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# Chemical Control of Eucalyptus Rust: Brazilian Experiences

By Marcus Vinicius Masson, Willian Bucker Moraes and Edson Luiz Furtado

Submitted: November 27th 2011Reviewed: March 5th 2013Published: May 15th 2013

DOI: 10.5772/56319

## 1. Introduction

Eucalyptus (Eucalyptusspp.) naturally occurs in Australia, Indonesia and neighboring islands such as Flores, Alor and Wetar. The genus Eucalyptusbelongs to the Myrtaceae family, with around 600 species and sub-species, and shows high plasticity and worldwide dispersion, growing satisfactorily under different edaphoclimatic conditions and surpassing those of the regions of origin. Less than 1 % of these 600 species have been used for industrial purposes. In essence, the use of eucalyptus in the worldwide industry is based on two species, mainly: E. globulus, E. grandisand their hybrids with E. urophylla, and hybrids between E. salignaand E. camaldulensis, planted in large scale in Brazil. These Eucalyptus trees are used for the production of paper, cellulose, wood, coal, cluster, sawmill, furniture, oils for pharmaceutical industries, honey, windbreak, and in civil construction and ornamentation.

The importance of eucalypt plantation for Brazil can be assessed based on the participation of the forest sector in the economy‘s country. Initially supported by governmental tax incentives for reforestation and later by the National Programs for Steel Industry and Charcoal and for cellulose and paper production. Currently, the estimated area of eucalyptus crops in Brazil is of 4.5 million hectares, occupying 66% of the Brazilian reforested area in 2010 [1].

Eucalyptus was considered a genus practically free of diseases until 1970’s. However, the progress of reforestation areas to warmer and wetter regions, with the planting of more susceptible species and the repeated use of the same area for planting, created favorable conditions to the occurrence of diseases. Among the latter is rust disease caused by Puccinia psidii[2, 3]. Besides the eucalyptus, the pathogen infects other species of Myrtaceae[4]. Severe disease infection may cause deformation and necrosis in the shoot of the host reducing the volumetric growth [5-7].

Eucalyptus rust caused by Puccinia psidiiWinter is currently a very common and severe disease affecting crops of eucalyptus, which is highly susceptible to the disease when it is younger than two years old [8]. Native of South America, rust was first reported in Brazil in 1929 [9] and formally described in 1944 [10]. Nowadays, it is one of the most important diseases of Eucalyptusin the country. It affects both seedlings in the nursery and young plants, up to two years old, in the field, reducing the culture productivity and sometimes leading the most susceptible species to death. It may also infect shoots after clear-cutting and clonal gardens and mini-gardens. The first considerable damages were caused in Espírito Santo in the 1970’s to crops of Eucalyptus grandis, which were less than two years old and imported from South Africa (IPEF). In São Paulo State, the first cases of this disease were found in commercial crops of this same species in the 1990’s. High infection rates were also detected for both nurseries and crops in the regions of Vale do Rio Doce, Minas Gerais, Espírito Santo and South of Bahia.

According to a survey carried out by Furtado & Marino (2003), P. psidiiwas found in 14 eucalyptus species and 23 native and exotic Myrtaceae species in Brazil. Besides eucalyptus, this pathogen infects other species of Myrtaceae such as guava, myrtle, Brazilian grape, strawberry guava, Surinam cherry and jambul trees. In these Myrtaceae hosts, besides meristematic vegetative tissues, the fungus infects flowers and growing fruits and may lead to significant losses [11]. Myrtaceae is considered as Eucalyptus rust’s original host.

Puccinia psidiiis a serious threat to eucalyptus crops in different parts of the world, especially in Australia, to where eucalyptus is native. Occurrences have also been reported in some South American countries such as: Argentina, Colombia, Ecuador, Paraguay, Uruguay and Venezuela; Central America, in the following countries: Cuba, Dominican Republic, Jamaica, Puerto Rico and Trinidad; and North America in South Florida [12]. Puccinia psidiiincidences were also reported in Japan [13] and Hawaii [14], both for the species Metrosideros polymorpha.

There are reports of Puccinia psidiiattacks to plant species endemic to Australia such as Melaleuca quinquinerviain Florida [15] and Acmena smithiiin Brazil [16]. Recently, [17] found Uredo rangelii(morphologically different from P. psidii) parasitizing the species Agonis flexuosa, Callistemon viminalisand Syncarpia glomulifera.

Eucalyptus rust is no longer a disease that causes considerable damages only in rare occasions [11]. During the surveys of Eucalyptusplantations in Mozambique in May and July 2009, typical rust disease symptoms were observed on eucalyptus trees in several localities in Maputo Province, as well as in Niassa Province. Subsequently, the rust disease has also been found in KwaZulu-Natal in South Africa. These were disturbing findings given the importance of eucalyptus or guava rust fungus, Puccinia psidii. Thus far, P. psidiihas been the only known rust fungus associated with Eucalyptusspecies, and it is one of the greatest threats to Eucalyptusforest plantation and to Myrtaceaein natural forest ecosystems. Urediniospores have been found and shown to be distinct from P. psidii[18].

Data related to damage are shown in Table 1. It considers 30 m3/ha/year, seven years for harvesting, 20% of medium damage, and USA 700/ton of pulp. The losses of eucalyptus wood account for more than 2 million dollars per year in Brazil.

## 8. Conclusions

The use of chemical control of eucalyptus rust, in the field, in Brazil is relatively recent. It has grown in importance in the last years since the number of epidemics is increasing, eucalyptus has becoming more like a agronomic crop and less of a forest tree, and due to restriction of genetic basis of breeding programs. Resistance sources have become scarcer and easily overcome by the diversity and the variability of pathogens, including eucalyptus rust. Therefore, chemical control has become a component of great importance in integrated management.

The materials for chemical control have been evolved rapidly, from older products such as cuprous and dithiocarbamates to strobilurins, and recently, the mixture of the latter with triazoles become common approach. This trend has been seen in other pathosystems such as rusts of wheat and soybean. There is still much to be done to find the phenological stage and the selection of areas of higher risk to start control, clonal mosaic composition with different resistance genes to prevent the pathogen proliferation, and rotation of different active principles to increase their lifetime, preventing the emergence of resistant isolates.

The chemical control of eucalyptus rust, as well as its application methods, is viable since it reduces damages and losses to eucalyptus crops. It may also allow the maintenance of clones that are highly productive but susceptible to the disease.

Perspectives in the scenario of integrated handling of plant diseases, within the context of epidemiology point, to studies of disease dynamics, geostatistical and climatic, by mathematical modeling. Fundamentally, additional tools such as using fungicides and genetic improvement, from studies of inheriting resistance and hybridization, are complementary and essential for the success of integrated crop handling.

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© 2013 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Marcus Vinicius Masson, Willian Bucker Moraes and Edson Luiz Furtado (May 15th 2013). Chemical Control of Eucalyptus Rust: Brazilian Experiences, Fungicides - Showcases of Integrated Plant Disease Management from Around the World, Mizuho Nita, IntechOpen, DOI: 10.5772/56319. Available from:

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