Molecular ecology of some Cecidophyopsis mites (Acari: Eriophyidae) on Ribes species and evidence for their natural cross colonisation of blackcurrant (R. nigrum)

Ribosomal DNA from Cecidophyopsis mites from different Ribes species was amplified using the polymerase chain reaction and the products digested using restriction enzymes. After separating the DNA fragments on gels, it was possible to identify specimens of mites obtained from field samples by comparing the profiles of their DNA banding patterns with those of known Cecidophyopsis species. Using this analysis, a non-gall forming mite found infesting blackcurrant buds in New Zealand was identified as the gooseberry mite (C. grossulariae). On wild red currant (Ribes spicatum) from Finland showing two sizes of galled buds, the red currant gall mite (C. selachodon) was identified in the larger galls located at the tips of branches and a distinct mite in the smaller galls located on the lower parts of the branches. A mite with a DNA banding profile indistinguishable from this latter mite from R. spicatum was also identified in galled buds of blackcurrant genotypes growing in Finland, including those containing the blackcurrant gall mite (C. n'ftw)-resistance genes P or Ce. The DNA banding profile of this mite resembled most closely that of C. ribis , but was distinct from it. The occurrence of C. grossulariae and this distinct Cecidophyopsis mite on blackcurrant has implications for the genetic control of Cecidophyopsis mites and possibly for the spread of the reversion disease agent in this crop.     

Spatial distribution and abundance of bud galls caused by eriophyoid mites among host trees Carpinus tschonoskii

Abstract:  Differences in spatial distribution and abundance of bud galls caused by eriophyoid mites (Acari: Eriophyoidea) among Carpinus tschonoskii (Betulaceae) were studied. This mite preferentially induces galls on terminal buds. Four factors influencing gall abundance were examined: host tree size, host tree's reproductive status, altitude and study site. As tree size increased, the number of galls increased to an apparent asymptote. This result suggests that tree size-dependent characteristics such as number of terminal buds, temporal pattern of shoot elongation and reproductive status influence gall abundance.     

Studies on the fungicidal control of stem lesions caused by Botrytis cinerea on glasshouse tomatoes

In glasshouse pot experiments, uptake of benomyl, thiophanate-methyl and carbendazim from equivalent soil applications (in the range 0–003– 0–035 %^a-i- ^atarateof ²&4 ml/plant) gave equal levels of control of Botrytis lesions developing from inoculations of freshly exposed leaf scars on tomato stems. Spray applications of benomyl to exposed leaf scars controlled infection at concentrations down to 0025 % a.i. The effect of lower concentrations of the stem spray could be markedly enhanced either by the addition of a mineral oil (2 % Actipron) or by a prior soil application of benomyl at a low rate which on its own had little effect on lesion development. Protectant spray applications of glycophene and vinclozolin gave levels of control quite comparable to that of benomyl at equivalent concentrations. Evidence was obtained that the lesions formed at the artificially-inoculated leaf scars at the top of the stems of young pot-grown tomato plants were larger than those lower down. In spite of this, the level of disease control with soil applications of fungicides containing or generating carbendazim (MBC) was greater at the top than at the bottom, probably because of the normal migration of the fungicides and their accumulation at the extremities of the plant. In an observation trial in a commercial crop of tomatoes, benomyl applied either as five soil drenches at approximately monthly intervals, or as two drenches followed by five sprays at three-weekly intervals, or as five sprays alone gave marked reductions in plant loss and number of Botrytis stem lesions in both cvs Eurocross BB and Cudlow Cross. Those stem lesions which did develop, however, were generally as large as those on untreated control plants. Five sprays of dichlofiuanid gave similar levels of disease control. All the treatments gave apparently higher yields (statistically untested) in Eurocross BB, but less consistent responses were recorded in Cudlow Cross.     

Evaluation of fungicides for the control of Verticillium wilt (V. dahliae) of strawberry

The treatment of soil or plants before planting, in September 1969, significantly reduced Verticillium wilt on strawberry in the following season. One application of benomyl or thiabendazole (both 0–5% a.i.) at 6728 l/ha to soil 24 h before planting, dusting roots with formulated benomyl powder (50% a.i.) at planting, or a combination of both benomyl dust + drench treatments were effective. However, although the double treatment gave the most disease control in 1970, plants from the soil-drench treatments gave the highest yields. Residual effects of the 1969 applications were still evident in 1971 from increased vigour, lack of wilt and high yield, especially with the benomyl treatments.     

