Susceptible Mites Research Articles

A Simple Method for Testing Spider Mite Susceptibility to Acaricides Using Body Fluid Stains in an Envelope

A Simple Method for Testing Spider Mite Susceptibility to Acaricides Using Body Fluid Stains in an Envelope

A microRNA-1 gene, tci-miR-1-3p, is involved in cyflumetofen resistance by targeting a glutathione S-transferase gene, TCGSTM4, in Tetranychus cinnabarinus.

microRNA-1 (miR-1) is a well-studied conservative microRNA (miRNA) involved in immune responses in mammals and insects. However, little is known about its role in pesticide resistance in arthropods. In this study, we found that a microRNA belong to miR-1 family (tci-miR-1-3p) was significantly down-regulated in a cyflumetofen-resistant strain (CYR) of Tetranychus cinnabarinus compared with its homologous susceptible strain (SS), indicating an involvement of miR-1 in cyflumetofen resistance inmites. One glutathione S-transferase (GST) gene (TCGSTM4, a mu class GST gene), a candidate target gene of tci-miR-1-3p, was found to be significantly down-regulated when tci-miR-1-3p was over-expressed. The specific interaction between tci-miR-1-3p and the target sequence in the 3' untranslated region of TCGSTM4 was confirmed. A decrease or increase in tci-miR-1-3p abundance through feeding miRNA inhibitors or mimics significantly increased or decreased TCGSTM4 expressions at the mRNA and protein levels, respectively. In addition, an over-expression of tci-miR-1-3p resulted in a decrease in the tolerance of T. cinnabarinus to cyflumetofen in both SS and CYR strains, and vice versa. After decreasing TCGSTM4 transcription via RNA interference, T. cinnabarinus became more sensitive to cyflumetofen in both resistant and susceptible mites, and the change in mortality was greater in CYR than that in SS. Moreover, the recombinant TCGSTM4 could significantly decompose cyflumetofen, indicating that TCGSTM4 is a functional gene responsible for cyflumetofen resistance in mites.

Ambulatory dispersal of the susceptible and propargite-resistant strains of Tetranychus urticae and its influence on pesticide resistance dynamics

The distribution of resistant individuals is determined by the amount of movement between populations. The differential rate of dispersal of a susceptible and a pesticide-resistant strain could influence the resistance dynamics under field conditions. The dispersal rate and dispersal efficiency of the susceptible and propargite-resistant strains of Tetranychus urticae were measured in separate-release and mixed-release experiments. The diffusion coefficient (D) of both strains did not differ significantly (P>0.344) and an estimate of the asymptotic rate of advance (2√rD) (for one generation) was estimated at 0.1047 and 0.0930cm per degree day for the susceptible and propargite-resistant strains, respectively. The dispersal efficiency of the two strains differed significantly (P<0.005) as more susceptible mites than propargite-resistant mites crossed into specified zones more quickly after 290 and 366 degree days. Significantly (P<0.05) higher number of susceptible adults, immatures and eggs were found in the outer most zone of an arena as compared to that of the propargite-resistant mites. The bioassay of the two strains showed a similar pattern of the spread of the adult females across the specified zones in the mixed-release experiment. The relatively lower dispersive tendency of the propargite-resistant T. urticae and the smaller proportion of adult females exhibiting that behaviour increase the chances of developing resistant ‘hotspots’ in field specially after an acaricide application.

Comparative life table analysis of Tetranychus urticae Koch (Acari: Tetranychidae) on ten rose cultivars

Life history parameters of plant feeders are useful tools to evaluate resistance or susceptibility of host plants including different cultivars. This study compared population growth parameters of Tetranychus urticae Koch on 10 rose cultivars, including Bella Vita, Cool Water, Dolce Vita, Maroussia, Orange Juice, Pink Promise, Roulette, Tea, Valentine, and Persian yellow in laboratory conditions at 24+/-1°C, 65+/-5% relative humidity, and a photoperiod of 16:8 (L:D) h. The results revealed that mite survival rate varied from 66.5% on Bella Vita to 85.9% on Persian yellow. The immature development time was different among the tested rose cultivars and ranged from 9.35 days on Orange Juice to 12.30 days on Bella Vita. The highest fecundity rate was recorded on Pink Promise. Consequently, population growth parameters were also significantly affected. The lowest intrinsic rate of increase (rm) was recorded on Roulette and this parameter was relatively higher on Cool Water, Orange Juice, and Persian yellow. In addition, the highest net reproductive rate (R0) was observed on Pink Promise, which was significantly higher than Roulette, Tea, and Valentine cultivars. The longest mean generation time (T) was calculated on Roulette and the shortest on Cool Water, Tea, and Orange Juice. The lowest performance of the two-spotted mite on Roulette could indicate that this is a suitable cultivar against mite infestation. Differences in mite susceptibility of tested rose cultivars here highlighted have the potential to be used for integrated pest management of T. urticae in ornamental rosa cultivations.

