Mite Pests Research Articles

Acaricidal effect of the antimicrobial metabolite xenocoumacin 1 on spider mite control

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most harmful pests in many agroecosystems worldwide. To effectively manage this pest, there is an urgent need to develop novel bio-active acaricides that support integrated pest management strategies targeting T. urticae. In this study, we explored the acaricidal effects of xenocoumacin 1 (Xcn1) on T. urticae and its predator Neoseiulus californicus using the highly purified compound. Xcn1 was extracted and purified from the cell-free supernatant of the Xenorhabdus nematophila CB6 mutant constructed by the easy promoter activated compound identification (easyPACId) method. When the concentration of Xcn1 exceeded 100 μg mL−1, the survival rate of spider mite adults declined to below 40% and the fecundity was decreased by 80% at six days post-application. At concentrations of 25 and 50 μg mL−1, Xcn1 significantly impeded spider mite development by inhibiting the molt. However, neither concentration had any adverse effects on the survival or reproduction of the predatory mite N. californicus. The results from laboratory and semi-field experiments consistently demonstrated the effectiveness of the antimicrobial metabolite Xcn1 in controlling pest mites at both the molecular and physiological levels. Our study offers a promising possibility that combines the compatible biocontrol agents of Xcn1 and predatory mites for integrated pest mite control.

Updating integrated mite management fifty years later: comparing laboratory pesticide susceptibility of a "new" generalist predatory mite to a cornerstone specialist predator.

Historically, integrated mite management in Washington apple orchards has focused on the conservation of the predatory mite Galendromus occidentalis (Nesbitt) to reduce secondary pest mite pressure. However, pesticide use has changed to include more selective products, coinciding with a shift in the predatory mite community composition to include a new major predator, Amblydromella caudiglans (Schuster). There is evidence that A. caudiglans is more pesticide sensitive than G. occidentalis. Therefore, updates on pesticide selectivity recommendations are needed to conserve this "new" key predator. Using bioassays, we examined lethal (female mortality) and sublethal effects (fecundity, egg hatch, larval survival) of four fungicides and 11 insecticides on A. caudiglans, to determine if existing conservation recommendations can be applied to this predatory mite. Susceptibility was compared to prior research on G. occidentalis. Mancozeb was the least selective fungicide tested on A. caudiglans; it caused high acute toxicity and sublethal effects. Carbaryl was the least selective insecticide and caused 100% mortality. Captan was the most selective fungicide. Chlorantraniliprole and cyantraniliprole were the most selective insecticides and therefore least likely to disrupt biological control by A. caudiglans. Non-target effects on A. caudiglans and G. occidentalis were similar, but A. caudiglans experienced higher mortality to some broad-spectrum insecticides. All products tested had some non-target effects on A. caudiglans. However, A. caudiglans sensitivity to most tested pesticides was similar to G. occidentalis. In general, existing spray recommendations for conserving G. occidentalis can be adjusted slightly and applied to A. caudiglans conservation. This article is protected by copyright. All rights reserved.

The genome sequence of a spider mite, Tetranychus truncatus, provides insights into interspecific host range variation and the genetic basis of adaptation to a low-quality host plant.

The phytophagous mite Tetranychus truncatus is a serious pest in East Asia but has a relatively narrower host range than the pest mite Tetranychus urticae, which can feed on over 1200 plant species. Here, we generated a high-quality chromosomal level genome of T.truncatus and compared it with that of T.urticae, with an emphasis on the genes related to detoxification and chemoreception, to explore the genomic basis underlying the evolution of host range. We also conducted population genetics analyses (in 86 females from 10 populations) and host transfer experiments (in 4 populations) to investigate transcription changes following transfer to a low-quality host (Solanum melongena, eggplant), and we established possible connections between fitness on eggplant and genes related to detoxification and chemoreception. We found that T.truncatus has fewer genes related to detoxification, transport, and chemoreception than T.urticae, with a particularly strong reduction in gustatory receptor (GR) genes. We also found widespread transcriptional variation among T.truncatus populations, which varied in fitness on eggplant. We characterized selection on detoxification-related genes through ω values and found a negative correlation between expression levels and ω values. Based on the transcription results, as well as the fitness and genetic differences among populations, we identified genes potentially involved in adaptation to eggplant in T.truncatus. Our work provides a genomic resource for this pest mite and new insights into mechanisms underlying the adaptation of herbivorous mites to host plants.

