Mite Resistance Research Articles

Organophosphate resistance in spider mites (Acari: Tetranychidae) from cotton in Australia

Tetranychus urticae Koch was resistant to all organophosphates (OPs) tested. The demeton-S-methyl resistance was extremely high (maximum resistance factor (RF) 650 X), as was the dimethoate resistance (maximum RF 750x). The parathion resistance was high (maximum RF 78X), while the profenofos resistance in T. urticae remained stable from 1976 until 1988 (approximately 15X) and that of monocrotophos from 1976 until 1989 (approximately 40X) after which the resistance rose. The resistance in T. urticae peaked in the 1995 season at levels of >100X for profenofos and >400X for monocrotophos, rendering both chemicals ineffective. Tetranychus ludeni Zacher was also resistant to all the OP chemicals tested, but at lower levels than for T. urticae. The LC 50 values indicated that the demeton-S-methyl and monocrotophos resistance in T. ludeni was an order of magnitude less than for T. urticae. The maximum profenofos resistance levels against T. ludeni (6.5 X ) were approximately one-quarter those of the maximum profenofos resistance levels against T. urticae (30X), The parathion LC 50 values and dimethoate RFs indicate T. ludeni to be ultimately only half as resistant as T. urticae. We consider that the relative lack of tolerance to OPs exhibited by T. ludeni may have contributed to it apparent disappearance from Australian cotton. Tetranychus urticae was the dominant mite pest in Australian cotton during 1976-1995. Tetranuchus ludeni reached damaging levels in the late 1970s but virtually disappeared from cotton during the 1980s.

Variation of 2-Tridecanone level in tomato plant leaflets and resistance to two mite species (Tetranychus sp.)

The wild tomato accession Lycopersicon hirsutum f. glabratum ‘PI 134417’ is a promising source of resistance to arthropods in tomato. It is self compatible and intercrosses easily with the cultivated species Lycopersicon esculentum. It is resistant to several arthropods, including spider mites, and these resistances have been related to the presence of high contents of 2-tridecanone (2-TD) and other methyl ketones in the leaves. The objective of this study was to evaluate the contribution of 2-TD concentration in the leaflets of Lycopersicon for resistance to the spider mites Tetranychus urticae (Koch, 1836) and T. ludeni Zacher, 1913. Plants of two segregating generations (F2) were evaluated through the thumbtack bioassay (Weston & Snyder, 1990) in two different assays. Both experiments included as checks L. esculentum ‘TSWV-547’ (mite susceptible), L. hirsutum f. glabratum ‘PI 134417’ (resistant) and the interspecific hybrid F1 (TSWV-547 × PI 134417). In the first experiment, 10 genotypes selected from F2 (TSWV-547 × PI 134417), with contrasting 2-TD concentrations in the leaflets, were tested for resistance to T. urticae. In a second experiment, seven genotypes of the F2 (TSWV-547 × BPX-318p1#230), also with contrasting 2-TD concentrations, were used to evaluate the resistance to T. ludeni. BPX-318p1#230 is a single plant selected from the segregating population F2 (TSWV-547 × PI 134417) for its high 2-TD content. In both experiments, high negative correlations (r = − 0.88; − 0.91 and − 0.93 in the first experiment, and r = − 0.78, − 0.99 and − 0.96 in the second experiment) were found between the 2-TD content and average distance travelled by the spider mites after 60, 90 and 120 minutes, respectively. The level of resistance (repellency) to spider mites T. urticae and T. ludeni in the genus Lycopersicon appears to be mediated by the 2-TD levels present in the tomato leaflets. The similar results of both experiments showed that selection for high 2-TD content in leaflets can lead to genetic improvement in the direction of increased levels of spider mite resistance in tomato.

Comparison of Banks Grass Mite and Twospotted Spider Mite (Acari: Tetranychidae): Responses to Insecticides Alone and in Synergistic Combinations