High Gama-Aminobutyric Acid Contents Involved in Abamectin Resistance and Predation, an Interesting Phenomenon in Spider Mites.

Abamectin has been widely used as an insecticide/acaricide for more than 30 years because of its superior bioactivity. Recently, an interesting phenomenon was identified in the carmine spider mite, Tetranychus cinnabarinus, an important pest in agriculture. The gamma aminobutyric acid (GABA) contents in a laboratory abamectin resistant strain of T. cinnabarinus (AbR) were significantly increased. Decreases in activity and mRNA expression of GABA transaminase (GABA-T) were responsible for GABA accumulation in AbR mites. To clarify the mechanism of GABA accumulation mediated abamectin resistance, three artificial approaches were conducted to increase GABA contents in susceptible mites, including feeding of vigabatrin (a specific inhibitor of GABA-T), feeding of exogenous GABA, and inhibition of GABA-T gene expression. The results showed that susceptible mites developed resistance to abamectin when the GABA contents were artificially increased. We also observed that the mites with higher GABA contents moved more slowly, which is consistent with the fact that GABA is an inhibitory neurotransmitter in arthropods. Subsequently, functional response assays revealed that predation rates of predatory mites on GABA accumulated abamectin-resistant mites were much higher than control groups. The tolerance to abamectin, slow crawling speed, and vulnerability to predators were all resulted from GABA accumulation. This relationship between GABA and predation was also confirmed in a field-collected population. Our finding indicates that predatory mites might be used as a tool for biological control to circumvent the development of abamectin resistance in mites.

Inheritance of acaricide resistance in inbred strains of the two-spotted spider mite

Disruptive selection has been used to obtain the inbred two-spotted spider mite strains resistant to four insectoacaricides—dimethoate, bifenthrin, abamectin, and bromopropylate. The resistance ratios (RRs) for the mites in families of the selected strains are 1000-, 2600-, 2000-, and 2000-fold, respectively. The distribution according to mortality rate of the F1 families in the crosses of resistant and susceptible mite strains and Fa backcrosses has shown a monogenic dominant inheritance of the dimethoate resistance, digenic dominant inheritance of the abamectin resistance, and digenic incompletely recessive inheritance of the bifenthrin and bromopropylate resistances. The data on the cross-resistance to acaricides of different chemical classes suggest that the genomes of the selected mite strains carry mutations conferring resistance to the corresponding toxicants.

Presence of &amp;lt;i&amp;gt;Mycoplasma&amp;lt;/i&amp;gt; Spp. in Patients with Asthma or Allergic Rhinitis

Objective: To compare the presence of Mycoplasma spp. in pharyngeal swabs of patients with asthma, allergic rhinitis and controls, also to compare the reactivity to allergens in the three groups. Material and Methods: Throat swabs of 120 patients with asthma, 211 allergic rhinitis patients and 171 healthy persons were cultured in E media. Positive cultures were identified by PCR. Susceptibility of patients positive for isolation of Mycoplasma spp. to indoor, forest and undergrowth allergens were determined. Results: Mycoplasma spp. was isolated in 26.6% of samples from asthmatic patients, 36% in patients with allergic rhinitis and 2.9% in the group of healthy persons. Positive patients for Mycoplasma with asthma and allergic rhinitis showed susceptibility tomite, grass and thunder mainly. Conclusion: There is a higher incidence of Mycoplasma spp. in asthmatic and allergic rhinitis patients than healthy persons. Only patients with asthma or allergic rhinitis showed reactivity to environmental allergens.