The influence of Ahy1 strain of Acremonium hansfodii on functional response of Neoseiulus barkeri to Tetranychus urticae

The two spotted spider mite (TSSM) Tetranychus urticae is one of the most economically key mite pests of fields and greenhouse crops over the world. In order to clarify the control efficacy of Neoseiulus barkeri on Tetranychus urticae in the presence of entomopathogenic fungus (EPF) Acremonium hansfodii. This study was conducted to evaluate the control of combining N. barkeri with A. hansfodii against T. urticae. The results showed that the functional response of N. barkeri treated with Ahy1 strain to T. urticae was Holling type II equation. Among these, the highest predation number and the shortest attack time were obtained for the predator feeding on eggs, then followed by feeding on nymphs, female adults ranked as the lowest. That of N. barkeri to T. urticae treated with Ahy1 strain was also Holling type II equation. The predation capacity of N. barkeri on nymphs and female adults of T. urticae treated by Ahy1 strain increased with the increase of the concentration of Ahy1 strain, but that when feeding eggs had no significant difference. Therefore, the combination of EPF with N. barkeri on control of TSSM had synergistic effects, which will provide the guidance to carry out combined utilization of entomogenous fungi with predatory mites.

Prediction of major pest incidence in Jute crop based on weather variables using statistical and machine learning models: A case study from West Bengal

Jute crop cultivated in Cooch Behar suffers a substantial amount of physical and economical loss every year due to several major insect pest infestation such as Yellow Mite (Polyphagotarsonemus latus Banks) and Jute Semilooper (Anomis sabulifera Guen). Constructed seasonal plots reveal that for Yellow Mite pest incidence is maximum at 55 DAS, while for Jute Semi Looper it is at 45 DAS. Correlation analysis indicate that the weather parameters such as minimum temperature at current week, maximum RH at one week lag, minimum temperature, minimum and maximum RH at two week lag are significantly correlated with the incidence of Yellow Mite, while in case of Jute Semilooper maximum temperature, minimum and maximum RH at two week lag are significantly correlated. Different forecasting models like ARIMA, ARIMAX, SARIMA, SARIMAX and SVR have been fitted and validated using RMSE values. In case of Jute Semilooper, SARIMAX model is found to be the best fitted model followed by SVR and SARIMA. Similarly, for Yellow Mite ARIMAX model produces the least RMSE value followed by SVR and ARIMA. Following successful model validation, forecasting is done for the year 2022 using the best fitted models.

Incomplete reproductive barriers and genomic differentiation impact the spread of resistance mutations between green- and red-colour morphs of a cosmopolitan mite pest.

Pesticide resistance represents a clear and trackable case of adaptive evolution with a strong societal impact. Understanding the factors associated with the evolution and spread of resistance is imperative to develop sustainable crop management strategies. The two-spotted spider mite Tetranychus urticae, a major crop pest with worldwide distribution and a polyphagous lifestyle, has evolved resistance to most classes of pesticides. Tetranychus urticae exists as either a green- or a red-coloured morph. However, the extent of genetic divergence and reproductive compatibility vary across populations of these colour morphs, complicating their taxonomic resolution at the species level. Here, we studied patterns of genetic differentiation and barriers to gene flow within and between morphs of T. urticae in order to understand the factors that influence the spread of resistance mutations across its populations. We derived multiple iso-female lines from Tetranychus populations collected from agricultural crops. We generated genomic and morphological data, characterized their bacterial communities and performed controlled crosses. Despite morphological similarities, we found large genomic differentiation between the morphs. This pattern was reflected in the incomplete, but strong postzygotic incompatibility in crosses between colour morphs, while crosses within morphs from different geographical locations were largely compatible. In addition, our results suggest recent/on-going gene flow between green-coloured T. urticae and T. turkestani. By screening the sequences of 10 resistance genes, we found evidence for multiple independent origins and for single evolutionary origins of target-site resistance mutations. Our results indicate that target-site mutations mostly evolve independently in populations on different geographical locations, and that these mutations can spread due to incomplete barriers to gene flow within and between populations.

