European Red Mite Populations Research Articles

Phylogenetic relationship between Dermanyssus gallinae populations in European countries based on mitochondrial COI gene sequences

Phylogenetic analysis of Dermanyssus gallinae mites originating from UK, France and Italy was performed using partial amplification of the mitochondrial COI gene. Results showed that UK samples reveal the greatest variation and diversity and are linked to one of the French populations highlighting North-South genetic transitions in European red mite populations. Intra-farm variations between mite samples highlighted the diversity between national populations and possibly its origin from the different chemical strategies used in each country.

Effectiveness of azadirachtin (NeemAzal-T/S) in controlling pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi)

Here we present the results of field trials conducted in Serbia to evaluate the effectiveness of a neem-based product, NeemAzal-T/S (containing azadirachtin-A as its active ingredient in the form of an emulsifiable concentrate) against pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi). Efficacy evaluation against C. pyri was carried out in a commercial pear orchard of the Williams pear cultivar, located at Borkovac (Ruma). The insecticides were applied at BBCH 09 pear growth stage, several days before the beginning of hatching of the first generation larvae. The efficacy of azadirachtin was compared to that of mineral oil, abamectin and diflubenzuron. Efficacy evaluation 18 DAT showed total termination of egg laying by C. pyri after treatments with azadirachtin and abamectin, while some new (white) eggs were found after treatment with mineral oil. Diflubenzuron treatment failed to fully stop egg laying, but the number of white eggs was significantly lower than it was in the control. Azadirachtin and abamectin achieved 100% efficacy, while the effectiveness of mineral oil was 97.4%, and that of diflubenzuron a mere 59%. All four insecticides significantly reduced the number of older (yellow) eggs and larvae, the efficacy being 80.5-92.6% (yellow eggs), 69.8-79.3% (larvae I-III instar) and 94.3-100% (larvae IV-V instar). In evaluation 38 DAT, azadirachtin, abamectin and mineral oil achieved 100% efficacy against white and yellow eggs, while diflubenzuron achieved 93% and 86.9% efficacy. All four insecticides were found to demonstrate high efficacy against I-III instar larvae (99.2-100%), but mineral oil treatment alone achieved high efficacy against IV-V instar larvae (92.4%) as well. Efficacy evaluation against P. ulmi was carried out in a commercial orchard of the Red Chief apple cultivar located at Morovic (Sid). Azadirachtin efficacy in controlling a summer population of European red mite was compared to a mineral oil, clofentezine and spirodiclofen. The acaricides were applied when the number of P. ulmi motile forms was below the orientational damage threshold of 3 motile forms per leaf. Azadirachtin reduced significantly the number of motile forms, leaving it well below damage threshold by the end of the trial. Good control efficacy was achieved (77.2-90.4%), the highest level of efficacy being recorded at the end of the trial 38 DAT. In mineral oil treatment 7 DAT, efficacy was 92.4%; 14 DAT and 21 DAT it was 75.2% and 78.9%, and it dropped to below 60% at the end of the trial. The efficacy of clofentezine (39.4-68.2%) was unsatisfactory, which is probably the result of a resistance developing under high selection pressure of these compounds in the Morovic locality in preceding years, while the newly introduced acaricide spirodiclofen showed high and long-lasting efficacy (97.2%, 38 DAT). The results of the trials are discussed in terms of improving management of the populations of European red mite and pear psylla.

Resistance to chlorpyrifos and lambda-cyhalothrin along with detoxifying enzyme activities in field-collected female populations of European red mite

The levels of susceptibility of populations of the European red mite Panonychus ulmi (Koch) (Acarina: Tetranychidae) collected from apple orchards in the Bursa region of Turkey to the insecticides chlorpyrifos and lambda-cyhalothrin, were determined by a petri leaf disk—Potter spray tower method. When compared with the susceptible population, resistance ratios at the LC50 level ranged from 6.0- to 35.6-fold, and from 0.7- to 5.7-fold for chlorpyrifos and lambda-cyhalothrin, respectively. Kinetic parameters of general esterase activity with α-naphthyl acetate as substrate indicated that an increased activity was present in the resistant populations compared with the susceptible populations. In these strains, 1.5- and 2.2-fold higher Glutathione S-transferase (GST) activity was also detected with the substrate 1-chloro-2,4-dinitrobenzene. General esterase activity gel profiles of these populations were studied by native polyacrylamide gel electrophoresis, but no relationship between resistance ratios and band patterns was detected. The results of this study document a decreased efficacy of chlorpyrifos and lambda-cyhalothrin in field populations of P. ulmi in Turkey, possibly linked to altered activities of esterases and GST.