Chlorfenapyr resistance in the spider mite Tetranychus urticae: stability, cross-resistance and monitoring of resistance

The two-spotted spider mite, Tetranychus urticae Koch, is a key pest of many agricultural crops. Studies of stability of resistance, cross-resistance relationships and monitoring of chlorfenapyr resistance were carried out with T. urticae to provide basic information necessary to define effective acaricide resistance management strategies for this pest. Chlorfenapyr resistance was shown to be stable in the absence of selection pressure under laboratory conditions. The activities of seven different acaricides against chlorfenapyr-resistant and -susceptible strains of T. urticae were evaluated. The results indicated possible positive cross-resistance between chlorfenapyr and the acaricides abamectin, propargite and etoxazole. No cross-resistance was detected for the acaricides milbemectin, fenpyroximate and diafenthiuron. A possible negatively correlated cross-resistance was observed between chlorfenapyr and spiromesifen. The evaluation of 21 T. urticae populations from several crops in the States of Sao Paulo, Mato Grosso, Goias, and Bahia, in Brazil, indicated that the susceptibility of mites to chlorfenapyr was variable, with percentages of resistant mites ranging from 0.0 to 86.5%. The highest resistance frequencies were observed in ornamental plants in the State of Sao Paulo. Some populations from cotton and papaya also presented high frequencies of chlorfenapyr resistance. This is the first report on chlorfenapyr resistance in T. urticae on cotton and papaya in Brazil. Strategies for the management of acaricide resistance are discussed.

‘Summer Skies’ Buddleja davidii

Buddleja davidii Franch., commonly called butterfly bush, is a large woody subshrub with long, colorful, fragrant floral panicles, which attract hummingbirds and butterflies. It was originally introduced to the United States from China and is a winter-hardy perennial throughout most of the United States to USDA hardiness zone 5 (–26 to –29 C). It is an important and favored landscape ornamental with over 100 named cultivars (Dirr, 2009; Stuart, 2006). Variegated forms of plants are popular because the foliage provides ornamental color interest when plants are not in flower. Some variegated butterfly bush cultivars have been introduced, including ‘Harlequin’, ‘Notbud’ Masquerade , ‘Santana’, and ‘White Harlequin’, but they have often performed poorly as a result of chimera instability, leaf scorch or leaf ‘‘greening’’ in summer heat, poor vigor, or spider mite susceptibility. A new variegated cultivar of Buddleja davidii named ‘Summer Skies’ was generated through the use of chemical mutagenesis. The leaves of this cultivar have a striking periclinal variegation, which is highly stable. The central portion of the leaves are dark green with a broad and variable edge of bright yellow to white depending on the amount of sunlight the plant receives. ‘Summer Skies’ performed well in trials in comparison with several commonly available cultivars, exhibiting strong vigor and attractive variegation throughout the growing season. ‘Summer Skies’ has been released to provide a cultivar with improved variegation and landscape performance that can extend the ornamental appeal of butterfly bush to the spring and early summer periods before the start of flowering.

Control of Tetranychus urticae Koch by extracts of three essential oils of chamomile, marjoram and Eucalyptus

Objective To evaluate the acaricidal activity of extracts of three essential oils of chamomile, marjoram and Eucalyptus against Tetranychus urticae ( T. urticae) Koch. Methods Extracts of three essential oils of chamomile, marjoram and Eucalyptus with different concentrations (0.5%, 1.0%, 2.0%, 3.0% and 4.0%) were used to control T. urticae Koch. Results The results showed that chamomile ( Chamomilla recutita) represented the most potent efficient acaricidal agent against Tetranychus followed by marjoram ( Marjorana hortensis) and Eucalyptus. The LC 50 values of chamomile, marjoram and Eucalyptus for adults were 0.65, 1.84 and 2.18, respectively and for eggs 1.17, 6.26 and 7.33, respectively. Activities of enzymes including glutathione-S-transferase, esterase (α-esterase and β-esterase) and alkaline phosphatase in susceptible mites were determined and activities of enzymes involved in the resistance of acaricides were proved. Protease enzyme was significantly decreased at LC 50 of both chamomile and marjoram compared with positive control. Gas chromatography-mass spectrometer (GC-MS) proved that the major compositions of Chamomilla recutita are α-bisabolol oxide A (35.251%), and trans-β-farersene (7.758%), while the main components of Marjorana hortensis are terpinene-4-ol (23.860%), p-cymene (23.404%) and sabinene (10.904%). Conclusions It can be concluded that extracts of three essential oils of chamomile, marjoram and Eucalyptus possess acaricidal activity against T. urticae.