Herbicides Harm Key Orchard Predatory Mites.

The phytoseiid mites Galendromus occidentalis and Amblydromella caudiglans are critical for conservation biological control of pest mites in Washington State, U.S.A. apples. While the non-target effects of insecticides on phytoseiids are well described, research on herbicide effects is limited. Using laboratory bioassays, we examined lethal (female mortality) and sublethal (fecundity, egg hatch, larval survival) effects of seven herbicides and five adjuvants on A. caudiglans and G. occidentalis. The effects of mixing herbicides with recommended adjuvants were also tested to determine if the addition of an adjuvant increased herbicide toxicity. Glufosinate was the least selective herbicide tested, causing 100% mortality in both species. Paraquat caused 100% mortality in A. caudiglans and 56% mortality in G. occidentalis. Sublethal effects were significant for both species when exposed to oxyfluorfen. Adjuvants did not cause non-target effects in A. caudiglans. The non-ionic surfactant and methylated seed oil increased mortality and decreased reproduction in G. occidentalis. The high toxicity of glufosinate and paraquat for both predators is concerning; these are the primary "burn down" herbicide alternatives to glyphosate, which is decreasing in use due to consumer toxicity concerns. Field studies are needed to determine the extent to which herbicides disrupt orchard biological control, focusing on glufosinate, paraquat, and oxyfluorfen. Consumer preferences will need to be balanced with natural enemy conservation.

Evaluation of reflective groundcovers for pest and fruit quality management in commercial pear orchards

AbstractReflective groundcovers can improve crop yield and quality and deter pests by increasing light penetration into plant canopies. In pear (Pyrus communis L.) orchards, this could increase profitability and reduce reliance on insecticides to manage pear psylla (Cacopsylla pyricola [Foerster]). Two types of reflective groundcovers, metallized polyethylene film (metallized film) and white geotextile fabric (reflective fabric), are known to increase pear yield and quality, and metallized film was recently reported to suppress pear psylla. Here, we tested reflective fabric for pear psylla suppression at a research orchard in 2019, then we partnered with five pear orchard managers to test metallized film and reflective fabric for pear psylla suppression at five conventional commercial orchards in 2020 and one organic commercial orchard in 2021. There was evidence of pear psylla suppression by both metallized film and reflective fabric, but effects varied among reflective materials, pear psylla life stages, season and year of study. Reflective groundcovers did not affect fruit size, weight, sunburn or pest mite abundance, and they were compatible with pear psylla biocontrol. Low perceived benefit relative to cost was a barrier to continued trialling and adoption. Whereas orchardists in our study used reflective groundcovers in addition to normal pesticide regimes, previous research studies suggest that reflective groundcovers can profitably replace some insecticides. Future studies are needed to test the outcomes of replacing pesticides with reflective groundcovers in commercial orchards and understand under what circumstances they improve pear quality and yield.

Sublethal and transgenerational effects of pyridaben exposure on the fitness and gene expression of Panonychus citri.

Panonychus citri is a globally dominant citrus plant pest mite. Pesticide-induced population resurgence is a concern for mite control. Exposure to sublethal concentrations of pesticides has stimulated reproduction and outbreak risks in many pests. Pyridaben, a mitochondrial electron transport inhibitor, has been frequently used worldwide in mite control. In the study, sublethal and transgenerational effects of pyridaben exposure on Pyr_Rs (resistant) and Pyr_Control (susceptible) strains were systematically investigated in both exposed parental generation (F0 ) and unexposed offspring generations (F1 and F2 ) by evaluating life-table and physiological parameters. After exposure to pyridaben, the fecundity of both strains was significantly reduced in F0 generation while significantly induced in F1 generation. Interestingly, these effects also stimulated the fecundity of the F2 generation in Pyr_Control strain while no significant effects occurred for Pyr_Rs strain. The intrinsic rate of increase (r) and finite rate of increase (λ) were significantly decreased only in F1 generation of Pyr_Control strain after exposure treatment. Meanwhile, the population projection indicated a smaller population size in F1 generation of Pyr_Control strain while a population increase for Pyr_Rs strain after sublethal treatment. Subsequent detoxification enzyme assays indicated that only P450 activities in F0 generation were significantly activated by LC30 exposure to pyridaben in both strains. Significant downregulation of reproduction-related (Pc_Vg) genes was observed in the F0 generations of both strains. Significant upregulation of P450 (CYP4CL2) and PcVg of the F1 generation in both strains suggested the presence of delayed hormesis effects on the reproduction and developed tolerance to pyridaben, although the effects didn't last over a longer period (F2 generation). These results provide evidence for transgenerational hormesis effects of low concentrations of pyridaben exposure that may lead to population increase and resurgence risks of resistant-mites in natural settings by stimulating reproduction. This article is protected by copyright. All rights reserved.