This research was designed to evaluate responses by Banks grass mite, Oligonychus pratensis (Banks), and twospotted spider mite, TetranychuS urticae Koch, to insecticides alone and in different combinations using 24-h vial bioassays. The twospotted spider mite was more tolerant to many insecticides than the Banks grass mite. Amitraz and S, S, S-tributyl phosphorotrithioate (DEF) synergized 2 organophosphorous insecticides, diazinon and dimethoate, and the pyrethroid bifenthrin against the Banks grass mite. Piperonyl but oxide (PB) antagonized the miticidal activity of esfenvalerate against the Banks grass mite. In contrast to twospotted spider mites, amitraz did not synergize the organophosphorous insecticides, and piperonyl butoxide was a good synergist of the pyrethroid esfenvalerate (98.3-fold increase). DEF synergized bifenthrin and dimethoate against the twospotted spider mite. Mixtures of organophosphorous + pyrethroid mixtures were generally better for twospotted spider mites than Banks grass mites. Insecticide toxicity of the organophosphorous + pyrethroid mixtures was increased from 2.3 to 18.2 times. The synergistic and antagonistic activity of the insecticide + synergist mixtures and organophosphorous + pyrethroid mixtures resulted in twos potted spider mites being less tolerant to several mixtures than were the Banks grass mites. A 3-chemical mixture of dimethoate and bifenthrin with amitraz or piperonyl butoxide caused 52.7- and 94.7-fold increases in toxicity against the twospotted spider mite. The synergistic activity by the chemical mixtures suggest that metabolic degradation and target site insensitivity may be involved in twospotted spider mite resistance. Further studies are needed to improve our understanding of the specific mechanisms in each spider mite species for each organophosphorous and pyrethroid insecticide. The proper insecticide mixture may be an effective tool for managing Banks grass mite and twospotted spider mite infestations.

Inheritance of Biochemical and Morphological Characters Associated with Two-spotted Spider Mite Resistance in Pelargonium ×hortorum

Diploid zonal geraniums (Pelargonium ×hortorum) are able to resist attack by small arthropod pests such as the two-spotted spider mite (Tetranychus urticae Koch) when exudate produced by tall glandular trichomes contains a high percentage of ω5-unsaturated anacardic acids. Trichomes of susceptible plants exude primarily saturated anacardic acids. Inbred mite-resistant and -susceptible geraniums were reciprocally crossed and the F1, F2, and backcross generations were examined for anacardic acid composition and trichome density. Selected F2 plants were bioassayed for resistance to two-spotted spider mites. High concentrations of ω5-unsaturated anacardic acids in resistant plants are conditioned by a single dominant allele. We propose that inheritance of tall glandular trichome density can be controlled by a small number of loci (possibly as few as one) exhibiting codominance. F2, with low densities of tall glandular trichomes and producing ω5-unsaturated anacardic acids, displayed effective resistance to two-spotted spider mites as measured by mite mortality and fecundity. A genetic model for the biosynthesis of anacardic acids is proposed.

Ectoparasitism in Mothers Causes Higher Positional Fluctuating Asymmetry in Their Sons: Implications for Sexual Selection

Random deviations from perfect bilateral symmetry, fluctuating asymmetry, arise from developmental instability. I tested experimentally whether parasitism in female Drosophila nigrospiracula increases fluctuating asymmetry in male offspring. I also developed a novel measure for estimating developmental instability in a meristic trait called positional fluctuating asymmetry, which is based on the difference in the position of thoracic bristles between the right and left sternopleuron. I expected this measure to be a more sensitive indicator of developmental instability than the traditional numerical fluctuating asymmetry, because the latter is based on the difference in the actual presence or absence of bristles. Female flies burdened with hematophagous mites, Macrocheles subbadius (Macrochelidae), produced sons with significantly higher positional fluctuating asymmetry than did females carrying no mites. This effect, which may have resulted from impaired provisioning of oocytes by infested females, was dose dependent and magnified in the progeny of younger (18-20 d) versus older (30-32 d) females. This apparent magnification resulted from a slight but not significant increase in asymmetry of offspring of the older and unparasitized females. In contrast, the same mite loads had no effect on offspring numerical fluctuating asymmetry. If low-positional fluctuating asymmetry males enjoy a mating advantage, then with appropriate genetic variability, sexual selection could drive the evolution of host resistance in host populations. However, variability in neither kind of asymmetry influenced male mating success in nature. Thus, although male positional fluctuating asymmetry is causally associated with parasitism via maternal effects, asymmetry-based sexual selection is unlikely to influence the evolution of mite resistance in D. nigrospiracula. The value of the sensitivity afforded by positional fluctuating asymmetry is discussed in the context of sexual selection and conservation biology.

Clofentezine and fenbutatin oxide resistance in the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) from deciduous fruit tree orchards in Western Australia

The resistance status of Tetranychus urticae Koch to the miticides clofentezine and fenbutatin oxide was investigated in deciduous fruit tree orchards in Western Australia. Mites were collected from 30 orchards across three fruit growing regions and subjected to discriminating–dose assays. There was a significant relationship between clofentezine (=;0.64) and fenbutatin oxide (V=;0.44) use and the proportion of resistant mites in each sample. Improved clofentezine models were obtained when the Perth Hills region (V=;0.90) was modelled separately from Donnybrook and Manjimup (V=;0.80). Clofentezine could be expected to fail in the latter regions after four sprays and in the former region after only one spray. The relatively low pest status of T. urticae in Western Australia did not delay the clofentezine resistance. For any given number of spray applications the response of T. urticae to fenbutatin oxide was more variable than it was to clofentezine.