Manejo integrado de pragas em macieira no Rio Grande do Sul II: uso de Neoseiulus californicus para o controle de Panonychus ulmi

Com o objetivo de implementar o controle biológico de ácaro-vermelho Panonychus ulmi em macieira foi proposta uma estratégia de controle baseada na criação de Neoseiulus californicus em estufa, em liberações inundativas e no uso de acaricidas, em um pomar comercial de macieira da Rincão das Flores Agropastoril (Agriflor), em Vacaria, Rio Grande do Sul, entre 1992 e 1996. A amostragem do ácaro-vermelho orientou as liberações e as transferências de ácaros predadores, das estufas de criação e dos ramos provenientes da poda verde, para parcelas de alta incidência de ácaro-vermelho. A eficiência da estratégia de controle do ácaro-vermelho foi avaliada com o levantamento de ovos de inverno. No primeiro ano, a associação de acaricidas com ácaros predadores permitiu um reduzido número de ovos de inverno do ácaro-vermelho, em torno de 1,3 ovo por unidade de amostragem contra 59,8 ovos na testemunha. No segundo ano, 58% das macieiras não foram pulverizadas com acaricidas. Nos dois anos subseqüentes, o controle do ácaro-vermelho foi realizado exclusivamente com ácaros predadores. N. californicus passou o inverno nas ervas daninhas do pomar e migrou espontaneamente para a copa das macieiras nos anos subseqüentes a sua introdução.

Characterization of resistance to clofentezine in populations of European red mite from orchards in Ontario.

Resistance to clofentezine was identified in four populations of the European red mite, Panonychus ulmi (Koch), from apple orchards in Ontario after ca. 5 years use. Resistance was expressed at high levels (> 2000-fold at the LC 50) to clofentezine in a population selected in the laboratory. This population was resistant to hexythiazox and to the organotin compounds cyhexatin and fenbutatin-oxide. However, a population selected with fenbutatin-oxide did not show cross resistance to clofentezine. The clofentezine-resistant population was not resistant to pyridaben, propargite or dicofol. The synergists, piperonyl butoxide and DEF, were ineffective in overcoming the resistance. Resistance to clofentezine declined rapidly in a mixed population (most resistance was lost in fewer than three generations). There were several fitness factors (fewer eggs/female, longer egg stage, longer development time for males) associated with the resistant population which may have contributed to the loss of resistant phenotypes. However, in a second test in which selection was removed from a resistant population, resistance persisted for at least 10 generations. Observations on field populations indicated that resistance persisted for at least two seasons.

FIELD BIOASSAY METHODOLOGIES FOR THE DETECTION OF RESISTANCE TO ACARICIDES IN POPULATIONS OF EUROPEAN RED MITE (ACARI: TETRANYCHIDAE)

AbstractThe toxicity of dicofol, pyridaben, formetanate HCl, and abamectin to European red mite, Panonychus ulmi (Koch), was determined using either a Petri dish or leaf dip bioassay (as potential field assay procedures) and was compared with results from a standard laboratory procedure that requires a Potter spray tower to treat leaf disks. Abamectin and pyridaben were the most toxic acaricides tested, and dicofol and pyridaben were more toxic when applied to Petri dishes than to leaf disks. Formetanate HCl was the least toxic acaricide tested by either leaf disk or leaf dip procedures. Diagnostic concentrations of pyridaben were determined as 5 mg active ingredient per litre (a.i./L) with the Petri dish assay and 15 mg a.i./L with the leaf disk assay. Mortality of European red mites to pyridaben at diagnostic concentrations was consistently 100% with the leaf disk assay and > 90% with the Petri dish assay. Residues of pyridaben on Petri dishes stored at 4 °C in a refrigerator were stable for at least 21 d. For dicofol, both leaf disk and Petri dish assays gave similar results, and 25 mg a.i./L, previously used as the diagnostic concentration in the Petri dish assay, resulted in > 99% mortality of the standard susceptible strain. This technique identified resistant individuals in all of the field populations tested. Abamectin applied at 2 mg a.i./L to leaf disks consistently gave 98–100% mortality, but results at 2 mg a.i./L with the Petri dish assay gave variable results and this was not a reliable technique for monitoring resistance. Concentrations of formetanate HCl required for the leaf dip assay were too high to be useful in field assays; however, all populations of European red mite tested using the leaf disk assay appeared susceptible. For the ovicide, clofentezine, mortality of eggs tested by the leaf disk assay at 100 or 500 mg a.i./L ranged from 89 to 100%. Results with the leaf dip procedure, using a 350 mg a.i./L suspension consistently resulted in > 96% mortality of eggs from susceptible field populations. These procedures are a useful tool in the development of resistance management programs for acaricides used in integrated pest management (IPM) systems for tree fruits.

