the positive control group (no treatment). Visual examination of pelts for mites and eggs via direct microscopy was also performed at each time point. All treated mice were free of R. affinis at 16 wk after the end of treatment as confirmed by both PCR testing and pelt examination. These findings indicate that a dietary ivermectin treatment duration of as little as 2 wk is effective in eliminating R. affinis, making successful eradication initiatives more achievable.

Beyond the Surface: Understanding Demodex and Its Link to Blepharitis and Facial Dermatoses.

Demodex represents the most frequent ectoparasite found in humans. Although Demodex mites are considered commensals of human pilosebaceous units, an abnormally high mite density can cause several ocular and cutaneous symptoms and signs, sometimes to a severe degree. Both Demodex spp. (folliculorum and brevis) play a significant part in eye pathology and facial dermatoses. These mites have been related to blepharitis, ocular rosacea, meibomian gland dysfunction and various skin diseases, including rosacea, demodicosis and seborrheic dermatitis. Understanding the importance of Demodex in both eye and skin conditions is crucial for accurate diagnosis and appropriate management strategies, which may involve targeted treatments to control the mite population and reduce associated symptoms.

Varroa mite removal from whole honey bee colonies by powdered sugar dusting is enhanced by crowding and mechanical agitation of treated workers

The honey bee parasite, Varroa destructor, is susceptible to removal by dusting agents that physically interfere with its ability to cling to its phoretic hosts. Here we describe modifications to established powdered sugar dusting techniques that modestly increased mite separation from hosts and allowed for greater reductions in whole colony mite infestation rates. These modifications increased body-to-body contact through crowding and mechanical agitation to supplement dusting effects on mite removal. Adult workers were isolated in a screened sugar shake box outside the colony, dusted with powdered sugar, then carefully shaken and bounced in crowded piles for one minute to separate mites from their hosts. Whole colony powdered sugar shake treatments resulted on average in a 92% reduction in post-treatment mite infestation rates over three successive mite treatments. Our modifications provided effective mite control comparable to the miticide Apiguard (thymol) without discernable negative effects on colonies. Four months after treatment, powdered sugar shake treated colonies had relatively similar-sized adult worker and brood populations as Apiguard treated colonies and larger adult populations than controls. Colonies also maintained queens and reared relatively few queen cells across treatments. Further comparisons of method components revealed that mechanical agitation of crowded workers enhanced mite separation from hosts due to powdered sugar dusting. Mechanical agitation alone only modestly increased mite separation compared to controls; however, high levels of mite separation associated with sugar dusting increased with agitation. These modified methods provide a rapid if laborious technique for reducing mite populations without chemical residues from restricted miticides.

Within-plant distribution and rapid assessment of sugarcane rust mite population on sugarcane canopy

Sugarcane rust mite (SRM), Abacarus sacchari, has been recognized in Florida since 1983. However, no detection technique had been developed yet, whereas a reliable, effective, and efficient technique is important in a mite management practice. The purposes of this study were to determine the within-plant distribution and to develop a sampling technique for SRM. The study was carried out in sugarcane fields naturally infested with the mite population. The mite distribution was identified with the visual direct counting technique and the imprinting technique. Subsequently, the effectiveness and reliability of both techniques were evaluated. The results showed that the within-plant distribution of mite populations was more concentrated in the middle canopy than in the upper or lower canopies. Furthermore, the mite sampling of the middle portion of the leaf could represent the entire mite population on the plant. More importantly, the imprinting technique was reliable, especially when the third or fourth (+3 or +4) fully expanded leaf was taken as sample, resulting in relative variation (RV) as low as 12.9% and 12.4%, respectively; therefore, the imprinting technique is a promising technique for population monitoring programs.

Amitraz Resistance in French Varroa Mite Populations-More Complex Than a Single-Nucleotide Polymorphism.