Development of a mite bioassay to evaluate plant resistance and its use in determining regeneration of spider mite resistance

AbstractThe zonal geranium (Pelargonium xhortorum) possesses tall glandular trichomes that secrete anacardic acids, a viscous, sticky exudate which has been suggested as the primary mechanism in two‐spotted spider mite (Tetranychus urticae Koch) resistance. A new bioassay was developed using small Plexiglas® cylinders as chambers for evaluating the resistance of geranium leaves to the two‐spotted spider mite. This bioassay was easy to prepare, required only 24 hours to conduct, exhibited no problems with desiccation, condensation, or mite accountability, and yielded reproducible results. This bioassay was then used to study the regeneration of resistance of attached geranium leaves after they were made mite‐susceptible by removing the excreted anacardic acids with water. Washed leaves regained full resistance after 14 days.

Molecular characterization of Haynaldia villosa chromatin in wheat lines carrying resistance to wheat curl mite colonization

Wheat-Haynaldia villosa (L.) Schur, hybrid lines were tested as potential sources of resistance to colonization by the wheat curl mite, the vector of wheat streak mosaic virus. Two lines, Add 6V-1 and Sub 6V-1, were found to be mite-resistant. Fluorescence in situ hybridization using total genomic DNA, from H. villosa in the presence of unlabelled wheat DNA, confirmed that Add 6V-1 is a disomic wheat-H. villosa chromosome addition line. Sub 6V-1 turned out to be a homoeologous wheat-H. villosa chromosome translocation line rather than a substitution. The translocation in Sub 6V-1 occurred between a wheat chromosome and a chromosome from H. villosa through Robertsonian fusion of misdivided centromeres. Only the short arm of the group 6 chromosome of H. villosa was involved in the genetic control of mite resistance, a conclusion based on the genomic in situ hybridization signal and specific DNA fragments obtained by polymerase chain reaction.

First data on resistance mechanisms of Varroa jacobsoni (OUD.) against tau-fluvalinate

In 1991, the first losses of efficacy of tau-fluvalinate against the honeybee ectoparasite Varroa jacobsoni Oud. were recorded in Sicily. Since then, diminished efficacy with available pyrethroid treatments has been encountered in many regions of Italy. The aim of this study was to investigate the type of resistance in V. jacobsoni to the pyrethroid tau-fluvalinate by focusing on metabolic resistance mechanisms (detoxication). After developing a suitable application method, two synergists were used: piperonyl butoxide (PBO), as an inhibitor of the microsomal monooxygenases of the cytochrome P450 complex and S,S,S-tributylphosphorotrithioate (DEF), which blocks esterases. A significant decrease in the LC50 values of the susceptible and of the resistant mite strains after the application of PBO was observed. A slight decrease of the LC50 values was also observed after the application of DEF. However, this decrease was not significant. These results indicate that the resistance of Varroa mites to tau-fluvalinate can partly be explained by an increased detoxication due to the monooxygenases in the P450 system, which is blocked by PBO. Esterases seems to play a negligible role. Whether glutathione-S-transferases are involved, is still unknown, but other mechanisms, such as the modification of the binding sites and/or reduced uptake might be involved as well.

Comparative resistance in Buckfast and Canadian stocks of honey bees (Apis mellifera L.) to infestation by honey bee tracheal mites (Acarapis woodi (Rennie))

The results of bioassay and colony evaluation demonstrated that British and Texas Buckfast honey bee stocks had one-third to one-half the mean prevalence and abundance of tracheal mites as Canadian standard stock, indicating that Buckfast stocks are less susceptible to tracheal mites than Canadian standard stock. Hybrid Canadian and Buckfast stocks exhibited resistance characteristics similar to only one of their parental stocks, suggesting the colony has an unknown effect on the expression of a bee's resistance to mites. A high correlation (rs=0.66) between abundance values from the bioassay and colony evaluations indicates that the bioassay can be used to screen bees for mite resistance.

