Apple Rust Research Articles

The Flowering Crabapple — A Tree for all Seasons

Flowering crabapples are outstanding small trees for the landscape provided diseases are kept under control or avoided through the planting of disease resistant species and cultivars. Control measures for apple scab, fireblight, cedar apple rust and powdery mildew are listed along with descriptions of 25 flowering crabapples with good disease resistant properties. The height, habit, flower, foliage and fruiting characteristics are given for each type along with landscape use.

Effect of the Rain on Occurrence of Apple Rust

Effect of the Rain on Occurrence of Apple Rust

Basitac (Mepronil), a Promising Agent for Preventing Basidiospore Production by Galls of Japanese Apple Rust (Gymnosporangium yamadae) on Junipers

Basitac (Mepronil), a Promising Agent for Preventing Basidiospore Production by Galls of Japanese Apple Rust (<I>Gymnosporangium yamadae</I>) on Junipers

‘Liberty’ Apple1

Abstract ‘Liberty,’ which was tested under the number NY55140-19 is a good quality red apple that can be grown without fungicidal sprays in New York State (3). It is highly resistant to Venturia inaequalis (Cke.) Wint., apple scab, and to Gymnosporangium juniperivirginianae (Schw.), cedar apple rust and resistant to Podosphaera leucotricha (E. &amp; E) Salm, apple powdery mildew, and Erwinia amylovora (Burrill) Bergey et al, fire blight.

Apple, Miticide Evaluation Experiment, 1978

Abstract All acaricide treatments and the water control were applied in a manner to duplicate the alternate-row application technique employed by many commercial growers. A Swanson airblast sprayer, calibrated to deliver 25 gal/acre (94.64 liter/ha) at 100 psi (7.03 kg/cm2) at a ground speed of 2 mph (3.22 km/hr) when spraying one side of the row, was used to apply all materials on each spray date. Each plot consisted of a single row of 35 trees of 8-yr-old Red Del icious. Samples for the Plictran standard included in the tables were taken from similar adjacent trees in the remainder of the 4-acre block. Four subsamples of 25 leaves collected from each of 4 trees, spaced evenly along the treatment row were collected in plastic bags, placed in an ice chest, and taken to the laboratory where they were brushed following the Henderson-McBurnie method. Counts of European red mites, European red mite eggs, and Apple rust mites were recorded. Two applicationsweremade, the first on Jul 16 to the south side ofthe row and the second on Jul 28 to the north side. Countswere madeon Jul 15, 18, 25, 28, and 29. Data are presented as percent change between the two counting dates indicated in each table. The average number of mites or mite eggs is also included to give relevance to the percentages. No phytotoxic effects were noted.

Apple, Acaricide Test, 1978

Abstract Tests were conducted on 14-yr-old apple trees, cultivars Red Delicious, Sungold, and Stayman. Single-tree plots, 1 of each variety, arranged in randomized block design, were sprayed to runoff using a hydraulic sprayer equipped with a hand gun. All treatments were applied at a rate of 8 to 10 gal/tree and 400 psi. Miticides were applied on Jul 19 (Table 1) or Aug 8 (Table 2). Those trees used in the latter tests were treated every 2 wk throughout the season w ith Pydrin 2.4 lb/gal, 0.05 lb ai/100 gal; as a result, no predators were present. Mite population estimates were made by randomly picking 25 leaves/replicate, pooling the leaves for each replicate, then brushing the mites onto glass plates and counting all stages. Egg counts of the European red mite and the apple rust mite are not included in the tables. Pretreatment counts (not listed) were found not to be statisticallydifferent. The data were transformed to logarithms before analysis of variance and comparisons of means.

Field and Laboratory Evaluations of Fenvalerate Against Several Insect and Mite Pests of Apple and Pear in Oregon1

The synthetic pyrethroid fenvalerate was laboratory and field tested against several insect and mite pests of pome fruit crops in Oregon. This chemical gave superior pre-, and postbloom control of pear psylla, Psylla pyricola Foerster, adults and nymphs at rates of ca. O.4kg AI/ha when compared to a number of other experimental and registered insecticides in seasonal programs. Fenvalerate was also effective against codling moth, Laspeyresia pomonella (L.), on apples, had little effect on apple rust mite, Aculus schlectendali (Nalepa), was destructive to the predatory phytoseid Typholdromus pryi Scheuten, and was found to cause resurgences in densities of the European red mite, Panonychus ulmi (Koch).

Erratum: Teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae: a regression model of temperature and time effects

The influence of temperature on teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae was studied in vitro. Teliospores germinated from 8 to 30 °C. Germination w...

Gymnosporangium yamadae . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Gymnosporangium yamadae . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Aecia on apple ( Malus sylvestris ) and other Malus spp. Telia on Juniperus chinensis . DISEASE: Japanese apple rust. Aecia on leaves rarely on stems and fruit. Telia on globoid swellings or galls of juniper. GEOGRAPHICAL DISTRIBUTION: Japan, Korea, China.

