Emília Hamada

Climate change and plant diseases

As atividades antropicas estao alterando as concentracoes de gases de efeito estufa da atmosfera e causando mudancas no clima do planeta. Certamente, num futuro proximo, devido as mudancas climaticas globais, ocorrerao modificacoes no cenario fitossanitario brasileiro. Os impactos podem ser positivos, negativos ou neutros, pois as mudancas podem diminuir, aumentar ou nao ter efeito sobre as doencas, em cada regiao ou epoca. Esses impactos tambem serao observados sobre as plantas e outros organismos, alem de outros componentes do agroecossistema. Porem, esses impactos nao sao facilmente determinados e, desta forma, os especialistas das diferentes areas precisam ir alem de suas disciplinas e abordar os impactos das mudancas climaticas em um contexto mais amplo. Nessa revisao sao discutidos os aspectos relacionados com os efeitos das mudancas climaticas sobre as doencas de plantas. Na distribuicao geografica e temporal das doencas, um contexto historico e apresentado, incluindo estudos recentes utilizando dados de modelos de previsao do clima futuro associados com modelos de simulacao da doenca a fim de predizer a distribuicao nos cenarios climaticos futuros. Tambem sao apresentados os cenarios futuros de previsao de doencas de algumas culturas no Brasil. Sobre os efeitos do aumento da concentracao de CO2 atmosferico e outros gases sao discutidos importantes aspectos do comportamento das doencas sujeitas as condicoes alteradas de gases atmosfericos no futuro. As consequencias dessas alteracoes sobre o controle quimico e biologico das doencas de plantas tambem sao discutidas.

Risk analysis of climate change on coffee nematodes and leaf miner in Brazil

The objective of this work was to assess the potential impact of climate change on the spatial distribution of coffee nematodes (races of Meloidogyne incognita) and leaf miner (Leucoptera coffeella), using a Geographic Information System. Assessment of the impacts of climate change on pest infestations and disease epidemics in crops is needed as a basis for revising management practices to minimize crop losses as climatic conditions shift. Future scenarios focused on the decades of the 2020s, 2050s, and 2080s (scenarios A2 and B2) were obtained from five General Circulation Models available on Data Distribution Centre from Intergovernmental Panel on Climate Change. Geographic distribution maps were prepared using models to predict the number of generations of the nematodes and leaf miner. Maps obtained in scenario A2 allowed prediction of an increased infestation of the nematode and of the pest, due to greater number of generations per month, than occurred under the climatological normal from 1961-1990. The number of generations also increased in the B2 scenario, but was lower than in the A2 scenario for both organisms.

Análise de risco das mudanças climáticas globais sobre a sigatoka-negra da bananeira no Brasil

O conhecimento dos provaveis impactos das mudancas climaticas globais sobre a ocorrencia de doencas de plantas e de grande importância para o setor agricola, pois permite a elaboracao de estrategias de controle. O presente trabalho teve por finalidade estudar os possiveis impactos das mudancas climaticas sobre a sigatoka-negra da bananeira, por meio da elaboracao de mapas de distribuicao da doenca confeccionados a partir dos cenarios disponibilizados pelo IPCC. Os mapas mostraram que havera reducao da area favoravel a doenca no pais. Tal reducao sera gradativa para as decadas de 2020, 2050 e 2080 e de forma mais acentuada no cenario A2 que no B2. Apesar disso, extensas areas ainda continuarao favoraveis a ocorrencia da doenca, especialmente no periodo de novembro a abril.