Influence of Selective Insecticides on Population Dynamics of European Red Mite (Acari: Tetranychidae), Apple Rust Mite (Acari: Eriophyidae), and Their Predator Amblyseius fallacies (Acari: Phytoseiidae) in Apple

The predaceous phytoseiid mite, Amblyseius falllacis (Garman), is important to the biological control of spider mites in deciduous fruit orchards. Insecticides applied for control of insect pests may be toxic to A. fallacis thereby causing spider mite outbreaks. Pyrethroids are highly toxic to A. fallacis and are not recommended for use after petal fall. Applications of pennethrin at pink and petal fall resulted in outbreaks of European red mites, Panonychus ulmi (Koch) because of the elimination of A. fallacis . Permethrin-treated trees had European red mite populations averaging 5 times higher than in untreated trees. Materials which conserved A. fallacis populations maintained European red mite below economic thresholds throughout the season. The apple rust mite, Aculus schlechtendali (Nalepa), served as an alternate food source for A. fallacis, particularly in trees which had low European red mite populations.

Population Dynamics of Amblyseius fallacies (Acari: Phytoseiidae) and European Red Mite (Acari: Tetranychidae) in Apple Trees Treated with Selected Acaricides

Experiments were conducted to evaluate the effects of early-scason ovicides, selective acaricides, horticultural oil, and potassium salts of fatty acids on the population dynamics of the phytoseiid predator Amblyseius fallacis (Garman) and its prey, the European red mite, Panonychus ulmi (Koch). Both ovicides prevented early-season European red mite outbreaks but only clofentezine-treated trees, with the help of A. fallacis, had low densities of European red mites throughout the entire season. However, treatment with clofentezine kcpt mites at subeconomic levels only if insecticide sprays did not disrupt predator mite populations. Two applications of permethrin drastically reduced natural enemies, and allowed European red mite outbreaks to occur. Selective acaricides varied in their effects on A. fallacies and European red mites. Although not significantly different from each other, all selective acaricides resulted in significantly fewer A. fallacis and European red mites than the untreated trees. Repeated applications of horticultural oils and M-Pede were required to reduce the European red mite populations and were no more effective in conserving predator mites than some of the selective acaricides.

Influence of European Red Mite on Leaf and Whole-canopy Carbon Dioxide Exchange, Yield, Fruit Size, Quality, and Return Cropping in `Starkrimson Delicious' Apple Trees

The hypothesis was tested that effects of late-season European Red Mite (ERM) [Panonychus ulmi (Koch)] injury on apple (Malus domestica Borkh.) fruit development are better explained by carbon physiology than by pest densities. Midseason ERM populations were allowed to develop in mature semi-dwarf `Starkrimson Delicious'/M26 trees with moderately heavy crops, then were controlled with miticides at different mite-day (activity of one mite per leaf for 1 day) levels as estimated by weekly leaf sampling. The range of final mite-days was from 250 to 2100 on individual trees. Seasonal fruit growth patterns were monitored. Diurnal whole-canopy net CO2 exchange rate (NCER) was measured in eight clear flexible balloon whole-canopy chambers on several dates before and after mite infestations. Mite injury reduced fruit growth rates. Leaf and whole-canopy NCER were reduced similarly. Late season fruit growth and final fruit size were correlated with accumulated mite-days, but were better correlated to whole-canopy NCER per fruit. Fruit firmness, color, soluble solids and starch ratings showed no correlation to mite-days. Number of flower clusters per tree and final fruit per tree the following year were not related to accumulated mite-days, but final fruit per tree the following year were better correlated to whole-canopy NCER per fruit. These results generally supported the hypothesis.