Resistance against amitraz in Varroa mite populations has become a subject of interest in recent years due to the increasing reports of the reduced field efficacy of amitraz treatments, especially from some beekeepers in France and the United States. The loss of amitraz as a reliable tool to effectively reduce Varroa mite infestation in the field could severely worsen the position of beekeepers in the fight to keep Varroa infestation rates in their colonies at low levels. In this publication, we present data from French apiaries, collected in the years 2020 and 2021. These data include the field efficacy of an authorized amitraz-based Varroa treatment (Apivar® ,Véto-pharma, France) and the results of laboratory sensitivity assays of Varroa mites exposed to the reference LC90 concentration of amitraz. In addition, a total of 240 Varroa mites from Eastern, Central, and Southern regions in France that were previously classified as either "sensitive" or "resistant" to amitraz in a laboratory sensitivity assay were genotyped. The genetic analyses of mite samples are focused on the β-adrenergic-like octopamine receptor, which is considered as the main target site for amitraz in Varroa mites. Special attention was paid to a single-nucleotide polymorphism (SNP) at position 260 of the ORβ-2R-L gene that was previously associated to amitraz resistance in French Varroa mites, Varroa. Our findings confirm that amitraz resistance occurs in patches or "islands of resistance", with a less severe reduction in treatment efficacy compared to pyrethroid resistance or coumaphos resistance in Varroa mites. The results of our genetic analyses of Varroa mites call into question the hypothesis of the SNP at position 260 of the ORβ-2R-L gene being directly responsible for amitraz resistance development.

Transcriptomics of differences in thermal plasticity associated with selection for an exaggerated male sexual trait.

The information about the magnitude of differences in thermal plasticity both between and within populations, as well as identification of the underlying molecular mechanisms are key to understanding the evolution of thermal plasticity. In particular, genes underlying variation in the physiological response to temperature can provide raw material for selection acting on plastic traits. Using RNAseq, we investigate the transcriptional response to temperature in males and females from bulb mite populations selected for the increased frequency of one of two discrete male morphs (fighter- and scrambler-selected populations) that differ in relative fitness depending on temperature. We show that different mechanisms underlie the divergence in thermal response between fighter- and scrambler-selected populations at decreased vs. increased temperature. Temperature decrease to 18 °C was associated with higher transcriptomic plasticity of males with more elaborate armaments, as indicated by a significant selection-by-temperature interaction effect on the expression of 40 genes, 38 of which were upregulated in fighter-selected populations in response to temperature decrease. In response to 28 °C, no selection-by-temperature interaction in gene expression was detected. Hence, differences in phenotypic response to temperature increase likely depended on genes associated with their distinct morph-specific thermal tolerance. Selection of males also drove gene expression patterns in females. These patterns could be associated with temperature-dependent fitness differences between females from fighter- vs. scrambler-selected populations reported in previous studies. Our study shows that selection for divergent male sexually selected morphologies and behaviors has a potential to drive divergence in metabolic pathways underlying plastic response to temperature in both sexes.

Managing Dust Mite Oligonychus afrasiaticus (McGregor) (Acari: Tetranchidae) Infesting Date Palm Orchards By Using Lemongrass Extract and Nanosulfur

The dust mite Oligonychus afrasiaticus (McGregor 1939) (Acari: Tetranychidae) poses a significant threat to date palm Phoenix dactylifera L. productivity in Iraq. To address this issue, a field study was conducted in a private date palm orchard in Al-Zubair district, Basrah province, Iraq, to assess the efficacy of some treatments in controlling the dust mite population on date palm fruits. The treatments included lemongrass extract, nanosulfur, a combination of lemongrass extract and nanosulfur, liquid sulfur, and a distilled water as control treatment. Treatments were applied by spraying on leaves and fruits at three dates: five weeks, eight weeks, and eleven weeks after pollination. Dust mite mortality rates were measured at intervals of 1, 3, 5, and 7 days after treatment application. Results revealed that the second date, eight weeks after pollination, exhibited the highest mortality rate of 76.77%, significantly outperforming other dates. Among the treatments, liquid sulfur showed the highest efficiency, with an 87.83% mortality rate, followed closely by the combination of lemongrass extract and nanosulfur (84.14%). Nanosulfur alone recorded a mortality rate of 79.26%, while lemongrass extract alone showed a mortality rate of 49.15%. The mortality rate increased over time, reaching 80.79% after 7 days and 65.76% after 1 day. In conclusion, liquid sulfur emerged as the most effective treatment for controlling the dust mite population on date palm fruits. The second date, eight weeks after pollination, was the optimal time for treatment application. These findings offer valuable insights into sustainable and environmentally friendly pest control strategies for date palm cultivation in Iraq.