Gymnosporangium juniperi-virginianae . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Gymnosporangium juniperi-virginianae . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Aecia on apple ( Malus sylvestris ) and crab apple ( Malus sp.). Telia on Juniperus virginiana and related species of the ' sabina ' group. DISEASE: American apple rust. Aecia chiefly on the leaves but also on stems and fruit. Telia on globoid or kidney-shaped galls of juniper. GEOGRAPHICAL DISTRIBUTION: Widespread in the USA east of the Rockies, also in California, Ontario and Quebec (CMI Map 61, ed. 2, 1965).

Gymnosporangium tremelloides . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Gymnosporangium tremelloides . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Aecia chiefly on apple ( Malus sylvestris ) and Sorbus , also on other Malus spp. and quince ( Cydonia vulgaris ). Telia on Juniperis communis and other species of the ' oxycedrus ' group. DISEASE: European apple rust. Aecia on leaves. Juniper gall rust, telia on fusiform or gall-like swellings of the smaller branches of juniper ( Juniperus communis ) or on hemispheric swellings along the sides of large branches. GEOGRAPHICAL DISTRIBUTION: Widely distributed in Europe (but not in Britain) and extending into N.W. Africa. Also in China and in western N. America from Alaska to Colorado and Utah.

Teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae: a regression model of temperature and time effects

The influence of temperature on teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae was studied in vitro. Teliospores germinated from 8 to 30 °C. Germination was first observed after 2 h from 12–28 °C but longer periods were required at lower temperatures. Promycelia formed basidiospores by 4 h from 12 to 24 °C but not until 7 h at 8 °C. Abortive germination of teliospores, without production of basidiospores, occurred from 26 to 30 °C. No germination was observed from 2 to 6 °C. Multiple regression analyses were performed and an equation relating germination of teliospores to temperature and time was formulated.

Fine structure of basidiospores of the cedar-apple rust fungus Gymnosporangium juniperi-virginianae

Each basidiospore of Gymnosporangium juniperi-virginianae contains many ribosomes as well as lipid droplets, mitochondria, small vesicles, endoplasmic reticula, and structures thought to be microbodies. Mature spores are either uninucleate or binucleate although larger, tetranucleate spores were occasionally observed. The spore wall appears as a thin layer except around the hilar region where two layers are evident. Germination is almost always lateral although no germ pore region was noted in the wall. Vacuolation takes place during germination and lipid bodies disappear. The wall of the germ tube arising from the spore is continuous with that of the spore. A large number of vesicles is present in the germ tube. Basidiospores may also germinate by repetition.

Effect of leaf age and inoculum concentration on the symptoms produced by Gymnosporangiumjuniperi‐virginianae on apple

SUMMARY Gymnosporangium juniperi‐virginianae, the incitant of cedar apple rust, induced the greatest number of lesions (flecks, pycnial lesions, aecial lesions) on 6‐ and 8‐day‐old leaves of single‐shoot potted apple plants inoculated and incubated under controlled conditions. The largest pycnial lesions developed on 2‐ and 4‐day‐old leaves and the largest aecial lesions on 6‐day‐old leaves. The number of lesions was positively correlated with the concentration of basidiospores in the inoculum, but lesion size was constant at different inoculum levels. Elevated inoculum concentrations failed to induce pycnia on cv. McIntosh which normally bears only flecks; very low concentrations induced the development of pycnia but not aecia on cv. Rome Beauty, which normally bears aecia. An ‘infection rating’, log10 (10 nd2), where n is the highest number of pycnial lesions per leaf and d is the largest mean diameter of pycnial lesions on any leaf, calculated for four cultivars in greenhouse tests showed a positive correlation with a ‘susceptibility rating’ developed from observations of natural infection of these cultivars in the field.

Fine structure of teliospores of the cedar-apple rust Gymnosporangium juniperi-virginianae

Teliospores of the cedar-apple rust Gymnosporangium juniperi-virginianae were examined using transmission electron microscopy. Each ellipsoid spore is divided into two cells by a transverse septum. A second septum separates the basal cell of the teliospore from a long, hyaline, cylindrical pedicel. The fine structure of these septa is considered. The cytoplasm of the teliospore is very dense and contains a complement of cellular structures including ribosomes, vacuoles, mitochondria, and a large number of structures thought to be lipid bodies. Each cell of the teliospore contains a single nucleus, in which the chromatin is often considerably condensed. Two germ pore regions are present in each cell. The spore wall is thinnest in these regions and is different in structure than elsewhere around the spore.