Galling and reversion disease incidence in a range of blackcurrant genotypes, differing in resistance to the blackcurrant gall mite (Cecidophyopsis ribis) and blackcurrant reversion disease

An assessment was made of the response of 10 blackcurrant genotypes, differing in resistance to the agent of blackcurrant reversion disease (BRD) and to its gall mite vector, in field trials in Scotland and Finland over 5 yr. At each location, the 10 genotypes were planted in plots containing infector plants with high inoculum levels of the two organisms. In Scotland, the infector plants contained large numbers of gall mites (Cecidophyopsis ribis) and were infected with the European (E) form of BRD; in Finland, infector plants contained a different species of gall mite (C. spicata) and the severe Russian form (R) of BRD. As expected, at both sites, almost all plants of cvs Ben Alder, Ben Lomond, Ben Tirran, Ojebyn and an SCRI selection F4/1/66, which are susceptible to gall mite and BRD, became infested with each of these organisms. However, in Scotland but not in Finland, 58% of cv. Ojebyn plants were affected by BRD. The cv. Foxendown, which contains gene Ce that confers apparent immunity to C. ribis, was free from galls and failed to develop distinctive BRD symptoms at both sites. The cvs Rus and Neosypajuscajaija, which contain gene P which is reported to confer resistance to C. ribis, were infested more slowly by mites than the mite-susceptible genotypes and showed a smaller number of galls per plant. Also, they were infected with BRD more slowly than some mite-susceptible genotypes although by the end of the experiment, most plants were affected by BRD. All plants of cvs Golubka and Ben Gairn, which are resistant to the agent of BRD, remained free from distinct BRD symptoms at both sites despite the fact that plants contained galls. These data indicate the superiority of gene Ce over gene P for resistance to gall mites with the added benefit that the virtual immunity to gall mites provided by gene Ce provides a high level of protection against infection with BRD. The relative merits of these different forms of resistance to gall mites and BRD in blackcurrant are discussed in relation to present control methods for these two organisms and in the light of recent findings of different species of eriophyid mites on Ribes species.     

The effect of six systemic fungicides on halo spot disease of barley caused by Selenophoma donacis

Six systemic fungicides were applied at growth stage 10 in a spring-barley field trial, artificially inoculated with Selenophoma donacis at each of three growth stages. Barley cultivars used were Mazurka and Zephyr. The level of disease was significantly reduced by the application of chemicals, benomyl and thiophanate methyl giving the best control. Yield results did not reflect the control of disease although benomyl and thiophanate methyl applications gave slight increases in 1000 grain weight and mean yield per head. Three of the fungicides caused some phytotoxicity in cv. Zephyr and prevented grain formation.     

Effect of insecticides and fungicides on the interaction between members of the mite families Phytoseiidae and Stigmaeidae on citrus

The study was carried out to evaluate the effect of some insecticides and fungicides on the interaction between predacious mites of the families Phytoseiidae and Stigmaeidae on citrus. Euseius citrifolius Denmark and Muma, Euseius concordis (Chant) (Phytoseiidae), and Agistemus aff. bakeri (Stigmaeidae) were the most abundant species of predacious mites. No significant reduction of the population of stigmaeids was detected following the pesticide treatment. On the contrary, the population of those mites increased after the application of methidathion, petroleum oil, deltamethrin, cupric oxychloride and cuprous oxide, as compared to the population of those mites in the control plots. The chemicals promoting increased stigmaeid populations are some of those that promoted reduction of phytoseiid populations. A significant negative correlation was found between the numbers of phytoseiids and stigmaeids on citrus leaves immediately before treatments, and 33, 50, 83 and 105 days after treatment. A clear negative linear correlation between the number of predacious mites from both families was detected for benomyl, cupric oxychloride, cuprous oxide, thiophanate methyl, and control. Phytoseiid-stigmaeid interaction on citrus orchard is discussed.     

Effects of fungicide residues on the survival, fecundity, and predation of the mites Tetranychus urticae (Acari: Tetranychidae) and Galendromus occidentalis (Acari: Phytoseiidae)

Representative fungicides from three or four families used for management of powdery mildew and other diseases in tree fruits were evaluated for their effects on a common spider mite and predator mite species, respectively. A modified Munger cell technique was effective in measuring the response of phytophagous and predaceous mites to fungicide residues on detached leaves in the laboratory. Demethylation-inhibiting (DMI) (imidazole [triflumazole] and triazole [myclobutanil]) and strobilurin (trifloxystrobin) fungicides were not toxic to female Tetranychus urticae Koch and Galendromus occidentalis (Nesbitt), and no sublethal effects were found on fecundity and predation rate after 3-5-d exposure to residues. Benomyl, a benzimidazole fungicide, increased adult mortality and reduced fecundity for both mite species; however, it did not alter the predation rate of G. occidentalis females on T. urticae eggs and larvae. Female G. occidentalis that survived the lethal effects of benomyl and the comparison acaricide pyridaben were unimpaired in predation. Our results for benomyl substantiate those of earlier studies and provide evidence for nontoxic effects of DMI and strobilurin fungicides on mites. We propose that DMI and strobilurin fungicides are a good fit for integrated mite management programs due to conservation of phytoseiid predatory mites.     