Indirect effects of plasma-activated water irrigation on Tetranychus urticae populations

AbstractPlasma-activated water (PAW) is receiving increased attention as a booster of seed germination and seedling vigor, and some studies have described use of PAW to manage crop pathogens. Here, we examined physicochemical properties of two PAWs (referred to as PAW 6.0 and 9.4 min with atmospheric plasma jet) and assessed “their indirect effects” (applied as supplementary irrigation) on host suitability of tomato plants (Solanum lycopersicum L.) to two-spotted spider mites (Tetranychus urticae Koch). Exposure of water to cold plasma significantly lowered pH and increased concentrations of H2O2, NO2−, and NO3−. Supplementary PAW irrigations elicited significant increases in leaf composition of several elements (N, P, K S, Ca, and Mg), leaf reflectance, plant size, and trichome densities (except non-glandular trichomes on the adaxial surface). Preference bioassays revealed significant avoidance of settling and reduced oviposition by two-spotted spider mites on leaf discs from PAW-irrigated plants compared to those from untreated control plants. Performance bioassays showed a significant decrease in two-spotted spider mite populations on PAW-irrigated plants. Results presented in this study provide comprehensive support to the hypothesis that indirect effects of supplementary PAW irrigation significantly reduce host plant suitability to two-spotted spider mites. PAW 6.0 may be slightly better than PAW 9.4, and this difference in performance is discussed in this study. Applications of PAW as supplementary irrigation are likely highly compatible with other IPM tactics and should be considered an innovative and sustainable component in twenty-first-century pest management.

Efficacy of Insecticidal Spray Schedules Against Sucking Insect Pests on Chilli

A field experiment was conducted at the research farm, Agricultural Research Station, Department of Entomology, College of Agriculture, Ummedganj, Agriculture University, Kota during rabi 2020- 21. Bioefficacy of selected insecticides was evaluated against sucking insect pests viz., aphid (Aphis gossypii Glover), whitefly (Bemisia tabaci Gennadius) and mite (Polyphagotarsonemus latus Bank) on chilli (Capsicum annuum L.). This study revealed that, among the treatments tested, the combination of insecticides as per spray schedule, treatment T1 (acetamiprid 20 SP @ 100 g/ ha + ethion 50 EC @ 1500 ml/ ha followed by imidacloprid 17.8 SL @ 125 ml/ ha + propargite 57 EC @ 1500 ml/ ha followed by buprofezin 25 SC @ 300 ml/ ha + fenazaquine 10 EC @ 1250 ml/ ha followed by fipronil 5 SC @ 1000 ml/ ha + spiromesifen 240 SC @ 400 ml/ha followed by chlorantraniliprole 18.5 SC @ 150 ml/ ha) was found significantly most effective against aphid, whitefly and mite population up to 15 days after treatment.

Effects of natural treatments on the varroa mite infestation levels and overall health of honey bee (Apis mellifera) colonies.

The survival of the honey bee (Apis mellifera), which has a crucial role in pollination and ecosystem maintenance, is threatened by many pathogens, including parasites, bacteria, fungi and viruses. The ectoparasite Varroa destructor is considered the major cause of the worldwide decline in honey bee colony health. Although several synthetic acaricides are available to control Varroa infestations, resistant mites and side effects on bees have been documented. The development of natural alternatives for mite control is therefore encouraged. The study aims at exploring the effects of cinnamon and oregano essential oils (EOs) and of a mixed fruit cocktail juice on mite infestation levels and bee colony health. A multi-method study including hive inspection, mite count, molecular detection of fungal, bacterial and viral pathogens, analysis of defensin-1, hymenoptaecin and vitellogenin immune gene expression, colony density and honey production data, was conducted in a 20-hive experimental apiary. The colonies were divided into five groups: four treatment groups and one control group. The treatment groups were fed on a sugar syrup supplemented with cinnamon EO, oregano EO, a 1:1 mixture of both EOs, or a juice cocktail. An unsupplemented syrup was, instead, used to feed the control group. While V. destructor affected all the colonies throughout the study, no differences in mite infestation levels, population density and honey yield were observed between treatment and control groups. An overexpression of vitellogenin was instead found in all EO-treated groups, even though a significant difference was only found in the group treated with the 1:1 EO mixture. Viral (DWV, CBPV and BQCV), fungal (Nosema ceranae) and bacterial (Melissococcus plutonius) pathogens from both symptomatic and asymptomatic colonies were detected.