Acaricidal activity of different extracts from Syzygium cumini L. Skeels (Pomposia) against Tetranychus urticae Koch

Objective To investigate the acaricidal activity of different extracts from Syzygium cumini ( S. cumini) (Pomposia) againsst Tetranychus urticae Koch ( T. urticae) and the biochemical changes in antioxidants enzymes. Methods Six extracts of S. cumini (Pomposia) at concentrations of 75, 150 and 300μg/mL were used to control T. urticae (Koch). Results The ethanol extract showed the most efficient acaricidal activity agent against T. urticae (98.5%) followed by hexane extract (94.0%), ether and ethyl acetate extract (90.0%). The LC 50 values of the promising extract were 85.0, 101.0, 102.0 and 98.0μg/mL, respectively. The activities of enzymes including ascorbate peroxidase (APX), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in susceptible mites were increased. The activities of all antioxidant enzymes reach the maximum value in mites at LC 50 with ethanol and ethyl acetate extracts, respectively. Conclusions The extract of S. cumini has acaricidal acivity against T. urticae, and the ethanol extract is the most efficient.

Susceptibility of Varroa destructor (Acari: Varroidae) to synthetic acaricides in Uruguay: Varroa mites’ potential to develop acaricide resistance

The purpose of this study was to estimate the acaricide susceptibility of Varroa destructor populations from Uruguay, which had never been exposed to synthetic acaricides. It was also to determine whether acaricide resistance to coumaphos occurred in apiaries in which acaricide rotation had been applied. Bioassays with acaricides against mite populations that had never been exposed to synthetic acaricides were performed, also against mite populations in which control failures with coumaphos had been reported. Additionally, coumaphos' effectiveness in honeybee colonies was experimentally tested. The lethal concentration that kills 50% of the exposed animals (LC(50)) for susceptible mite populations amounted to 0.15 μg/Petri dish for coumaphos and to less than 0.3 μg/Petri dish for the other acaricides. Coumaphos LC(50) was above 40 μg/Petri dish for resistant mites. The effectiveness of coumaphos in honeybee colonies parasitized by V. destructor ranged from 17.6% to 93.9%. LC(50) for mite populations susceptible to the most commonly applied miticides was determined, and the first case of coumaphos resistance recorded in Uruguay was established.

Resistance phenomena to amitraz from populations of the ectoparasitic mite Varroa destructor of Argentina

In Argentina, Varroa destructor resistance to coumaphos has been previously reported. However, the status of mite susceptibility to other hard acaricides is still unknown. At present, high infestation levels of V. destructor are being detected in colonies of Apis mellifera after treatment with amitraz. The aim of the present study was to determine the LC(50) of amitraz in V. destructor from three apiaries with high mite density after treatment with the acaricide. The LC(50) values were 3.9, 3.5, and 3.7μg/Petri dish for mites from three different apiaries. Significant LC(50) differences were detected between resistant and susceptible mites. LC(50) increased 35-39-fold when compared to the corresponding baseline, suggesting the development of resistance. These results are the first report of resistance to amitraz in V. destructor in Argentina and extend the knowledge according to the status of acaricides resistance in the country.

Evaluation of a Sib-mated Population of Buddleja davidii ‘White Bouquet’ × Buddleja indica Hybrids

Abstract A hybridization experiment to sib-cross a population of B. davidii Franch. ‘White Bouquet’ × B. indica Lam. hybrids was initiated in 2004 to generate a larger population of such hybrids to assess landscape potential. Large populations from the sib-mated B. davidii ‘White Bouquet’ × B. indica hybrids can be generated. The population was initially assessed for growth habit, leaf size, floriferousness, seed morphology, and winter hardiness. Susceptibility to spider mite damage was also noted in the population. Although these hybrids have desirable traits such as non-dehiscent fruit and ornamental foliage, further hybridization is needed to address undesirable traits such as sparse growth and flowering along with spider mite susceptibility.

First detection of Varroa destructor resistance to coumaphos in Argentina

In Argentina, studies on Varroa destructor resistance to coumaphos are still unknown. At present, high infestation levels of V. destructor are being detected in colonies of Apis mellifera after treatment with this acaricide. The aim of the present study was to determine the LC50 of coumaphos in V. destructor from four apiaries with high mite density after treatment with coumaphos. The LC50's were 112, 319, 127 and 133 microg/Petri dish for mites from the four apiaries. Significant LC50 differences were detected between resistant and susceptible mites. LC50 increased 197-559-fold when compared to the corresponding baseline, suggesting the development of resistance. These results are the first report of resistance to coumaphos in V. destructor in Argentina.