Effect of some fungicides on the yield of grass swards

When benomyl, drazoxolon, thiabendazole or zineb were applied as soil drenches to established grassland drazoxolon reduced the incidence of rhizoplane fungi. Benomyl and thiabendazole significantly increased yield at one harvest but only benomyl had a significant effect on total yield. When benomyl was applied at monthly intervals from March to July significant increases in total yield were obtained with the June applications which also significantly increased yield at the first harvest in the following year. Repeated applications from March to July also had a significant residual effect on total yield. Yield increases were not significantly affected by increasing the benomyl level from 2.5 to 5.0 g/m².     

Gall mite Fragariocoptes setiger (Eriophyoidea) changes leaf developmental program and regulates gene expression in the leaf tissues of Fragaria viridis (Rosaceae)

The interaction of plants with certain types of parasites leads to the formation of galls, organised structures that create the habitat of the parasite, caused by an abnormal proliferation of host plant's cells under the influence of growth regulators, secreted by the parasite, or by the plant itself under the influence of the parasite. Arthropods, mites in particular, are the largest group of gall‐inducing phytoparasites, but the mechanisms of their interaction with plants remain virtually unexplored. The interaction of the gall‐inducing eriophyoid mite Fragariocoptes setiger with Fragaria viridis plants was used as a model gall–mite system where data were obtained on the changes in the histological structure of F. viridis leaf blades under the influence of the mites as well as F. viridis gene expression during gall formation. For histological purposes, gall formation was split into four stages with each corresponding to the age of the gall as well as to specific changes that occur during that period. A dramatic change of adaxial–abaxial polarity of the lamina throughout the four stages was observed. Moreover, qRT‐PCR analysis of F. viridis gene expression in the developing gall revealed changes in the expression levels of certain meristem‐specific genes, as well as the genes that determine adaxial–abaxial polarity and signalling of phytohormones.     

Influence of synchronization between adult emergence and host plant phenology on the population density of Pseudasphondylia neolitseae (Diptera: Cecidomyiidae) inducing leaf galls on Neolitsea sericea (Lauraceae)

Synchronization between the appearance of herbivorous insects and their host-plant phenology is a critical event, especially for short-lived insects such as gall midges. We studied a natural population of Pseudasphondylia neolitseae (Diptera: Cecidomyiidae) that induces leaf galls on Neolitsea sericea (Lauraceae) to evaluate the effect of synchronization on gall density in the subsequent generation. To do so, we combined quantitative data on host resources with time lag between emergence and host-available seasons. The gamma distribution model was applied to the emergence curve of P. neolitseae and the normal distribution model to the daily changes in the number of host buds suitable for oviposition; the latter model was transformed into an available-resource curve based on the mean number of host buds required for a single female to realize her eggs. By superimposing the emergence curve on the available-resource curve and calculating overlapped area, the degree of synchronization was evaluated more accurately than previous studies, which had treated only the time lag. The number of females that synchronized with host buds affected gall density in the next generation.     

刺桐姬小蜂发生习性及其虫瘿形成分析

刺桐姬小蜂Quadrastichus erythrinaeKim是新发现的重要入侵害虫,在广东省深圳地区普遍发生且危害严重,受害植株超过10000株。寄主按受害程度依次为:杂色刺桐Erythrina variegata、金脉刺桐E.variegatevar.orientialis、鸡冠刺桐E.cristagalli和龙牙花E.corallodendron。移栽2年内的刺桐树受害严重。根据虫瘿形状,将其分为球形虫瘿、卷叶形虫瘿、肥厚叶虫瘿、分散虫瘿、粗柄形虫瘿、嫩枝肿大虫瘿、花蕾肿大虫瘿并对其形成过程进行分析。首次报道了刺桐姬小蜂为害鸡冠刺桐花蕾。刺桐姬小蜂在深圳无休眠和滞育现象,常年发生。     

Field experiments on the spread of black currant reversion virus and its gall mite vector (Phytoptus ribis Nal.)