Evaluating the seasonal efficacy of commonly used chemical treatments on Varroa destructor (Mesostigmata: Varroidae)populationresurgence in honey bee colonies.

The purpose of this research was to determine how common chemical treatments influence Varroa destructor (Anderson and Trueman) populationresurgence rates (defined as time posttreatment for mite populations to reach 3 mites/100 adult bees) in managed honey bee (Apis mellifera L.) colonies seasonally. We conducted 2 experiments that followed the same basic protocol to address this purpose. We established 6 treatment groups in Experiment 1 in the fall of 2014: untreated control, Apivar, Apistan, CheckMite+, ApiLifeVar, and Mite Away II applied to 10 colonies per treatment. In Experiment 2, we applied 8 chemical treatments to each of 4 seasonal (spring, summer, fall, and winter) cohorts of honey bee colonies to determine how mite populations are influenced by the treatments. The treatments/formulations tested were Apivar, Apistan, Apiguard, MAQS, CheckMite+, oxalic acid (dribble), oxalic acid (shop towels), and amitraz (shop towels soaked in Bovitraz). In Experiment 1, Apivar and Mite Away II were able to delay V. destructor resurgence for 2 and 6 months, respectively. In Experiment 2, Apiguard, MAQS, oxalic acid (dribble), and Bovitraz treatments were effective at delaying V. destructor resurgence for at least 2 months during winter and spring. Only the Bovitraz and MAQS treatments were effective at controlling V. destructor in the summer and fall. Of the 2 amitraz-based treatments, the off-label Bovitraz treatment was the only treatment to reduce V. destructor populations in every season. The data gathered through this study allow for the refinement of treatment recommendations for V. destructor, especially regarding the seasonal efficacy of each miticide and the temporal efficacy posttreatment.

The efficacy of 1-allyloxy-4-propoxybenzene (3c{3,6}) against Varroa destructor mites in honey bee colonies from Maryland, USA.

Varroa destructor Oud (Acari: Varroidae) is a harmful ectoparasite of Apis mellifera L. honey bees causing widespread colony losses in Europe and North America. To control populations of these mites, beekeepers have an arsenal of different treatments, including both chemical and nonchemical options. However, nonchemical treatments can be labor intensive, and Varroa has gained resistance to some conventional pesticides, and the use of other chemical treatments is restricted temporally (e.g., cannot be applied during periods of honey production). Thus, beekeepers require additional treatment options for controlling mite populations. The compound 1-allyloxy-4-propoxybenzene (3c{3,6}) is a diether previously shown to be a strong feeding deterrent against Lepidopteran larvae and a repellent against mosquitoes and showed promise as a novel acaricide from laboratory and early field trials. Here we test the effect of the compound, applied at 8 g/brood box on wooden release devices, on honey bees and Varroa in field honey bee colonies located in Maryland, USA, and using a thymol-based commercial product as a positive control. 3c{3,6} had minimal effect on honey bee colonies, but more tests are needed to determine whether it affected egg production by queens. Against Varroa3c{3,6} had an estimated efficacy of 78.5%, while the positive control thymol product showed an efficacy of 91.3%. 3c{3,6} is still in the development stage, and the dose or application method needs to be revisited.

Quantitative identification and sensor sensitivity analysis in detection of odor volatile compounds emitted by scaly grain mites, Suidasia pontifica Oudemans.