Interrelation between the Number, Stages of the Pest Mite and Feeding Potential of Amblyseius multidentatus (Predatory Mite) at Different Durations

The feeding potential of Amblyseius multidentatus was studied against pest mites Tetranychus cinnabarinus and Eutetranychus orientalis (pest mites of crops). A. multidentatus had a clear-cut preference for T. cinnabarinus over E. orientalis (tcal 3.18) irrespective of the stage of egg, larva, nymph and adult. A. multidentatus preferred to consume eggs of T. cinnabarinus than to feed on E. orientalis eggs. The most preferred stage of T. cinnabarinus was larva (S=1.84), followed by adult and egg stages (S=1.62, S=1.57, respectively). Consumption of different stages of the pest with respect to number and duration showed a significant difference. Interaction between stage and duration showed no significant statistical difference with each other. Interaction between stage (S) and number (N) showed a significant difference (N=0.41. 0.87, 0.83).

옥살산을 이용한 꿀벌 안전성과 꿀벌응애류 방제 효율 평가

This study investigated the safety of oxalic acid (natural acaricide), on honeybee ( Apis mellifera) colonies and its acaricidal effects on honeybee pest mites (Varroa destructor and Tropilaelaps mercedesae). To determine the safety and acaricidal effects of oxalic acid, the impacts of oxalic acid was examined using different treatment methods (i) fumigation and (ii) dripping (trickling), and concentrations (0.7, 3, and 6%). For the fumigation, 1 g of oxalic acid was treated inside the beehive, and the experimental groups were divided by blocking the entrance of the beehive for different durations (1, 5, 10, and 15 min.). For the dripping, oxalic acid-sugar solutions with different concentrations (0.7, 3, and 6%) were prepared and applied to the beehive to measure safety and efficacy of oxalic acid. The safety of honeybees with oxalic acid treatment showed no significant differences between the experimental and control groups for both the fumigation and dripping methods, and had no significant impact on the honeybee colonies. The acaricidal effect of oxalic acid treatment was higher against V. destructor in all experimental groups compared to the control group in the fumigation method. In the dripping method, only the experimental groups with 3 and 6% concentrations showed significant differences and demonstrated acaricidal effects compared to the control group. For T. mercedesae , the low number of detected individuals resulted in no significant effects. Both treatment methods did not show any significant acaricidal effects on V. destructor and T. mercedesae, which exist inside the capped brood cells.

Elucidating the Effect of Temperature Stress on the Protein Content, Total Antioxidant Capacity, and Antioxidant Enzyme Activities in Tetranychus urticae (Acari: Tetranychidae).

Tetranychus urticae Koch is a worldwide agricultural pest mite that feeds on more than 1100 kinds of crops. The mite has developed a high level of tolerance to high temperatures, but the physiological mechanism underlying the outstanding adaptability of this pest to high temperatures remains unclear. To clarify the physiological mechanisms of T. urticae in response to short-term heat stress, four temperatures (36, 39, 42, and 45 °C) and three short-term heat durations (2, 4, and 6 h) were conducted to test the effects on protein content, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the total antioxidant capacity (T-AOC). The results showed that protein content, antioxidant enzyme activity, and T-AOC in T. urticae were significantly induced by heat stress. These results suggest that heat stress induces oxidative stress and that antioxidant enzymes play an important role in reducing oxidative damage in T. urticae. The data of this study will provide a basis for further research on the molecular mechanisms of thermostability and ecological adaptability of T. urticae.