In two experiments the spread of reversion virus from a row of systemi-cally infected black currant bushes heavily infested by the gall mite vector (Phytoptus ribis Nal.) was predominantly in the direction of the winds prevailing during the dispersal period. On each side of the sources there was a curvilinear decrease of galled buds and of virus infection as distance increased. In another experiment a central source of mites and virus was surrounded by concentric hexagons comprising alternate rows of healthy and virus-infected bushes. At leaf-fall, galls were forty times more numerous on virus-infected than on healthy bushes; plants in the sector downwind developed the most galls and those upwind the least. On both healthy and virus-infected bushes in each sector, the incidence of galls decreased with increasing distance from the source. The gradients of infestation were steeper on healthy than on virus-infected bushes, especially in sectors upwind from the source. In some sectors the infestation gradients were distorted because many of the virus-infected bushes were so heavily infested that most of the buds became galled. The spread of virus to initially healthy plants decreased from 100 to 75% near the source, to zero at the periphery. More bushes became infected downwind from the source than upwind. In each experiment more bushes developed galls than later produced symptoms of virus infection, the incidence of which was positively correlated with the number of galls recorded the previous winter.     

Morphological and genetic effects of benomyl on polyploid brewing yeasts: isolation of auxotrophic mutants

An enrichment procedure after ethyl methanesulfonate mutagenesis and exposure to the fungicide benomyl yielded mutants auxotrophic for several amino acids from two polyploid Saccharomyces spp. Benomyl treatment was found to have a marked morphological effect on polyploid Saccharomyces cerevisiae, causing cells to adopt a characteristic doublet cell morphology in which buds are nearly as large as the parent cells. Experiments in which nuclear division was monitored in benomyl-induced doublet cells by Giemsa nuclear staining demonstrated an unusual sequence of cytological events which culminated in the formation of binucleate parental and mononucleate bud components. The frequency of formation of doublet and binucleate parent cells was found to depend on the strain employed and the benomyl concentration administered.     

Increased susceptibility of black-currant bushes to the gall-mite vector (Phytoptusribis Nal.) following infection with reversion virus

Healthy black-currant bushes (var. Wellington XXX) and others infected systemically with a virulent strain of reversion virus were exposed equally to infestation by the gall-mite vector (Phytoptus ribis Nal.). Shoots with malformed leaves caused by mites feeding at the stem apices were virtually restricted to the virus-infected bushes. Buds infested with mites became rounded galls, which were far fewer and more localized on shoots of healthy bushes than on infected ones. Similar results were obtained in further experiments with Wellington XXX and seven other varieties. Bushes infected systemically with an avirulent strain of reversion virus developed more galls than healthy bushes, but fewer galls than bushes infected with a virulent strain. The young buds of virus-infected bushes were 170 times more susceptible to dispersing mites than those of healthy bushes. The axillary buds of healthy bushes resisted infestation and the apical meristems were virtually inaccessible to mites, whereas the axillary and apical buds of virus-infected bushes were invaded readily. An experiment with bushes var. Cotswold Cross that were either healthy or partially or completely infected with reversion virus was retained for two years. Each year there was a relationship between symptom expression and mite infestation; only shoots with chronic virus symptoms developed mite-affected leaves and numerous galls. Virus infection increased the vulnerability and accessibility of the apical and axillary buds by decreasing the density of hairs on the stems and leaves. Infected bushes also presented a greater catchment area to dispersing mites and more shoots and buds were available for colonization than on healthy bushes. The interactions between virus, host and vector are discussed, together with their implications in nature, in experimental design and in disease control.     

Morphological and genetic effects of benomyl on polyploid brewing yeasts: isolation of auxotrophic mutants.

An enrichment procedure after ethyl methanesulfonate mutagenesis and exposure to the fungicide benomyl yielded mutants auxotrophic for several amino acids from two polyploid Saccharomyces spp. Benomyl treatment was found to have a marked morphological effect on polyploid Saccharomyces cerevisiae, causing cells to adopt a characteristic doublet cell morphology in which buds are nearly as large as the parent cells. Experiments in which nuclear division was monitored in benomyl-induced doublet cells by Giemsa nuclear staining demonstrated an unusual sequence of cytological events which culminated in the formation of binucleate parental and mononucleate bud components. The frequency of formation of doublet and binucleate parent cells was found to depend on the strain employed and the benomyl concentration administered.     