In Thailand, the scaly grain mite, Suidasia pontifica Oudemans, impacts the feed industry by emitting a lemongrass-like odor in contaminated feed, reducing its palatability. This study focused on identifying volatile organic compounds (VOCs) associated with this odor in contaminated chicken feeds and ground maize, as well as individual mites using gas chromatography-mass spectrometry (GC-MS). We explored the relationship between VOC concentration and mite population size in chicken feed cultures, aiming to detect minimal mite presence through regression models. Additionally, we tested the sensitivity of nine electronic odor sensors in detecting these VOCs. Our results showed Z-citral and E-citral present in mite-contaminated ground maize, chicken feeds, but absent in uncontaminated samples. Mite populations in chicken feed followed a normal distribution, increasing rapidly, peaking, and then declining, a pattern mirrored in the concentrations of Z-citral and E-citral. Simple linear regression models confirmed a positive correlation between mite density and citral concentrations. Polynomial regression models indicated Z-citral is detectable at mite densities over 67 individuals per gram and E-citral over 3.89 individuals per gram. Odor sensors showed varying readings across different citral concentrations, uncontaminated, and mite-infested chicken feeds. Our study confirms that S. pontifica are responsible for the lemongrass-like odor in infested samples, due to Z-citral and E-citral. The citral concentrations increase with mite population growth and are detectable at low mite densities, suggesting their effectiveness as biomarkers for early mite infestation detection. Additionally, MQ series odor sensors detected these VOCs, indicating their potential for monitoring mite infestations in storage environments. © 2024 Society of Chemical Industry.

First report of established mite populations, Tropilaelaps mercedesae, in Europe

Ectoparasitic mites Tropilaelaps spp. (Mesostigmata: Laelapidae) can be devastating pests of Western honey bee, Apis mellifera L., colonies, but have so far occurred only in Asia. Here, we report for the first time on established populations in Europe. In 2021, high losses of honey bee colonies occurred in the Krasnodar region, Western Russia (53%) with clinical symptoms and mite morphology showing Tropilaelaps spp. infestations. We found that brood infestations fluctuated seasonally, and mites were able to overwinter locally. The specimens were identified as Tropilaelaps mercedesae using genetics. The source of pest invasion is yet unidentified, but it is very likely that T. mercedesae will further spread west and south. This calls for respective stakeholder action, especially in neighboring countries.

6Pgdh polymorphism in wild bulb mite populations: prevalence, environmental correlates and life history trade-offs

Genetic polymorphism in key metabolic genes plays a pivotal role in shaping phenotypes and adapting to varying environments. Polymorphism in the metabolic gene 6-phosphogluconate dehydrogenase (6Pgdh) in bulb mites, Rhizoglyphus robini is characterized by two alleles, S and F, that differ by a single amino acid substitution and correlate with male reproductive fitness. The S-bearing males demonstrate a reproductive advantage. Although the S allele rapidly fixes in laboratory settings, the persistence of polymorphic populations in the wild is noteworthy. This study examines the prevalence and stability of 6Pgdh polymorphism in natural populations across Poland, investigating potential environmental influences and seasonal variations. We found widespread 6Pgdh polymorphism in natural populations, with allele frequencies varying across locations and sampling dates but without clear geographical or seasonal clines. This widespread polymorphism and spatio-temporal variability may be attributed to population demography and gene flow between local populations. We found some correlation between soil properties, particularly cation content (Na, K, Ca, and Mg) and 6Pgdh allele frequencies, showcasing the connection between mite physiology and soil characteristics and highlighting the presence of environment-dependent balancing selection. We conducted experimental fitness assays to determine whether the allele providing the advantage in male–male competition has antagonistic effects on life-history traits and if these effects are temperature-dependent. We found that temperature does not differentially influence development time or juvenile survival in different 6Pgdh genotypes. This study reveals the relationship between genetic variation, environmental factors, and reproductive fitness in natural bulb mite populations, shedding light on the dynamic mechanisms governing 6Pgdh polymorphism.