Prey suitability and life table analysis of Amblyseius swirskii and Amblyseius aerialis (Parasitiformes: Phytoseiidae) on Panonychus citri (Acariformes: Tetranychidae) and Phyllocoptruta oleivora (Acariformes: Eriophyidae)

Phytoseiid mites are important predators of several pests including mites and are widely used in enclosed and open crop production systems. We evaluated two phytoseiid species, one that is commercially available (Amblyseius swirskii), and a species found in Florida citrus (A. aerialis), against pest mites Panonychus citri and Phyllocoptruta oleivora. These pests cause significant losses to citrus grown in traditional orchards and enclosed systems such as Citrus Under Protective Screen (CUPS). CUPS is a new undercover system being implemented to produce citrus free of Huanglongbing (HLB) disease and its vector psyllid. Development period, longevity, reproduction, and life table parameters of the two predatory mites were evaluated under laboratory conditions at 22 ± 2 °C and 60 ± 5% RH. Phyllocoptruta oleivora was not suitable for both predatory mites even to complete development through protonymph stage. When fed on P. citri, A. swirskii developed faster than A. aerialis, (8.9 vs. 10.2 days, respectively) and exhibited a shorter pre-oviposition period than A. aerialis (3.6 vs. 5.5 days, respectively) and a longer oviposition period (31.9 vs. 24.1 days, respectively). Fecundity and oviposition rate were also higher for A. swirskii than A. aerialis averaging 43.4 vs. 17.3 eggs/female, respectively, and 1.4 vs. 0.7 eggs/female/day, respectively. The positive effects of feeding on P. citri also improved several life table parameters of A. swirskii compared to A. aerialis. The intrinsic rate of increase, finite rate of increase, and net reproductive rate were all significantly higher for A. swirskii (1.173, 0.16, and 32.52, respectively) than A. aerialis (1.105, 0.10, and 10.71, respectively). Findings suggest that both predatory mites benefited from feeding on P. citri and will be useful for their production and implementation in citrus pest management particularly against P. citri.

Acarofauna associated with coconut fruits (Cocos nucifera L.) in a crop area from Pará state, Amazon, Brazil

Aceria guerreronis Keifer and Steneotarsonemus furcatus De Leon are phytophagous mites that attack coconut fruits. These mites establish their colonies under the bracts in the perianth where they feed, causing necrosis and a loss of fruit quality and commercial value. Phytoseiidae is considered the most important family for the control of pest mites. With 256 species documented, the Phytoseiid fauna in Brazil is highly diversified. They are distributed across all Brazilian biomes, including the Amazon, Caatinga, Cerrado, Pampa, Atlantic Forest, and Pantanal. Regardless of the fact that the Amazon biome occupies an estimated 49% of the Brazilian territory, its acarofauna remains unexplored. In this region, coconut is one of the most cultivated crops, although the variety of mites in this crop in the Amazon is yet unclear. This information is essential since there are potential predatory species that can play an important role in the biological control of coconut pests. Thus, the present study investigated the diversity and seasonality of mites in coconut fruits in the Eastern Amazon production region throughout the year. Data were collected monthly and analyzed to determine the diversity and seasonality. The faunistic indices were calculated using the program ANAFAU, and the abundance and diversity of phytoseiids were analyzed using the software EstimateS. As the fruit ages, the quantity of injured fruits increases. The mites collected belonged to the families: Oribatida (20), Rhodacaroidea (14), Eriophyidae (473,904), Phytoseiidae (147), Tarsonemidae (133), Ascidae (122), Bdellidae (110), Tydeidae (59), Cunaxidae (7), Eupodidae (7), Cheyletidae (5), Blattisociidae (4), and Cryptognathidae (1). Throughout the collection period, A. guerreronis and S. furcatus were detected on fruits with and without damage, with A. guerreronis being the most prevalent. Predatory mites of the Phytoseiidae family were sampled from 12 collections, totaling 147 specimens distributed across eight species. Amblyseius aerialis (Muma) was the predominant predator species. The peak population of A. guerreronis and S. furcatus occurred in different periods, although both species were sampled during periods of high precipitation, suggesting adaptation to the climatic conditions of the region. Temperature was strongly correlated with mites of the Phytoseiidae family. The occurrence of these mites was more common in months with higher temperatures. The mite A. aerialis was discovered in 12 evaluations, with a greater occurrence in October 2019 and August 2020. Understanding the diversity, abundance, and population fluctuations of pest mites and their natural enemies in coconut plants is critical for developing integrated pest management strategies.

