Weather-based prediction of anthracnose severity using artificial neural network models

Data were collected and analysed from seven field sites in Australia, Brazil and Colombia on weather conditions and the severity of anthracnose disease of the tropical pasture legume Stylosanthes scabra caused by Colletotrichum gloeosporioides. Disease severity and weather data were analysed using artificial neural network (ANN) models developed using data from some or all field sites in Australia and/or South America to predict severity at other sites. Three series of models were developed using different weather summaries. of these, ANN models with weather for the day of disease assessment and the previous 24 h period had the highest prediction success, and models trained on data from all sites within one continent correctly predicted disease severity in the other continent on more than 75% of days; the overall prediction error was 21.9% for the Australian and 22.1% for the South American model. of the six cross-continent ANN models trained on pooled data for five sites from two continents to predict severity for the remaining sixth site, the model developed without data from Planaltina in Brazil was the most accurate, with >85% prediction success, and the model without Carimagua in Colombia was the least accurate, with only 54% success. In common with multiple regression models, moisture-related variables such as rain, leaf surface wetness and variables that influence moisture availability such as radiation and wind on the day of disease severity assessment or the day before assessment were the most important weather variables in all ANN models. A set of weights from the ANN models was used to calculate the overall risk of anthracnose for the various sites. Sites with high and low anthracnose risk are present in both continents, and weather conditions at centres of diversity in Brazil and Colombia do not appear to be more conducive than conditions in Australia to serious anthracnose development.

Postharvest conservation of 'Tommy Atkins' mango fruit influenced by gamma radiation, wax, hot water, and refrigeration

It was aimed to extend the postharvest conservation of 'Tommy Atkins' mango fruits harvested in break maturity stage. Fruits were submitted at the following treatments: hot water treatment (55°C for 5 minutes) and benomyl 1,000 mg.L-1; irradiation with 0,8 or 1,0 kGy; irradiation associated at carnaúba wax; and control. The fruits were stored at 10°C and 85 - 90%RH during 21 days, and then removed to ambient temperature (25,7±0,7°C and 87,1±2,2%RH). Through the storage time, the evolution of fresh weight, color, rottenness, total soluble solids (TSS), total titratable acidity (TTA), and TSS/TTA ratio were measured. 'Tommy Atkins' mango fruits can have shelf life notably increased, when they were submitted to hot water treatment (55°C for 5 minutes) or γ radiation (0,8 and 1,0 kGy), associated with carnaúba wax application, before cold storage. These treatments increased the fruit resistance at refrigerated storage, and improved shelflife after transferring to ambient temperature.

Evaluation of systems for timing of fungicide sprays for control of postbloom fruit drop of citrus in Brazil

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum, infects petals of citrus flowers and produces orange-brown lesions that induce the abscission of young fruitlets and the retention of calyces. Proper timing of fungicide applications is essential for good disease control. Different systems for timing of fungicide applications for control of PFD in a major citrus-growing region in southern São Paulo state in Brazil were evaluated from 1999 to 2002. The following programs were compared to an unsprayed control using counts of diseased flowers, persistent calyces, or fruit: (i) a phenology-based program currently recommended in Brazil with one application at early and another at peak bloom; (ii) the Florida PFD model; (iii) the postbloom fruit drop-fungicide application decision system (PFD-FAD), a new computer-assisted decision method; and (iv) grower's choice. In 1999, no disease developed, sprays applied with the phenology-based program had no effect, and the Florida PFD model saved two sprays compared with the phenology-based program. In 2000, PFD was moderate and the phenology-based and growers' choice treatments had a significantly lower number of persistent calyces and higher fruit numbers than the control, but no differences were found between those treatments and the PFD model. In 2001, PFD was severe with considerable yield loss. The PFD model, the phenology-based program, and the grower's choice reduced flower blight and the number of persistent calyces, and improved fruit yields with two to three applications, but the PFD-FAD achieved comparable yields with only one spray. In 2002, the disease was mild, with no yield loss, and the Florida PFD model and the PFD-FAD saved one spray compared with the other systems. The PFD model and the PFD-FAD were equally effective for timing fungicide applications to control PFD in Brazil. Scouting of trees is simpler with PFD-FAD; therefore, this system is recommended and should eliminate unnecessary sprays and reduce costs for growers.