Seasonal Incidence of <i>Tetranychus urticae</i> Koch on Brinjal under Protected Cultivation

The two-spotted spider mite Tetranychus urticae Koch is a key pest of many vegetable crops under protected cultivation. The seasonal incidence of two-spotted spider mite on brinjal in four seasons was studied under protected cultivation in 2020 and 2021. Two peaks were observed in mite population during the period of investigation. First peak was observed from mid-September i.e. during 38th and 39th SMW (5.4 to 5.6 mites/2 cm leaf area) to first fort night of October i.e. 40th, 41st and 42nd SMW (5.0 to 5.4 mites/2 cm leaf area), in 2020. Second peak was observed during April i.e. 15th, 17th and 18th SMW (5.0 to 5.8 mites/ 2 cm leaf area) to May i.e. 20th, 21st and 22nd SMW (5.0 to 6.0 mites/ 2 cm leaf area) in 2021. The multiple correlation coefficients between the population and abiotic factors were worked out from July 2020 to June 2021. The active stages were found significantly positively correlated with maximum temperature and non-significantly positively correlated with minimum temperature. The morning relative humidity was non-significantly negatively correlated with the population of eggs and significantly negatively correlated with active stages.

How do different agricultural managements interfere with the Phytoseiidae mite (Acari: Phytoseiidae) community in apple trees?

In this study we performed the sampling of phytoseiid mites in different apple production orchards, and we evaluated the richness and abundance of these mites, as well as their distribution in the different strata of the plants. Furthermore, we studied how the different apple tree cultivars affect the diversity and distribution of these predatory mites. Collections were carried out in apple orchards in three different production areas: 1- organic agriculture (Antônio Prado, RS); 2- conventional agriculture (Muitos Capões, RS); 3- regenerative agriculture (São Joaquim, SC). In total, seven orchards were evaluated, in Muitos Capões and São Joaquim, two orchards of the Fuji and Gala, whereas in Antônio Prado, three cultivars (Eva, Fuji and Gala) were considered. In each orchard, 40 plants were evaluated, and from each plant a median branch was randomly chosen from which a leaf was removed from the apical, median and basal thirds. The collected leaves were taken to the laboratory, they were observed and the mites found mounted in Hoyer's medium and identified. A total of 695 phytoseiid specimens were collected. Greater abundance was noted in the apical stratum of plants of the Gala cultivar, demonstrating the effect of cultivar and stratum on phytoseiid richness, abundance and distribution. Neoseiulus californicus (McGregor) (Phytoseiidae) was the main species in areas of conventional and regenerative cultivation, being present in all evaluated orchards, but with low occurrence in areas of organic management. In organic orchards, species of the genus Euseius [Euseius mesembrinus (Dean) and Euseius inouei (Ehara and Moraes)] (Phytoseiidae) were more abundant. The results suggest that producers consider less intensive use of pesticides and herbicides in orchards in order to maintain populations of predatory mites due to their potential for biological control.

Brevipalpus yothersiBaker (Tenuipalpidae) development in sweet orange plants is influenced by previous mite infestation and the presence of shelters.

Citrus leprosis is the most important viral disease affecting citrus. The disease is caused predominantly by CiLV-C and is transmitted by Brevipalpus yothersi Baker mites. This study brings some insight into the colonization of B. yothersi in citrus [(Citrus × sinensis (L.) Osbeck (Rutaceae)] previously infested by viruliferous or non-viruliferous B. yothersi. It also assesses the putative role of shelters on the behavior of B. yothersi. Expression of PR1 and PR4 genes, markers of plant defense mechanisms, were evaluated by RT-qPCR to correlate the role of the plant hormonal changes during the tri-trophic virus-mite-plant interplay. A previous infestation with either non-viruliferous and viruliferous mites positively influenced oviposition and the number of adult individuals in the resulting populations. Mite populations were higher on branches that had received a previous mite infestation than branches that did not. There was an increase in the expression of PR4, a marker gene in the jasmonic acid (JA) pathway, in the treatment with non-viruliferous mites, indicating a response from the plant to their feeding. Conversely, an induced expression of PR1, a marker gene in the salicylic acid (SA) pathway, was observed mainly in the treatment with viruliferous mites, which suggests the activation of a plant response against the pathogen. The earlier mite infestation, as well as the presence of leprosis lesions and a gypsum mixture as artificial shelters, all fostered the growth of the B. yothersi populations after the second infestation, regardless of the presence or absence of CiLV-C. Furthermore, it is suggested that B. yothersi feeding actually induces the JA pathway in plants. At the same time, the CiLV-C represses the JA pathway and induces the SA pathway, which benefits the mite vector.