Feeding Biology of Euseius pariyarensis (Santhosh, 2018) (Acari: Phytoseiidae) on Red Spider Mite Tetranychus neocaledonicus (Andre, 1933) Infesting Bauhinia acuminate L.

Euseius pariyarensis (Santhosh, 2018) is a predatory mite, found associated with the pest mite, Tetranychus neocaledonicus (Andre, 1933) which infest the leaves of Bauhinia acuminate L. To study the feeding potential, tests were carried out in the laboratory under 30+2oC, 65±10%RH conditions. Promising results were obtained and the following observations were made regarding its feeding activities. Maximum consumption of eggs of prey mite was exhibited by adult females. The mean consumption rate of predators followed the order that female > male > deutonymph > protonymph >larva, respectively.

Reproducing during Heat Waves: Influence of Juvenile and Adult Environment on Fecundity of a Pest Mite and Its Predator.

The thermal history of arthropod predators and their prey may affect their reproductive performance during heat waves. Thus, a matching juvenile and adult environment should be beneficial as it enables the individuals to acclimate to extreme conditions. Prey fecundity, however, is also affected by a second stressor, namely predation risk. Here, we assessed the impact of extreme and mild heat waves on the reproductive output of acclimated (juvenile and adult heat wave conditions are matching) and non-acclimated females of the biocontrol agent Phytoseiulus persimilis, a predatory mite, and its herbivorous prey, the two-spotted spider mite Tetranychus urticae, on bean leaves. Their escape and oviposition rates and egg sizes were recorded over 10 days. Additionally, ovipositing prey females were exposed to predator cues and heat waves. Acclimation changed the escape rates and egg sizes of both species, whereas fecundity was only influenced by the adult thermal environment via increased egg numbers under extreme heat waves. Acclimation reduced predator and prey escape rates, which were higher for the predator. Pooled over acclimation, both species deposited more but smaller eggs under extreme heat waves. Acclimation dampened this effect in prey eggs, whereas acclimation resulted in smaller female eggs of the predator. Prey deposited larger male and female eggs. Predator cues reduced prey oviposition, but the effect was small compared to the large increase gained under extreme heat waves. We argue that the success of predators in controlling spider mites during heat waves mainly depends on the fates of escaping predators. A permanent absence of predators may result in the numerical dominance of prey.

Natural occurrence of Metarhizium in agricultural avocado soils (Persea americana Mill.) in Colima, Mexico

Avocado (Persea americana Mill.) has become one of the most important fruits in the world, being Mexico the main producer and exporter worldwide, it has led to an accelerated growth in the establishment of monoculture avocado plantations, promoting the increase of insect and mite pests, which has led to the need for biological control strategies for integrated pest management. The objective of this study was to isolate entomopathogenic fungi from the soil of a conventional avocado orchard and identify them by translation elongation factor 1-α (5’TEF). During the sampling, a total of 34 isolates were obtained, belonging to the genus Metarhizium, 23 isolates identified as Metarhizium robertsii and 11 as Metarhizium guizhouense. These results show the low diversity of entomopathogenic fungi species associated with the rhizosphere of the avocado crop and suggest that their occurrence could be associated with their ability to survive agronomic practices that induce their endophytic activity. It is necessary to understand the role of Metarhizium in the rhizosphere, this will allow the development of biological control programs specific for each crop, and thus guarantee its success in pest control.