EFFECTS OF APPLICATION DATE ON THE PERSISTENCE OF CLOFENTEZINE RESIDUES: IMPLICATIONS FOR MANAGEMENT OF RESISTANCE IN THE EUROPEAN RED MITE

AbstractThe effects of timing of applications on the persistence of chemical and biologically active residues of clofentezine were tested on apple foliage during two seasons. Residues from prebloom and petal fall applications were less persistent than those in mid-season. Early season applications were toxic to European red mite for 7–21 days but mid-season applications were toxic for as long as 50–62 days. Chemical residue losses were also faster in the early season. Persistence of chemical residues was related to the rate of leaf growth and expansion. In 1991, foliage area expanded 244% per week during the prebloom period, 23% per week at petal fall, and 10% per week in July (mid-season).In a field test, applications of clofentezine at petal fall reduced European red mite populations within 7 days and mite numbers remained below economic thresholds for 6 weeks.

Management of Summer Populations of European Red Mite (Acari: Tetranychidae) on Apple with Horticultural Oil

A highly refined horticultural petroleum oil, Sunspray Ultra Fine, was evaluated in laboratory and field tests for efficacy against summer eggs and larvae of European red mite, Panonychus ulmi (Koch). Oil had significant ovicidal and residual larvicidal activity in dip treatments at rates as low as 0.00005%, but treatments using the same rates in a Potter spray tower caused less mortality. High-contact mortality of mite larvae sprayed in laboratory tests was obtained at rates of 0.25–1.00%. Field applications of oil by airblast sprayer were tested during the summer for their ability to suppress mite populations throughout the growing season. Effective control was achieved with three applications of oil at 3 and 2%, starting at the petal-fall stage and continuing on a 2–3-wk schedule. A rate of 1% provided control under conditions of moderate population pressure but required an additional spray in late July under severe population pressure. Rates of 0.25 and 0.05% resulted in unacceptable mite numbers by midsummer. Phytotoxicity caused by the oil was most severe at the higher rates, but oil caused no leaf drop even when trees were moisture-stressed. No effects of oil were seen on fruit finish or color, except for an increase in scarf skin of ‘Law Rome’ at the highest rates. High-pressure handgun oil sprays against a mixed population of mite eggs, immatures, and adults reduced motile forms by 79–95% at rates of ≥0.25%.

Toxicity of Flufenoxuron Alone and in Mixture with Alphacypermethrin or Fenbutatin Oxide to Tetranychus urticae and Panonychus ulmi (Acari: Tetranychidae)

Acaricidal activity of flufenoxuron alone and mixed with alphacypermethrin or fenbutatin oxide was evaluated in laboratory and field studies. In a laboratory study with the twospotted spider mite, Tetranychus urticae Koch, flufenoxuron alone and mixed with alphacypermethrin was highly effective against immature stages, but ineffective against eggs and nontoxic to adults. A mixture of flufenoxuron and fenbutatin oxide was effective against all stages of T. urticae. Flufenoxuron had no repellent activity, but flufenoxuron + alphacypermethrin exhibited strong repellency. In females treated as deutonymphs with flufenoxuron alone and mixed with alphacypermethrin, we observed substantial reduction in egg viability but there was no obvious effect on number of eggs laid. In a field study of a population of European red mite, Panonychus ulmi (Koch), and a population of T. urticae, efficacy of flufenoxuron and its mixtures, expressed as a protective value at 30 d in each treated plot relative to an untreated plot, was similar to that of the commonly used azocyclotin or hexythiazox. Based upon laboratory and field data, flufenoxuron or mixtures described may be used to prevent damage by P. ulmi and T. urticae.

WHOLE-TREE GAS EXCHANGE, MITE DAMAGE, AND FRUIT DEVELOPMENT IN APPLE.

This study examined the hypothesis that late-season European Red Mite (ERM) injury effects on fruit development are mediated via carbon relations of apple trees. ERM injury were allowed to develop in mature semi-dwarf `Starkrimson Delicious'/M26 trees with moderate crops (about 30 t/ha). Populations of ERM developed concurrently in all trees, but were controlled with miticides at different mite-day levels, giving a range of final mite-days from 300 to 2100 on individual trees as estimated by weekly leaf sampling for mites. At intervals through the season fruit growth was monitored. Diurnal whole tree photosynthesis was measured with eight clear flexible “balloon” whole tree chambers. Before the mite injury developed, fruit sizes were very similar, but in the last 60 days before harvest differences in fruit weights of up to about 50 grams were induced by mite injury which reduced whole tree photosynthesis comparably. The final fruit growth and size were well correlated with whole tree photosynthesis per fruit. Effects on other fruit quality factors were minor. These results suupport the hypothesis that whole tree source/sink balance may be an integrator of crop load and mite injury effects on fruit development. Fruit growth rates may be a practical monitor of the integrated effects of crop load and stresses.