Resistance to Wheat Curl Mite (Acari: Eriophyidae) in Greenbug-Resistant ‘Gaucho’ Triticale and ‘Gaucho’ X Wheat Crosses

Greenbug-resistant “Insave F.A.” rye, “Gaucho” triticale, and crosses of Gaucho x wheat. Sel. 74G80-2 and Sel. 74G559-6, were compared with wheat cultivars for their reaction to the wheat curl mite, Eriophyes tulipae Keifer, the vector of wheat streak mosaic virus. It was previously observed that rye generally is more resistant to the mite than wheat. In our study, Gaucho, which is the product of an Insave F.A. rye X ‘Chinese Spring’ wheat cross, and wheat lines derived from Gaucho X wheat crosses, showed a high degree of resistance to the mite, whereas the susceptible entries exhibited severe mite damage symptoms including leaf curling and trapping and large numbers of mites. The wheat streak mosaic virus was transmitted to all test entries by heavy initial infestations of viruliferous mites. Light infestations of 5 mites per plant did not result in disease symptoms, except in mite-susceptible entries. The results also indicate that the source of wheat curl mite resistance in ‘TAM 107’ wheat, widely planted in wheat streak virus-prone areas of the Great Plains, traces back to Gaucho triticale.

Gualamycin, a novel acaricide produced by Streptomyces sp. NK11687. I. Taxonomy, production, isolation, and preliminary characterization.

A novel acaricide, gualamycin, was isolated from the culture broth of Streptomyces sp. NK11687. It was purified from the filtrate by column chromatographies. Gualamycin showed 100% acaricidal activity at 250 micrograms/ml against sensitive and resistant mites to Dicofol.

Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC50 value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC50 values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.

Detection and Characterization of the Interpopulation Variation of Citrus Rust Mite (Acari: Eriophyidae) Resistance to Dicofol in Florida Citrus

Methods to rear and bioassay the citrus rust mite, Phyllocoptruta oleivora (Ashmead), were developed to detect and characterize resistance to dicofol. Sustained rearing of P. oleivora was achieved on ‘Sunburst’ mandarin seedlings [Citrus reticulate Blanco × (C. paradise Macf. × C. reticulata)] held in Plexiglas cages in the greenhouse. Residual bioassays with dipped or sprayed citrus seedling leaves were used to evaluate the susceptibility to dicofol of P. oleivora populations from groves with known history of its use. Mite populations from groves with no history of dicofol use had significantly higher susceptibility to dicofol than groves in which dicofol was used regularly. Methods using dipped or sprayed leaves gave similar results. With the leaf-dip method, the LCM50 of a susceptible field population (2.81 µmg dicofol/ml distilled water [ppm (AI)]; 95% CL 2.32-3.26) was 8.8 times lower than for a field population selected with dicofol in the laboratory (24.7 ppm [AI]; 95% CL 20.8-28.2). Based on this difference, we established a diagnostic concentration of 10 ppm (AI) for detecting dicofol-resistant mites, with a leaf-dip bioassay. Results of a survey of 19 commercial Florida citrus groves, in which we used diagnostic concentration bioassays to determine susceptibility of P. oleivora to dicofol, revealed significant differences between populations, thus confirming resistance to dicofol.

Application of Fatty Acids To Elicit Lipoxygenase-Mediated Host- Plant Resistance to Twospotted Spider Mites (Acari: Tetranychidae) in Phaseolus vulgaris L.

It has been hypothesized that fatty acid oxidation products from the lipoxygenase (LOX) pathway can play an important role in plant defense against herbivorous arthropods. Studies were conducted to investigate whether LOX substrate treatment is correlated with defense against spider mites. Excised leaf tissue from Phaseolus vulgaris L. seedlings was treated with several fatty acid substrates of the LOX enzyme complex. Spider mites confined to treated tissue exhibited reduced fecundity relative to untreated controls. The same fatty acid solutions were applied to intact seedlings and allowed to grow for 7 d. Mites were then individually caged on newly emerged leaves and their fecundity monitored for 20 d. Mites on seedlings treated with those fatty acids that are LOX substrates exhibited fecundity reductions similar to that reported previously in bioassay studies where mite resistance was induced by wounding or prior mite feeding. These results suggest that a proposed biochemical basis for this systemically acquired resistance mechanism is probably substrate limited.

Cytological and molecular characterization of a chromosome interchange and addition lines in Cadet involving chromosome 5B of wheat and 6Ag of Lophopyrum ponticum

Efforts to transfer wheat curl mite (Eriophyes tulipae Keifer) resistance from Lophopyrum ponticum 10X (Podb.) Love to bread wheat (Triticum aestivum L.) have resulted in the production of a number of cytogenetic stocks, including an addition line of 6Ag, a "ditelo" addition line, and a wheat-Lophopyrum translocation line. Characterization of these lines with C-banding, in situ hybridization with a Lophopyrum species-specific repetitive DNA probe (pLeUCD2), and Southern blotting with pLeUCD2 and a 5S ribosomal DNA probe (pScT7) confirmed that the distal portion of the short arm of 6Ag was translocated onto the distal portion of 5BS (5BL. 5BS-6AgS). It was also determined that the "ditelo" addition was an acrocentric chromosome of 6AgS.