Seasonal prevalence and susceptibility to agrochemicals of Tyrophagus similis (Acari: Acaridae) in spinach buds and agricultural soil under greenhouse conditions

Seasonal prevalence of Tyrophagus similis was investigated from 1997 to 1998 in two spinach greenhouses in central Japan. Susceptibility of T. similis to agrochemicals was also tested in the laboratory. Tyrophagus similis density in the soil was low during the high temperature period from May to August. The density rapidly increased in late autumn and remained at a high level during the cool season from December to February. The number further increased in April and then rapidly decreased in May. The high temperatures in the greenhouses from spring to early autumn are considered the main causes of population decrease. Mites on spinach buds increased the number after those on and in the soil increased. Mites attacked spinach buds mostly in late autumn and early spring. Dichlorvos did not reduce the number of mites in either greenhouse even though it was highly toxic under laboratory condition. This discrepancy suggests that the mites in both the soil and spinach buds had little direct contact with the chemicals. These data suggest that once crop damage by mites is detected, it is usually too late to use chemicals, and that mites that live in the buds are protected from agrochemicals.     

Use of acephate, benomyl and alginate encapsulation for eliminating culture mites and fungal contamination from in vitro cultures of hardy hibiscus (Hibiscus moscheutos L.)

Summary Shoot cultures of three Hibiscus moscheutos (L.) cultivars were infested with micro-arthropods (mites). Nodal segments (1 cm long) were excised from these cultures and encapsulated in a sodium alginate gelled Driver and Kuniyuki Walnut DKW medium containing 10, 50, or 100 mg l⁻¹ acephate (insecticide) or 10 mg l⁻¹ acephate plus 0, 50, or 100 mg l⁻¹ benomyl (fungicide), then placed in refrigerated (5°C) darkness for 4 wk. Acephate was tested alone if visible fungus was not touching the shoot masses and benomyl was tested if fungus was in contact with the proliferating shoots. Cold-stored encapsulated nodes were then placed on DKW medium with 0.1 μM thidiazuron for 6 wk for subsequent shoot development. The presence of acephate in the encapsulation medium completely eradicated or killed the mites, with 38–69% of cultures fungus-free; 12% of the fungal-contaminated nodes encapsulated with 100 mg l⁻¹ benomyl were fungus-free.     

Effect of different densities of the twospotted spider mite Tetranychus urticae on CO2 assimilation, transpiration, and stomatal behaviour in rose leaves

The effect of population density of Tetranychus urticae Koch on CO2 assimilation, transpiration and stomatal behaviour in rose leaves and on the diameter and length of stems and flower buds was investigated under greenhouse conditions. The investigation was performed in order to gain more insight into integrated control systems in rose crops grown under greenhouse conditions. Physiological processes, such as photosynthesis and transpiration, as well as stomatal behaviour and chlorophyll content, were studied as they form part of the plant's nutrition mechanism and therefore affect the quantity and quality of the flowers. Information related to the effect of spider mite population density on bloom quality, diameter and length of stems and flower buds was also collected. The data indicate that increased mite density coincides with a decrease in the net photosynthetic rate, transpiration and chlorophyll content. Higher mite densities on leaves cause stomata to remain open for longer periods, which allows a greater loss of water. Spider mite densities of 10 and 50 mites per leaf cause a reduction in flower stem length of 17 and 26%, respectively, as compared to plants with no mites present.     

Seasonal prevalence and susceptibility to agrochemicals of Tyrophagus similis (Acari: Acaridae) in spinach buds and agricultural soil under greenhouse conditions

Seasonal prevalence of Tyrophagus similis was investigated from 1997 to 1998 in two spinach greenhouses in central Japan. Susceptibility of T. similis to agrochemicals was also tested in the laboratory. Tyrophagus similis density in the soil was low during the high temperature period from May to August. The density rapidly increased in late autumn and remained at a high level during the cool season from December to February. The number further increased in April and then rapidly decreased in May. The high temperatures in the greenhouses from spring to early autumn are considered the main causes of population decrease. Mites on spinach buds increased the number after those on and in the soil increased. Mites attacked spinach buds mostly in late autumn and early spring. Dichlorvos did not reduce the number of mites in either greenhouse even though it was highly toxic under laboratory condition. This discrepancy suggests that the mites in both the soil and spinach buds had little direct contact with the chemicals. These data suggest that once crop damage by mites is detected, it is usually too late to use chemicals, and that mites that live in the buds are protected from agrochemicals. This revised version was published online in July 2006 with corrections to the Cover Date.