J. E. Cardoso

Diseases of cashew nut plants (Anacardium occidentale L.) in Brazil

Abstract Cashew is an extremely important source of income for thousands of people in the Brazilian Northeastern—in growing the plant, in harvesting the nuts, in processing the kernels and apples, and in marketing the products. Diseases have been reported to cause significant cashew yield loss in Brazil, a major cashew-producing country. Anthracnose is by far the most important disease. Other foliar infections, namely black mould, angular leaf spot and powdery mildew are considered of lesser importance. Gummosis of branches and trunk has increased its severity in all northeastern producing states. Nematode attack has so far not been detected in this crop. Fungal deterioration of kernels, a pre- and post-harvest problem, causes losses of million of dollars per annum. The spraying of pesticides in Brazilian cashew plantatations is seldom practiced by most farmers due to economic and social reasons. Some diseases are more severe on dwarf cashew clones than on common tall cashew plants.

First report of black branch dieback of cashew caused by Lasiodiplodia theobromae in Brazil.

Cashew nut (Anacardium occidentale) is one of the most important cash crops of northeastern Brazil. A new disease, named here as black branch dieback, caused by Lasiodiplodia theobromae, was observed causing serious damage on as many as 30% of the trees in some orchards in both coastal and inland semiarid cashew-growing areas of Ceará and Piauí states of Brazil, respectively. The disease symptoms are first observed as darkened, elongated lesions on stems near the branch apexes of herbaceous tissues. Gum exudation is common from lesions, which expand rapidly to affect the entire branch, leading to branch death. Diseased plants were collected, and L. theobromae was consistently isolated from canker tissues. Fresh mycelial disks of the fungus were used for artificial inoculation of healthy plants. Shoots of young cashew plants were inoculated on the apex by inserting a 3-mm plug taken from actively growing colonies on potato dextrose agar into an incision made with a sterile scalpel. Agar plugs with no mycelium were placed into incised plant shoots to serve as controls. Plants were incubated in a greenhouse at 28°C. Symptoms developed within 15 days after inoculation. Artificially inoculated plants showed symptoms similar to those that were naturally infected. L. theobromae was consistently reisolated from inoculated plants. The disease seems to occur throughout the year, but it spreads faster during the rainy season. A contagious disease pattern within the orchard was observed with a decreasing gradient from the orchard perimeter to the interior of the field, suggesting an external source of primary inoculum. All improved dwarf cashew clones were susceptible, but the newly released clone END-189 was the most susceptible. Black branch dieback may reduce tree growth, nut yield, and eventually cause plant death. Plant susceptibility is not related to its age however; only herbaceous tissues are vulnerable to natural infection. A similar disease on floral shoots of cashew caused by L. theobromae was reported by Olunloyo and Esuruoso in Nigeria (1). To our knowledge, this is the first report of L. theobromae causing branch dieback in cashew orchards in Brazil. Reference: (1) O. A. Olunloyo and O. F. Esuruoso. Plant Dis. 59:176, 1975.

First Report of Erysiphe quercicola Causing Powdery Mildew on Cashew in Brazil

Cashewnut (Anacardium occidentale L.) is a very important crop plant native to northern Brazil. In 2010 and following years, a powdery mildew outbreak was observed in over 60% of cashew growing areas in coastal and highland fields in Ceará and Piauí states, which account for over 70% of Brazilian cashewnut production. Disease symptoms commonly appeared as white to gray powder on young shoots, inflorescences, young fruits, and leaves, reducing fruit onset and severely damaging apple and kernels. Highest level of infection was observed by the time of flowering and fruiting plant stages, which occurs from June to September in those particular states. Today, powdery mildew is the main pathological constraint of cashew production in Brazil, as it affects mature trees, nursery stocks, and new plantings. Although there is great variability within cashew genotypes, most growing varieties are susceptible. From 2012 until 2014, field surveys were conducted to collect samples from different environments and host genotypes. Severely infected flushing leaves of BRS 189 cashew clone were collected in Pacajus county, Ceará State, and introduced into the Laboratory of Plant Pathology, Embrapa, for further studies. Due to conspicuous differences between these and commonly known symptoms from early described powdery mildew (Noack 1898), morphological and sequence data molecular studies were then conducted in order to determine the causal fungus. Conidiophores were erect with cylindrical foot cells, average size 100.2 μm. Chasmothecia were absent. Primary conidia were ellipsoid, with a rounded apex and truncate base. Mature conidia were mainly dolioform and formed singly (no catenescent), measuring 26.9 to 31.7 μm long × 14.3 to 20.4 μm wide (avg. 29.9 × 14.8 μm), with length/width ratio of 1.8 on average. The internal transcribed spacer (ITS) region, including 5.8S and partial 28S from genomic DNA extracted, was amplified with ITS1F (5′-TCCGTAGGTGAACCTGCGG-3′) and P3 (5′-GCCGCTTCACTCGCCGTTAC-3′) primers. The amplicon was sequenced by external service (Macrogen, Seoul, South Korea). BLASTn analysis of the ITS sequence (661 pb) Quick Links

Análise do progresso e danos causadas pelo amarelão do meloeiro

The analysis of progress and the yield losses due to melon yellowing, caused by Melon yellowing-associated virus (MYaV), were studied in two melon hybrids (Aclain and Frevo) under natural infection in a commercial field in Russas county, Ceara State (Brazil). Plants were monitored throughout a growing cycle following the incidence of melon yellowing. By the end of the cycle, fruits were harvested, weighted and sampled to estimate the total solid soluble (TSS). The linear, exponential, monomolecular, logistic and Gompertz models were used for examining their suitability in fitting growth data. The monomolecular model attained the best fitness to describe the data for both hybrids according to the coefficient of determination and error mean square, although the Gompertz model also described the data well for the Aclain hybrid. Fruit weight and TSS contents were not affected by melon yellowing in both hybrids.

First report of Robillarda sessilis associated with Anacardium occidentale and Beaucarnea recurvata leaf spots in Brazil.

Laboratório de Fitopatologia, Embrapa Agroindústria Tropical, 60511-110, Fortaleza-Brasil; Departamento de Fitotecnia, Universidade Federal do Ceará, 60021-970, Fortaleza-Brasil; Departamento de Agronomia, Universidade Federal Rural de Pernambuco, 52171-900, Recife-Brasil. Autor para correspondência: Francisco das Chagas Oliveira Freire (francisco.o.freire@embrapa.br) Data de chegada: 11/08/2016. Aceito para publicação em: 14/02/2017. 10.1590/0100-5405/167248