Incubation period of Hemileia vastatrix in coffee plants in Brazil simulated under climate change

Risk analysis of climate change on plant diseases has great importance for agriculture since it allows the evaluation of management strategies to minimize future damages. This work aimed to simulate future scenarios of coffee rust (Hemileia vastatrix) epidemics by elaborating geographic distribution maps using a model that estimates the pathogen incubation period and the output from three General Circulation Models (CSIRO-Mk3.0, INM-CM3.0, and MIROC3.2.medres). The climatological normal from 1961-1990 was compared with that of the decades 2020s, 2050s and 2080s using scenarios A2 and B1 from the IPCC. Maps were prepared with a spatial resolution of 0.5 × 0.5 degrees of latitude and longitude for ten producing states in Brazil. The climate variables used were maximum and minimum monthly temperatures. The maps obtained in scenario A2 showed a tendency towards a reduction in the incubation period when future scenarios are compared with the climatological normal from 1961-1990. A reduction in the period was also observed in scenario B1, although smaller than that in scenario A2.

Research approaches, adaptation strategies, and knowledge gaps concerning the impacts of climate change on plant diseases

This review discusses the present trends in studies on the impacts of climate change on plant diseases. Firstly, the approaches used for studying the potential effects of altered temperature, water availability, CO2 and O3 air concentrations, and UV-B radiation on components of the disease cycle are explained and discussed. Next, the impact of changes in climate patterns on the geographic and temporal distribution of diseases by integrating biological and epidemiological models into geographic and climate databases are assessed. Finally, adaptation strategies are discussed and areas where there is a recognized lack of knowledge are highlighted. The literature shows that different pathosystems respond in different ways to climate change. Thus, case-by-case studies on the responses of crop species or varieties and their diseases to climate change are necessary. In addition to that, wide-scale projections of disease risk are necessary in order to identify research priorities, whereas industry must be strategically directed and public policies developed to establish adaptation measures and to prevent potential food security crisis. Only by conducting long-term and multidisciplinary studies can we reduce the uncertainty regarding the effects of climate change on plant diseases.

Climatic risk of grape downy mildew (Plasmopara viticola) for the State of São Paulo, Brazil

Viticulture in Brazil has been growing in importance in recent years. In the State of Sao Paulo, a significant percentage of the production is basically destined to in natura consumption and, more recently, much effort has been made by institutions to revitalize the viticulture in the State. Among fungal diseases, the downy mildew (Plasmopara viticola) is one of the main diseases affecting this crop in Brazil, with extreme damage effects on its production. The objective of this study was to estimate the incidence of the downy mildew on grape under the climatic conditions of the State of Sao Paulo, based on a mathematical model and using Geographical Information System - GIS tools. The study considered the months from September to April, a period in which the downy mildew can affect grapevines under development. Mean temperature and relative humidity were the basic weather data entered in the GIS database. Leaf wetness duration was estimated from relative humidity measurements. Climatic data entered in the GIS were used to calculate and produce maps depicting the severity of the grape downy mildew, through the application of a disease model. Three cities were evaluated (Jales, Jundiai, and Sao Miguel Arcanjo), since they represent the main vineyard centers in the State. The adopted methodology permitted quantifying the severity of the grape downy mildew not only in spatial terms, identifying the variability among the different regions of the State, but also in temporal terms, along the months, making an adequate distinction of the studied cities.

SPATIAL AND TEMPORAL VARIABILITY OF LEAF WETNESS DURATION IN THE STATE OF SÃO PAULO, BRAZIL

One of the main factors influencing the occurrence of plant diseases is the leaf wetness duration (LWD). However, this climatic parameter is not generally and systematically recorded at meteorological stations, and the alternative to obtain an estimate for LWD is the use of mathematical models. The objective of this study was to estimate LWD for the State of Sao Paulo, on the basis of the number of hours with relative humidity equal to or higher than 90%, and also plot them on a map with help of the Geographical Information System (GIS) tool. Using daily relative humidity data from ten meteorological stations of the State, for six years, adjustment equations were obtained for different LWD periods (hours day-1) (R2 from 0.58 to 0.81) and of number of days (ND) per month with LWD for a period equal to or higher than ten consecutive hours (R2 from 0.57 to 0.75), both as functions of the mean relative humidity. The mean LWD and the mean ND varied among the different regions of the State and different periods of the year. The smallest estimated values of mean annual LWD and ND were observed for the west region of the State, and the highest values for the coastal region.