[EBOOK] Citrus Mites (Identification, Bionomy and Control), Vincenzo Vacante (Professor of General and Applied Entomology Department OASI, Mediterranean University Reggio Calabria, Italy), Published by CABI

An exhaustive treatment of injurious mites associated with economic plants gives rise to the necessity, according to the large number of species involved and their particular bionomics, of an organic presentation divided into systematic categories and individual crops. This would facilitate the presentation of the subject and avoids the consolidated and reprehensible practice, which tends to simplify, either for convenience or opportunism, the problem of mites injurious to citrus in regard to the small number of traditionally known species, legitimizing inappropriate phytoiatric choices on the basis of decisions based on macroscopic examination and/or the colour of an organism rather than on more scientific parameters (morphological, biological, etc.), to the economic, toxicological and ecological detriment of the entire field and societies that directly or indirectly enter into a physical relationship with farming and/or its products.

The present work is the result of this reflection and aims to assess the problem of injurious mites associated with citrus in the world. The work basically consists of a bibliographical research of the phytophagous mites recorded on citrus throughout the world, integrated with the author's knowledge. Various researchers (Quayle, 1938; Bodenheimer, 1951; Ebeling, 1959; Chapot and Delucchi, 1964; Talhouk, 1975; Jeppson, 1978, 1989; Smith and Pena, 2002) have briefly dealt with the subject on both a regional and global scale. The list of species associated with citrus in southern California published by McGregor (1956) is well known, together with those of Muma (1975) for Florida, Vacante et al. (1989) for the Mediterranean area and Dhooria et al. (2005) for India. A more organic work was published by Jeppson et 111. (1975), who outlined a global picture of the problem of mites injurious to different economic plants and illustrated with a wealth of details the case of citrus. Recently, Gerson (2003) presented a list of species known for citrus throughout the world. However, an updated work in the field is required that is able suitably to guide personnel (researchers, technicians and managers of phytopathological departments) interested in the problem of citrus mites. In total 104 species ascribed to the Phytoptidae Murray, Eriophyidae Nalepa, Diptilomiopidae Keifer, Tarsonemidae Kramer, Tenuipalpidae Berlese, Tuck-erellidae Baker et Pritchard and Tetranychidae Donnadieu families were treated. All species quoted are formally phytophagous, although a number of them pose no problem to citrus groves (Bryobiinae, some Tuckerellidae and Tetranychidae and Eriophyidae) and were included in the list of injurious mites for completeness and out of respect for the bibliographical information. However, treatment of these latter species allows for the discrimination of mites that occasionally infest citrus from those that are potentially or realistically harmful, assisting the work of phytosanitary services.

The book presents the fundamental elements of the external morphology of the mites with the aim of providing a tool that helps in then identification, of the high systematics of the species dealt with and the means and methods of collecting mites from plants and substrate, together with their preservation and preparation for study. The structure of the mouthparts of mites is briefly dealt with to introduce the fundamental aspects of symptomatology and damage.

A key is presented for the identification of the basic systematic categories (families, subfamilies, tribes, genera) and species, brief information on the morphology and systematics of each category, the main elements of morphology and bionomics (geographical distribution, bio-ecology, natural enemies, symptomatology and damage) of the different species. The morphological description of each species is mostly correlated by original black and white drawings produced at the time by the various authors and, where possible, information is given about web sites (Table 4.1) where the natural colours and features of leaving injurious mites and their damages on citrus can be observed.

Under no circumstances did the author discuss the merits of decisions of a taxonomical nature. Morphological descriptions of the various species were dealt with by the contributions of specialists; generally they are reported exactly and in some cases were simplified and adapted to the needs of the text. The information on natural enemies mainly regards the species collected on citrus, or introduced into this crop from other regions and/or investigated for the control of injurious mites. Among these, Phytoseiidae mites represent the greatest number of species, according to the catalogue of de Moraes et ill. (2004). This choice does not involve any position of the author on their taxonomic status but only the attempt towards a given minimum order to the discussion, resulting in the ideas of different specialists on the systematics of Phytoseiidae mites being an open problem. Symptoma-tology and damage are reported only in the case of sufficient certainty, supported by appropriate bibliographic references. In any case, for each family, several tables are presented summarizing the pest status and geographical distribution of each species.