Stability of Dicofol Resistance in Populations of European Red Mite (Acari: Tetranychidae) on Apples in Southern Ontario

Fluctuations in levels of resistance to dicofol in populations of European red mite, Panonychus ulmi (Koch), from several orchards with different frequencies of resistant individuals were compared with responses of laboratory colonies established from the same sites. Considerable variability in responses occurred in observations spaeed over 2 yr, but the frequency of dicofol-resistant individuals in these populations did not decline in the absence of selection pressure. Laboratory colonies reared through 32 generations displayed relatively constant resistance frequencies, suggesting that dicofol resistance is stable for a time equivalent to at least 3 yr in the field. Relative fecundities of mites resistant and susceptible to dicofol were examined by comparing the number of eggs laid by females from intra- and interstrain crosses, as well as the percentage hatchability, percentage survivorship, and sex ratio of the resulting progeny. Females from a 12-yr-old susceptible laboratory colony laid more eggs than females from a more recently established susceptible colony and than females from two colonies resistant to dicofoi. Resistant and susceptible mites did not differ for any of the other parameters examined. It is concluded that the absence of a reproductive detriment is a major factor in the apparent stability of resistance to dicofol in these mites. Implications of these findings for management of dicofol resistance in P. ulmi are discussed.

Temporal Variability in Repeated Bioassays of Field Populations of European Red Mite (Acari: Tetranychidae): Implications for Resistance Monitoring

Discriminating bioassaysare increasingly being used to detect resistance and estimate the frequency (F) of resistant (R) phenotypes in field populations. The proportion of survivors in discriminating bioassaysis thought to measure the frequency of R phenotypes in the population. External factors that cause physiological stress in a field population may alter response to a discriminating concentration and affect estimates of F. Because esusceptible (S) phenotypes already die at the discriminating concentration, only the response of R phenotypes changes. Thus, estimates of F will be biased and populations under stress will appear to be more susceptible than they really are. Repeated discriminating bioassays of the European red mite, Panonychus ulmi (Koch), showed variability in estimates of F. Repeated bioassays of P. ulmi from commercial apple orchards were used to construct a cumulative distribution function that describes the probability that Rphenotypes die in the discriminating bioassay. This distribution function was then used in simulations to explore the effect of day-to-day variability in tolerance of R phenotypes on resistance monitoring programs.

Hexythiazox Resistance in a Field Population of European Red Mite (Acari: Tetranychidae) on Apples

Laboratory and field tests conducted from 1985 to 1989 demonstrated that a population of European red mite, panonychus ulmi (Koch), in an apple orchard in Pennsylvania had become highly resistant to hexythiazox, a relatively new acaricide that is not registered for use on apples in the United States. A total of 20 treatments of hexythiazox had been applied to four different randomly selected trees throughout this 0.6-ha orchard during June and July from 1983 to 1986. Each year, 4-20 randomly selected trees were treated with two to five sprays of hexythiazox. In laboratory bioassays conducted in 1988 and 1989, mortality of overwintering eggs, summer eggs, and larvae averaged 98% of these life stages of mites from a susceptible population of mites collected from a research orchard in New York were killed at hexythiazox concentrations of > 100 ppm (AI) in laboratory tests. The mites from both the New York and Pennsylvania populations were susceptible in laboratory bioassays to clofentezine (another new, chemically unrelated miticide which is also primarily active against mite eggs and larvae) despite the fact that 12 sprays of clofentezine were applied to the Pennsylvania population from 1981 to 1986.

Stability of Cyhexatin Resistance in Field Populations of European Red Mite (Acari: Tetranychidae)

Two field populations of European red mite, Panonychus ulmi (Koch), that were resistant to cyhexatin were exposed for 2 yr to three different levels of selection pressure by cyhexatin to determine whether resistance was stable under field conditions. Populations of European red mites from field plots where pressure with cyhexatin was intensive, limited, or absent were periodically tested for susceptibility to cyhexatin residues with a 24-h leafless bioassay technique. By late in the second year, mites from the plot where no cyhexatin had been applied were as susceptible to cyhexatin in bioassay as mites from the intensively treated plot. After at least 10 generations without selection pressure, the frequency of mites that were phenotypically resistant to cyhexatin appeared to be stable in these populations.

