INCREASING THE HARMFULNESS OF THE ERIOPHYOID MITE ACULUS SCHLECHTENDALI (NALEPA), A PHYTOPARASITE OF APPLE TREE IN THE NON-BLACK EARTH ZONE OF RUSSIA

Apple rusty mite Aculus schlechtendali (Nalepa) (Eriophyidae) is an invasive parasite in the Central region of the Non-Black Earth Zone of Russia. At the beginning of the XXI century, there were only small foci of the phytoparasite, but at present it is widespread almost everywhere, periodically giving a massive outbreak of reproduction. The number of mites reaches 1000 and more mobile individuals per 1 leaf (25.5 per 1 cm2). The body is microscopic (160–175 microns), so it is very difficult to be detected. Also, with a small number of A. schlechtendali, symptoms of plant infection do not appear outwardly, which allows the active spread of the mite with planting or other plant material. To count the number of the parasite in the spring, the tops of annual growths up to 10 cm long were sampled at 10 discount sites (in order to view opening buds), and during the vegetation, 10 leaves (4-5th leaves from the top of the sprout) were taken from each discount site. Selected samples of buds and leaves were examined under an MBS-10 binocular microscope. A. schlechtendali is especially dangerous in nurseries and young fruiting plantations of apple trees; it feeds not only on leaves (from the underside) and young sprouts, but damages flowers and buds of the apple tree. Effective control of the parasite requires constant monitoring and strict quality control of the planting material.

Abundance and distribution of Aculus schlechtendali on apple orchards in Southern of Brazil

The dispersion of insects and mites can be favored by many factors, including the increasing circulation of plant materials. Special attention is needed to the eriophyoid mites, which have a greater potential as introduced species, due to their physical and biological characteristics. Aculus schlechtendali (Nalepa) (Eriophyidae, Apple Rust Mite - ARM) is considered an important apple pest in several countries, being recently reported for the first time in Brazil. This study aimed to carry out a survey of the abundance and distribution of ARM in the Southern region of Brazil, in the cultivars Fuji, Gala and Eva, grown in the states of Rio Grande do Sul (RS), Santa Catarina (SC) and Paraná (PR). In addition, Moran's I autocorrelation was used as an analytical tool to assess the spatial dependence between the sample points. A total of 94 orchards were sampled in 19 municipalities, distributed in the three evaluated states. Regarding cultivars, there were 40 orchards of Fuji cultivar, 43 of Gala and 11 of Eva. At each one, 20 plants were selected, from which four leaves were collected, totaling 80 leaves/orchard. The screening and identification of the mites occurred at the Laboratório de Acarologia at the Universidade do Vale do Taquari – Univates, and the statistical analysis were made using generalized linear mixed models with subsequent paired analysis, using R-software. A total of 1,647 specimens of ARM were found in 66 orchards located in 17 municipalities, with an average number (mean ± standard deviation) of 24 ± 55 mites/orchard, 44 ± 83 in Fuji, 10 ± 19 in Gala and 17 ± 21 in Eva. The average number of mites differed between cultivars and states, with the lowest number in the cultivar Gala and in Rio Grande do Sul. No spatial autocorrelation was observed between the points, indicating that the dispersion of ARM in Southern Brazil has occurred at random, without a predefined pattern that would indicate a possible hotspot. The presence of this species serves as an alert for the apple production industry, regarding the distribution of a species previously not reported in the region. The recognition of the presence, abundance and distribution of this species will help in the monitoring and future management decisions, as well as the understanding of the distribution pattern.

Effects of Aculus schlechtendali (Acari: Eriophyidae) population densities on Golden Delicious apple production

Field trials were carried out in order to evaluate the seasonal abundance and the impact on yields of the Apple Rust Mite (ARM) Aculus schlechtendali (Acari: Eriophyidae) in an experimental fruit orchard located in northern Italy (Trentino region). The effect of ARM on yield and market quality parameters were assessed on Golden Delicious apple fruits. Fruit size, fruit weight, round colour hue, presence of russet as well as inside quality, i.e. soluble solids, acidity and Perlim index, were evaluated over two seasons considering three population levels of ARM that were determined applying different pesticide strategies. Effects of rust mites on return bloom and yield efficiency were also evaluated. ARM seasonal abundance showed a peak in mid-summer. Relationships between ARM and predatory mites were weak. Moderate to high ARM densities affected fruits size, fruit weight, and round colour hue of Golden Delicious fruits. In contrast, ARM populations did not affect russet on fruits, return bloom and yield efficiency. Additional studies were conducted in the laboratory, on detached Golden Delicious apple leaves, to evaluate the potential for population increase at temperatures close to those recorded in field conditions. These studies evidenced a high potential for population increase.

Occurrence of the quarantine mite pest Aculus schlechtendali (Acari: Eriophyidae) in apple orchards of Serra Gaúcha, Rio Grande do Sul state, Brazil

The aim of this work is to report the presence of Aculus schlechtendali (Nalepa, 1890) (Prostigmata: Eriophyidae) (Apple rust mite—ARM), in apple orchards of Serra Gaúcha, state of Rio Grande do Sul, Brazil. Surveys were conducted from apple leaves of Gala cultivar in a commercial orchard of Vacaria County (S 28' 34.540 W 050' 52.153) in the Northeast region of the state of Rio Grande do Sul, between November 2016 and January of 2017. The morphological traits and the relative measurements matched with those of A. schlechtendali. This is the first report of this mite pest in Brazil, so far regulated as a quarantine pest, and the third country report in South America. Consideration on the potential pest status of ARM is discussed.

Modeling the mite counts having overdispersion and excess values ofzero using zero-inflated generalized poisson regression

The aim of this study was to apply for zero-inflated generalized Poisson regression in the modelling of mite counts that include excess values of zero and overdispersion. The results of, as mean regression, overdispersion and zero-inflated regression, were determined in three stages. It was obtained that 33.33% (120 observations) of the total numbers of mite taken as a dependent variable to model had zero values. The overdispersion parameter range was detected to be quite high. It was determined that zero-inflated data and overdispersion had an important effect on mite counts (P less than 0.01). The effects of region, month, year, varieties, temperature and humidity were found to be statistically significant on mite counts (P less than 0.01). The number of eggs found in harmful mites (Aculus schlechtendali) in the Starking variety was relatively higher than in the Golden variety. The results displayed that the differences among regions and varieties regarding the number of eggs found in harmful mites were statistically significant (P less than .01).

Aculus schlechtendali. [Distribution Map].

A new distribution map is provided for Aculus schlechtendali (Nalepa). Acari: Eriophyidae. Hosts: apple (Malus domestica), European pear (Pyrus communis) and crab-apple tree (Malus sylvestris). Information is given on the geographical distribution in Europe (Austria, Belgium, Bulgaria, Croatia, Denmark, Finland, France (Mainland France), Germany, Greece (Mainland Greece), Hungary, Italy (Mainland Italy), Lithuania, Netherlands, Norway, Poland, Portugal, Russia (Central Russia, Southern Russia), Serbia, Slovenia, Sweden, Switzerland, UK (England and Wales, Northern Ireland), Ukraine), Asia (China (Gansu, Sichuan), Japan (Honshu), Lebanon, Pakistan), Africa (Egypt), North America (Canada (British Columbia, New Brunswick, Nova Scotia, Ontario, Quebec), USA (California, Indiana, Massachusetts, Michigan, New Jersey, New York, Ohio, Oregon, Pennsylvania, Utah, Vermont, Virginia, Washington, Wisconsin)), South America (Chile), Oceania (Australia (Tasmania), New Zealand).