Endophytic yeasts and filamentous fungi associated with southern Brazilian apple (Malus domestica) orchards subjected to conventional, integrated or organic cultivation

Endophytic fungi were isolated from leaves, flowers and fruit of healthy apple trees (Malus domestica, BORKH.) growing in southern Brazilian orchards under three different cultivation systems (conventional, integrated and organic), during two vegetative cycles. The greatest total number of endophytic isolates was obtained from the orchards under organic cultivation when compared to integrated and conventional cultivation systems. Filamentous fungi from the genera Colletotrichum, Xylaria and Botryosphaeria were the most frequent ones and the most representative yeast genera were Sporobolomyces, Rhodotorula, Debaryomyces and Cryptococcus. It is suggested that some isolates may be used as indicators of the different management systems. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

Conservation and use of palm trees in Brazil's landscaping

Palm trees belong to the Arecaceae family and are widely utilized in landscaping of tropical countries. Although there are many species, just a few are used in Brazil's landscaping, the majority coming from other countries. So, this study had the objective to characterize the plants in the collection of palm trees at UNESP/FCAV, Campus of Jaboticabal, Sao Paulo State, Brazil. The germination of seeds was also studied to increase the production of seedlings for use in landscaping, as this is the biggest difficulty for spreading new species. The introduction of new species in the collection was accomplished. It was also made a survey of major pests and diseases that occur in the collection. The most common pests found were: Brassolis sophorae, Parisoschoenus obesulus, Rhynchophorus palmarum and Coraliomela sp., and the most common disease causing fungi: Colletrotrichum sp., Curvularia sp., Bipolaris sp., Helminthosporium sp., Alternaria sp., Phyllosticta sp., Pestalotia sp., Exosporium palmivorum and Ceratocystis pardoxa.

Postharvest decay development on guava stored under several controlled atmosphere conditions

The control of post-harvest fungal decay on guava (Psidium guajava L. 'Pedro Sato') stored under low oxygen controlled atmosphere (5 kPa) was compared with increasing concentrations of carbon dioxide in the atmospheres. The combination of high concentrations of carbon dioxide (1, 5, 10, 15 and 20 kPa) with low oxygen (5 kPa) did not result in additional decay control. The low oxygen level (5 kPa) was the main factor for controlling post-harvest fungal development which resulted in a very low percentage of fruits with symptoms of anthracnose and stylar end rot throughout cold storage, regardless of the CO2 concentration. After transfer to ambient conditions, only the atmospheres with 5 kPa O2 (control), 5 kPa O2 + 1 kPa CO2 and 5 kPa O2 + 5 kPa CO2 resulted in reduced incidence of stylar end rot (P<0.05). There was not a significant interaction among CA combinations and storage duration on the percentage and number of typical anthracnose lesions.

Controle químico de doenças de Eucalyptus spp. em viveiros e seus efeitos morfo-fisiológicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção de exo-biopolímeros por ascomicetos e seu potencial de utilização na biossorção de cádmio e chumbo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Teste de condutividade elétrica e presença de patógenos em sementes de soja

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Interferência de patógenos nos resultados dos testes de vigor em sementes de feijoeiro

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mapas de zonas de risco de epidemias para doenças dos citros no Estado de São Paulo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização morfométrica, patogênica e genética de isolados de Colletrotrichum gloeosporioides, agente causal da antracnose em manga (Mangifera indica L.)

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Estresse oxidativo em clones de seringueira sob ataque de antracnose-das-folhas

Pós-graduação em Ciência Florestal - FCA

Avaliação de leveduras isoladas de áreas agrícolas como agentes no controle biológico de fitopatógenos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)