From laboratory to field: laboratory-measured pesticide resistance reflects outcomes of field-based control in the redlegged earth mite, Halotydeus destructor

Resistance to pesticides is typically identified via laboratory bioassays after field control failures are observed, but the results of such assays are rarely validated through experiments under field conditions. Such validation is particularly important when only a low-to-moderate level of resistance is detected in the laboratory. Here we undertake such a validation for organophosphate resistance in the agricultural pest mite Halotydeus destructor, in which low-to-moderate levels of resistance to organophosphorus pesticides have evolved in Australia. Using data from laboratory bioassays, we show that resistance to the organophosphate chlorpyrifos is higher (around 100-fold) than resistance to another organophosphate, omethoate (around 7-fold). In field trials, both these chemicals were found to effectively control pesticide-susceptible populations of H. destructor. However, when applied to a resistant mite population in the field, the effectiveness of chlorpyrifos was substantially decreased. In contrast, omethoate remained effective when tested alone or as a mixture with chlorpyrifos. We also show that two novel (non-pesticide) treatments, molasses and wood vinegar, are ineffective in controlling H. destructor when sprayed to pasture fields at rates of 4 L/ha. These findings suggest a close link between levels of resistance quantified through laboratory bioassays and the field effectiveness of pesticides; however, in the case of H. destructor, this does not necessarily mean all field populations possessing organophosphate resistance will respond similarly given the potentially complex nature of the underlying resistance mechanism(s).

Presence of symptoms caused by parasitic species described in grapevine herbaria from Georgia, Spain and the United Kingdom

The present paper focuses on the presence of symptoms caused by parasitic species in samples of Eurasian grapevine (Vitis vinifera L.) belonging to different herbaria from , and the . In the Spanish case herbaria were collected by Clemente at the beginning of the 19th century and preserved at the Royal Botanical Garden of Madrid. This material was used as the basis for the publication in 1807 of the famous book “Ensayo sobre las variedades de la vid común que vegetan en Andalucía” (Essay on the varieties of common grapevine that vegetate in ). The Georgian herbaria originated from three institutions: National Museum of Georgia, National Herbarium of Georgia and . The time period of the Georgian herbaria dates from mid-19th century. The herbaria came from Kew Royal Botanical Gardens and contain samples dated as of 1843. According to observations, in the Spanish herbarium, 98 samples out of 185 show erinea, symptoms caused by Colomerus vitis (Pagenstecher) (Acari, Eryophiidae), from a total of 185 samples there. Meanwhile in other herbaria its presence was detected in 3 samples, which also showed spots caused by powdery mildew, Erysiphe necator (Schweinitz). Symptoms caused by downy mildew, Plasmopara viticola Berl. & De Toni, were only detected in one sample collected in . Results attest the frequent presence of this monophagous mite pest on Southern Spanish cultivars and wild exemplars for more than two centuries.

Different maize varieties have greater impact on Tetranychus urticae (Acari: Tetranychidae) than GE maize expressing Cry3Bb1 insecticidal protein

Genetically engineered (GE) maize expressing Bacillus thuringiensis Cry3Bb1 protein was developed to control Diabrotica spp. (Coleoptera: Chrysomelidae). However, Cry proteins have been reported to have effects on non-target arthropods. We therefore investigated whether the non-target pest Tetranychus urticae (Acari: Tetranychidae) was negatively affected by GE maize expressing the insecticidal Cry3Bb1 protein. Five treatments were used in the laboratory tests to determine the life history parameters of T. urticae on leaves of field-grown maize varieties: (1) GE maize MON 88017, (2) isogenic maize, (3) isogenic maize protected with the soil applied insecticide chlorpyrifos (Dursban 10G), and two unrelated varieties (4) Kipous and (5) PR38N86. Newly emerged T. urticae larvae were individually released on the upper surface of leaf discs placed on water saturated cotton wool. Immatures and adults survival, duration of developmental stages and female fecundity were recorded daily until T. urticae died. Age–stage, two-sex life table method and test for trends, revealed no significant differences in 13 of 18 studied parameters. The unrelated varieties Kipous and PR38N86 on one side and maize with the same genetic background, namely GE maize and isogenic maize with or without insecticide protection, on the other side, showed significant variations in male longevity, larval survival rate, preoviposition period, and fecundity. In addition to the differences between varieties, GE maize and insecticide-protected isogenic maize showed a substantial difference in age-specific fecundity, but not in the mean number of eggs laid by females.The obtained results do not indicate that consumption of Cry3Bb1 has negative effect on T. urticae and suggest that GE maize does not pose a risk with respect to the non-target mite pest T. urticae. The results may have implications for the approval and renewal of import and cultivation for GE crop in the European Union.