For each species a paragraph on control examines the chemical and biological means and the control strategies (chemical, biological and integrated pest management) available in the different regions of the world.

The information given is taken from the official bibliography and where possible has been integrated with the author's experience. In this respect, the information on acaricides refers to their chemical groups in order to avoid giving information exceeded by the rapid evolution of the market and/or licence to use, commonly distinct by the withdrawal of various substances from the market and the entry of other substances. The suggested data do not have a general relevance, since the use of various acaricides is subject to the laws of individual countries. It is therefore the responsibility of the reader to verify their applicability in different regions.

The complexity of the subject and the considerable physical dimensions of the citrus crop, spread throughout the subtropical and tropical regions of the world, do not facilitate its treatment and make reference to ecological, horticultural and socio-economic aspects, which often differ from one another. In this context, environmental factors are very important and may directly influence the bio-ecology of the different species and require strategic choices, which may vary from one region to the next for the same species, as in the citrus rust mite, Pliyllocoptrutn oleivora (Ashmead), which is the most important phytophagous mite pest in the warm and humid areas of Florida, together with the Texas citrus mite, Eutetranychus banksi (McGregor), while the citrus bud mite, Aceria sheldoni (Ewing), is not an economic problem; on the other hand, in the warm and arid areas of California, the citrus red mite, Panonychus citri (McGregor), is the most feared followed by A. stiel-dotti and Pil. oleivora and is an economic problem onlv in coastal areas (Childers et al., 1996). Similar situations have occurred in Mediterranean areas and in other humid regions of the world for the pink citrus rust mite, Aculops petekassi (Keifer).

Of equal importance are the productive choices, which vary between regions and continents. Indeed, the control of pests of products destined for fresh consumption generally requires more interventions than that designated for processing. With the former, cosmetic appearance is a priority, while with the latter, the development and abscission of the fruit are unaffected until 50-75% of the surface of the fruit is damaged (Allen and Stamper, 1979). As a result, production in Florida destined for the fresh market is treated with plant protection products three to four times a year, compared with up to two treatments for that designated for processing, with one petroleum oil and one acaricide treatment (McCoy, 1985; Browning, 1992). From this point of view, Mediterranean citrus crops, fundamentally directed at satisfying the needs of a market orientated towards fresh consumption, is considerably different from that of the USA and is therefore different in terms of control strategies.

The FAO (FAOSTAT, 2008) estimated for citrus a disparity in yield values (hectogram/ha) between different regions of the world, linked to various environmental and socio-economic causes, including variable availability of technical means and appropriate knowledge and/or specializations in the various fields of agricultural production. From this point of view, the knowledge of biotic adversities of crops and fruits helps to optimize quality and improve yield. In India, more than 30% of citrus production is lost every year as a result of damage by insect and mite pests (Pruthi and Mani, 1945; Butani, 1979a, b).

The above-mentioned facts may influence the agrarian economy of a region and do not allow for generalizations. Indeed, control of Pit. oleivora in Florida requires an annual expenditure of between 75 and 100 million dollars (McCoy, 1996b), while it poses no problem in other important citrus areas such as Italy where it is not present. Equally important is the case of the reddish black flat mite, Brevipalpus phoenicis (Geijskes), responsible for the transmission in the American continent of 'Lepra esplosiva' or 'Leprosis' (Childers et ill., 2001, 2003b), a feared viral disease (CiLV), prevention of which costs approximately 100 million dollars per year in Brazil alone (Rodrigues et al.f 2003) but which is non-existent and does not spread from the mite in the Mediterranean region. In lemon groves in Italy and Spam, up to three acari-cide treatments are carried out annually with a cost per hectare of approximately 450 per treatment. The control may have toxicological and ecological consequences, as in the case of the use of dithiocarbamates, aldicarb or other substances, whose social cost is difficult to quantify.

In conclusion, it is likely that in some cases the abnormality of the adaptations of one or more species may have escaped our attention, in which case we offer our apologies and willingness to compare with other authors involved in the subject who would like to contribute with their suggestions to improve this work.
Vincenzo Vacante

Reggio Calabria, May 2009

[EBOOK] Citrus Mites (Identification, Bionomy and Control), Vincenzo Vacante (Professor of General and Applied Entomology Department OASI, Mediterranean University Reggio Calabria, Italy), Published by CABI

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