Relationship Between Field Efficacy and Laboratory Estimates of Susceptibility to Cyhexatin in Populations of European Red Mite (Acari: Tetranychidae)

The relationship between field and laboratory estimates of susceptibility to cyhexatin was studied for 2 yr in populations of European red mite (ERM), Panonychus ulmi (Koch), in commercial apple orchards. Field efficacy, expressed as reduction in cumulative mite-days in treated plots relative to untreated plots, was compared with mortality of field-collected ERM exposed to cyhexatin residues in 24-h leafless bioassays. In 1986, population susceptibility to cyhexatin based on two early-season applications in field trials was similar to that derived from laboratory bioassays for 12 of the 14 orchard populations that were assessed. In 1987, bioassay response of six orchard populations was compared with the efficacy of one versus two cyhexatin applications and with early-season versus summer applications of cyhexatin. Population susceptibility as determined by efficacy of early-season treatments was in agreement with susceptibility in bioassay for four of six populations tested. Summer treatments were less effective than early-season treatments and did not reflect bioassay estimates of susceptibility as well as early-season treatments did. Control was better than expected in several cases. It was concluded that predictions of field efficacy cannot be based on laboratory bioassays alone; mite population dynamics and operational factors related to the cyhexatin application and orchard management also must be considered.

Activity of Clofentezine Against European Red Mite (Acari: Tetranychidae)

The ovicidal and larvicidal activity of clofentezine against a population of European red mite (ERM), Panonychus ulmi (Koch), was evaluated in laboratory bioassays and compared with activity of hexythiazox. Clofentezine was more active against summer than winter eggs of ERM; LC50 values of eggs in an early developmental stage differed by 11 times (1.01 and 11.1 ppm, respectively). Eggs of either type were significantly less susceptible to clofentezine when treated the day before hatch than when treated at earlier developmental stages (P < 0.02). When exposed to leaves treated with 10-100 ppm clofentezine, mortality was high among larvae but negligible among nymphs and adults. The amount of clofentezine required to kill 50% of winter or summer eggs was half that of hexythiazox. Winter eggs surveyed from 31 commercial apple orchards in three regions of New York did not vary significantly (P = 0.11) in susceptibility to clofentezine at a concentration of 100 ppm, but eggs from Champlain Valley orchards were less susceptible than those from the Hudson Valley or Wayne County when tested at 10 ppm (P = 0.0003).

Effects of two sterol-inhibiting fungicides on populations of pest and beneficial arthropods on apple

This research demonstrated that sterol-inhibiting fungicides alter the population structure of some pest and beneficial arthropods in apple orchards. Orchard populations of European red mite, Panonychus ulmi (Koch) (Acarina: Tetranychidae); the predacious mite, Typhlodromus caudiglans Schuster (Acarina: Phytoseiidae); the spotted tentiform leafminer, Phyllonorycter blancardella Fabr. (Lepidoptera: Gracillariidae); the leafminer parasite Pholetesor ornigis Weed (Hymenoptera: Braconidae); the green apple aphid, Aphis pomi DeGeer (Homoptera: Aphididae); white apple leafhopper, Typhlocyba pomaria McAtee (Homoptera: Cicadellidae); Campylomma verbasci Meyer (Hemiptera: Miridae); chalcids, primarily Sympiesis sericeicornis Nees (Hymenoptera: Chalcididae), were monitored for two growing seasons in a McIntosh apple orchard that had received applications, at 2-week intervals, of two sterol-inhibiting fungicides, bitertanol and flusilazole. High rates of flusilazole were associated with increased numbers of European red mite and decreased numbers of predacious mite species, particularly T. caudiglans. Trees receiving a high rate of bitertanol had fewer European red mites and predacious mite species. Fungicides did not influence spotted tentiform leafminer oviposition or the number of leafminer larvae in May and June 1985. However, in September 1985 there were fewer leafminer pupae in plots treated with the two lower rates of flusilazole and more larvae in plots treated with the high rate of bitertanol, relative to trees sprayed with captan. In 1986, there were more leafminer eggs in plots treated with the low rate of bitertanol compared with captan and non-sprayed trees. However, by 24 June, all treatments showed similar levels of leafminer larvae and pupae. Populations of P. ornigis were generally higher in trees treated with flusilazole in both years. Numbers of aphids and mullein bug were higher in trees treated with flusilazole relative to non-sprayed and captan-treated trees. Chalcid populations were higher in bitertanol-treated trees. Fungicides had no apparent effect on populations of white apple leafhopper.