In Vitro Screening of 76 Strawberry Cultivars for Twospotted Spider Mite Resistance

Leaf disk bioassays based on oviposition and damage accrued during 72 hours were used to screen 76 strawberry (Fragaria spp.) cultivars for resistance to the twospotted spider mite (Tetranychus urticae Koch). Oviposition rates (eggs/female per day) and damage scores were both highly variable, allowing cultivars to be classified, according to a combination of these two variables, into six categories of susceptibility or resistance: highly susceptible- `Canoga', `Ozark Beauty', `Scott', and `Tangi'; resistant—'Aiko', `Annapolis', `Apollo', `Bounty', `Cardinal', `Douglas', `Dover', `Fairfax', `Fern', `Floridabelle', `Glooscap', `Governor Simcoe', `Hecker', `Kent', `Pajaro', `Parker', `Rainier', `Redcoat', and `Vesper'; and highly resistant—`Profumata di Tortona' (F. moschata Duch.). Bioassay based on oviposition rates and damage scores was considered to be an efficient method to eliminate susceptible accessions from a breeding program, but authentication of putative resistance may require further testing in vivo.

Planting Date and Plant Density Effects on Condensed Tannin Concentration of Cotton

Condensed tannins are feeding deterrents to cotton bollworm [Helicoverpa zea (Boddie); syn. Heliothis zea], tobacco budworm [Helicoverpa virescens (F.); syn. Heliothis virescens], and spider mite (Tetranychus urticae Koch) in cotton (Gossypium hirsutum L.). This study was conducted to determine the effects of planting date and plant density on the condensed tannin concentrations of six plant parts of cotton sampled at two growth stages at College Station, TX, in 1988 and 1989. Cotton was sown every 2 wk to provide three planting dates beginning on 25 April in both years. Genotypes evaluated were ‘Tamcot CD3H’, ‘Arkot 518’, and four high‐tannin lines (TAM 86III24, TAM 86E3, TAM 86E8, and 86CC2) selected for spider mite resistance. The topmost unfolded leaf, a fourth mainstem leaf from the terminal, a 6‐d‐old bract, a 10‐d‐old sepal, and a bract and a sepal from a white bloom were sampled at first bloom and at 2 wk post first bloom from plants spaced 8 and 30 cm within rows spaced 1.02 m apart. Younger tissue consistently had a higher condensed tannin concentration than mature tissue. Condensed tannin concentrations were highest in TAM 86III24 and lowest in the two commercial cultivars, Arkot 518 and Tamcot CD3H. TAM 86E8, TAM 86E3, and 86CC2 were intermediate in tannins. Breeding cotton for high tannin concentration would require consideration of the tissue sampled because of the interaction of genotype with this factor.

The Prospects of Tissue Culture and Genetic Engineering for Strawberry Improvement

Abstract Strawberry shoot meristem cultures have been used for producing virus-free strawberry plants. Plantlet regneration from leaf mesophyll protoplasts, and Agrobacterium tumefaciens mediated genetic transformation, mark the beginning of strawberry improvement with biotechnologies. The use of biotechnological tools has a greater potential in producing strawberry plants with traits such as early maturation, frost and disease resistance, mite and nematode resistance, high yield, better quality, suitability for mechanical harvesting, shipping ability, ellgaic acid content, aroma compounds and cost-effective micropropagation. Gene identification and mapping with RFLPs or RAPDs would be desirable. Transgenic strawberries should be tested for their quality before releasing to the consumers.

Enhanced activation is the mechanism of negative cross-resistance to Chlorpyrifos in the Dicofol-IR strain of Tetranychus urticae (Acari: Tetranychidae).

The mechanism responsible for negative cross-resistance to chlorpyrifos was examined in isogenic dicofol susceptible (Orchard-12) and resistant (Dicofol-IR) two-spotted spider mites, Tetranychus urticae Koch. The acetylcholinesterase of both strains was equally sensitive to inhibition by chlorpyrifos oxon. However, the Dicofol-IR strain showed increased oxidative activation of chlorpyrifos to chlorpyrifos oxon relative to the Orchard-12 strain, suggesting this mechanism is responsible for the observed negative cross-resistance.