NOTES ON THE BIOLOGY OF THE APPLE RUST MITE, ACULUS SCHLECHTENDALI (PROSTIGMATA: ERIOPHYOIDAE), AND ITS DENSITY ON SEVERAL CULTIVARS OF APPLE IN NOVA SCOTIA

AbstractThe apple rust mite, Aculus schlechtendali (Nal.), is active on the apple leaves from late May until early August and passes through three generations as indicated by the peak numbers of eggs. This species overwinters as deutogynes under bud scales and crevices in the bark. During the latter part of May the deutogynes lay eggs that develop into first generation primaries, followed by a second generation the latter part of June. Eggs laid by the second generation primaries produce the overwintering deutogynes. Injury to the leaves, mainly bronzing to the ventral surfaces, becomes noticeable early in July. The numbers of A. schlechtendali varied between cultivars within orchards. The differences were not consistent between orchards.

Studies on the Integrated Control of Spider Mites on Apples in Oregon's Hood River Valley 1

A predaceous mite, Typhlodromus occidentalis Nesbitt (Acarina: Phytoseiidae), was incapable of maintaining population densities of the twospotted spider mite, Tetranychus urticae Koch, and McDaniel spider mite, T. mcdanieli McGregor, beneath levels that produced foliage injury on apples. T. occidentalis was an effective predator early in the season, but it was unable to maintain itself in sufficient numbers during early summer to prevent strong resurgences of twospotted spider and McDaniel spider mites during –September. By employing selective pesticides in commercial orchards, predatory mites can be maintained and can exert effective late-season control of tetranychid spider mites during August–October. One or more summer applications of selective acaricides which result in a more favorable predator:prey ratio is required to insure effective late-season predation by T. occidentalis. The cyclical nature of the predator:prey relationship may be due to lack of an alternate prey species such as the apple rust mite, Aculus schlechtendali (Nalepa), which is virtually absent in commercial orchards. Attempts to establish the apple rust mite as an alternate prey for T. occidentalis by deleting fungicidal applications for 3 years in 1 orchard were unsuccessful.

PLICTRAN AS AN ORCHARD ACARICIDE IN BRITISH COLUMBIA

AbstractPlictran (tricyclohexyltin hydroxide) was very effective against the European red mite, Panonychus ulmi (Koch), and the apple rust mite, Aculus schlechtendali (Nalepa), when applied at the pink bud stage of apple bud development. Plictran as a summer spray was not so effective because a small number of phytophagous mites survived. Plictran, however, is low in toxicity to the predaceous phytoseiids Metaseiulus occidentalis (Nesbitt) and Typhloseiopsis sp. near arboreus (Chant), and these predators increased on the surviving phytophagous mites. Because of this selective action, Plictran is a very promising acaricide for use in integrated mite control programs.

Insecticides for Codling Moth Control and Their Effect on Other Insects and Mites of Apple in British Columbia1

Several insecticides were evaluated in 1968 and 1969 for control of the codling moth, J. aspeyreesia pomonella (L.), and their effects on white apple leafhopper, Typhlocybapomaria McAtee; apple aphid, Aphis pomi De Geer; and the following mite species: European red mite, Panonychus ulmi (Koch); McDanicl spider mite, Tetmnychus medanieli McGregor; apple rust mite, Aculus schlechtendali (Nalepa); and the phytoselid Metaseiulus occiderztalis (Neshitt). Diazinon, diazinon + Superior oil, and Lannate® ( S -methyl N- [(methylcarbamoyl) oxy] thioacetimidate) did not give adequate control of the codling moth, but they were effective against the white apple leafhopper and apple aphid. The materials were not toxic to predaceous phytoseiid mites, and no increases in phytophagous species were noted. Phosalone and Gardona® (2-chloro-1-(2,4,5 trichlorophenyl) vinyl dimethyl phosphate) gave very good control of the codling moth and white apple leafhopper and suppressed the apple aphid. Phosalone did not cause an increase in phytophagous mites and was not toxic to predaceous phytoseiids. Gardona-sprayed trees showed damaging numbers of European red mite. McDaniel spider mite, and apple rust mite. Although predaceous phyto-seiids were reduced in the early season on Ganlona plots, they increased by late August. Toxicity to predaceous mites does not seem to account for the rapid increase of phytophagous mites on apple trees sprayed with this insecticide.

Integrated Chemical Control of Insects and Biological Control of Mites on Apple in Washington1

The predaceous mite Typhlodromus occidentalis Nesbitt (Acarina: Phytoseiidae ) was found to survive applications of several insecticides, fungicides, and horticultural sprays used on apple in Washington. A program which integrates the chemical control of insects with the biological control of mites has been established by selecting those chemicals which conserve T. occidentalis . The primary goal of the integrated program was the control of the McDaniel spider mite, Tetranychus mcdanieli McGregor (Tetranychidae), by Typhlodromus occidentalis . If Telranychus mcdanieli was the only food present for the predator, a cyclic predator: prey response developed. If the apple rust mite, Aculus schlechtendali (Nalepa) (Eriophyidae), was available, Typhlodromus occidentalis fed on it, but did not control this species. Under the latter conditions Tetranychus mcdanieli rarely became numerous. Populations of the European red mite, Panonychus ulmi (Koch) (Tetranychidae), were reduced by chemicals in the early part of the season and predation by Typhlodromus occidentalis prevented a later resurgence of populations of this species.