Detection of fluvalinate resistance in Varroa destructor in Spanish apiaries

SummaryA laboratory assay developed by Milani (1995) was used to assess the susceptibility to the acaricide fluvalinate in 10 populations of Varroa destructor Anderson and Trueman from apiaries in Aragón (northeastern Spain). We assayed mites at the diagnostic concentration (200mg/kg) predicted to kill all susceptible mites. In some populations, LC50 values were obtained. Some mites were resistant to fluvalinate, which is the first reported case of fluvalinate resistance in Varroa destructor in Spain. Thus, it is inadvisable to base mite control strategies on chemical treatment alone. There is urgent need to expand and implement more biorational strategies in the fight against V. destructor.

Inheritance of Resistance to Two-spotted Spider Mite and Glandular Leaf Trichomes in Wild Tomato Lycopersicon pimpinellifolium (Jusl.) Mill.

Genetics of resistance to Tetranychus urticae Koch and of glandular trichomes of Lycopersicon pimpinellifolium accession TO-937 in a cross between susceptible L. esculentum Mill. `Moneymaker' and resistant TO-937 was studied in a greenhouse experiment. Parents, F1, F2, and two BC1 generations, interspersed with susceptible tomato plants to avoid negative interplot interference, were artificially infested. Mite susceptibility was evaluated by a rating based on plant capacity to support mite reproduction. TO-937, BC1 to TO-937, and F1 were resistant, `Moneymaker' susceptible, and the F2 and the BC1 to `Moneymaker' segregated. Resistance was controlled by a single dominant major locus, but modulated by unknown minor loci. TO-937 presented type IV glandular trichomes, their presence governed by two dominant unlinked loci. Type IV trichome density correlated to resistance; however, a causal relationship between type IV trichomes and mite resistance could not be definitively established. The relatively simple inheritance mode will favor successful introgression of resistance into commercial tomatoes from the close relative L. pimpinellifolium.

First report of Varroa destructor resistance to pyrethroids in the UK

Varroa destructor resistance to pyrethroids has been reported in mainland Europe since the early 1990's. V. destructor was first detected in the UK in 1992 and since then there has been widespread use of the only two authorised pyrethroid treatments. A routine national screening programme for resistance to pyrethroids was established in 2000 and in August 2001 resistance was detected in southwest England. The resistance outbreak was limited to 25 apiaries, was associated with product misuse, and the resistance factors to fluvalinate and flumethrin were approximately 10 fold when compared to susceptible mites. There was no cross-resistance with amitraz, coumaphos or cymiazole. This level of resistance is far lower than that detected following widespread colony collapse in Italy and highlights the importance of the correct use of varroacides and of early detection of resistance to enable its control. Varroa destructor / resistance / pyrethroid / monitoring

Decline in the proportion of mites resistant to fluvalinate in a population of Varroa destructor not treated with pyrethroids

The reversion of resistance to pyrethroids in Varroa destructor Anderson & Trueman was studied in Friuli (northern Italy), where resistance was detected in 1995 and pyrethroids had not been used since. Mites were sampled in seven localities each year between 1997 and 2000 and assayed in the laboratory for the resistance to fluvalinate by using paraffin coated capsules. Survival at the diagnostic concentration, expected to kill all susceptible mites (200 mg/kg), decreased in all the localities by about ten times in three years, from 19-66% to 1.3-7.8%. Thus, the disadvantage associated with the resistance to pyrethroids in V. destructor is small, as usual when resistance is due to monooxygenases. Its impact on the selection of resistant mites during annual application of treatments is negligible; appreciable effects of reversion can be expected only over many generations of the mite. Varroa destructor / reversion / resistance / pyrethroids

Effect of acaricide resistance on reproductive ability of the honey bee mite Varroa destructor.

The reproduction of pyrethroid-resistant Varroa destructor mite, a brood parasite of honey bees, was observed in Weslaco, Texas, and the results compared with known susceptible mite populations from other studies. Seven Apis mellifera colonies that had mite populations resistant to the acaricide Apistan were used. Pyrethroid-resistance was confirmed when only 17% rather than 90% of mites confined in dishes containing Apistan died after 12 h of exposure. The average number of eggs laid by resistant mites invading worker and drone cells was 4.4 and 5.4 respectively. This is similar to the number of eggs laid by susceptible mites in worker (4.4-4.8) or drone (4.7-5.5) cells. Also the average number of fertilised V. destructor female mites produced by resistant mites in worker (1.0) and drone (2.1) cells were similar to the number produced by susceptible mites in worker (0.9) and drone (1.9-2.2) cells. In addition, no major differences between the resistant and susceptible mite populations were observed in either worker or drone cells when six different reproductive categories and offspring mortality rates were compared. Therefore, it appears that there is little or no reproductive fitness cost associated with pyrethroid resistance in V. destructor in Texas.