Black sigatoka (Mycosphaerella fijiensis) control consists in the continuous use of fungicide sprays and cultural practices. Cultural control reduces inoculum sources of the pathogen and favorable environmental conditions for its development, as well as it increases the vigor of the plants. In order to manage the disease it is necessary to know its behavior through the time, its relationship with the weather and the crop management. The most important cultural practice to reduce the inoculum source is the removal of the whole affected leaves or only the diseased portions of the leaves. The removed tissue is placed over the ground and the use of urea is feasible to accelerate its decomposition. An alternative practice is the "mini-composting" that consists in forming small heaps with the dead leaves and harvested plants for its quick degradation, which allows to reduce the pathogen inoculum and to incorporate nutrients and organic matters into the soil. The early pruning of the tips of the Young leaves before they show symptoms of the disease and the quick elimination of harvested plants reduce the inoculum. Also, the agronomic management of the crop helps to reduce the favorable conditions and to increase the vigor of the plants: this management considers plantation density, drainage systems, irrigation methods, control of weeds, chemical-biological fertilization, and nematode control.El control de la Sigatoka negra (Mycosphaerella fijiensis) se basa en el uso continuo de fungicidas y prácticas de cultivo. El control cultural reduce las fuentes de inóculo del patógeno y las condiciones favorables para su desarrollo, así como incrementa el vigor de las plantas. Para combatir la enfermedad se requiere conocer su comportamiento a través del tiempo, su relación con el clima y las prácticas de manejo. La práctica más importante para reducir la fuente de inóculo es la remoción de hojas afectadas o porciones de éstas. El tejido removido se deposita en el suelo y es factible la aplicación de urea para acelerar su descomposición. Una práctica alternativa es el "minicomposteo", que consiste en colocar la hojarasca y plantas cosechadas en pequeños montones para su rápida degradación, lo cual reduce el inóculo e incorpora nutrientes y materia orgánica al suelo. La poda temprana de las puntas de hojas jóvenes (antes de presentar lesiones esporuladas) y la eliminación rápida de plantas cosechadas disminuyen el inóculo. También, el manejo agronómico del cultivo como densidad de plantación, sistemas de drenaje, métodos de riego, control de malezas, fertilización química-biológica y control de nematodos, ayuda a reducir las condiciones favorables para el desarrollo de Sigatoka negra e incrementar el vigor de las plantas

The chemical management of the black leaf streak disease in banana caused by Mycosphaerella fijiensis (Morelet) requires numerous applications of fungicides per year. However this has led to fungicide resistance in the field. The present study evaluated the activities of six fungicides against the mycelial growth by determination of EC50 values of strains collected from fields with different fungicide management programs: Rustic management (RM) without applications and Intensive management (IM) more than 25 fungicide application/year. Results showed a decreased sensitivity to all fungicides in isolates collected from IM. Means of EC50 values in mg L-1 for RM and IM were: 13.25 ± 18.24 and 51.58 ± 46.14 for azoxystrobin, 81.40 ± 56.50 and 1.8575 ± 2.11 for carbendazim, 1.225 ± 0.945 and 10.01 ± 8.55 for propiconazole, 220 ± 67.66 vs. 368 ± 62.76 for vinclozolin, 9.862 ± 3.24 and 54.5 ± 21.08 for fludioxonil, 49.2125 ± 34.11 and 112.25 ± 51.20 for mancozeb. A molecular analysis for β-tubulin revealed a mutation at codon 198 in these strains having an EC50 greater than 10 mg L-1 for carbendazim. Our data indicate a consistency between fungicide resistance and intensive chemical management in banana fields, however indicative values for resistance were also found in strains collected from rustic fields, suggesting that proximity among fields may be causing a fungus interchange, where rustic fields are breeding grounds for development of resistant strains. Urgent actions are required in order to avoid fungicide resistance in Mexican populations of M. fijiensis due to fungicide management practices.

Resumen. El psílido asiático de los cítricos (PAC; Diaphorina citri) es la plaga más importante que afecta a la lima mexicanao (Citrus aurantifolia) en el trópico seco de México y es el vector de la enfermedad del Huanglongbing. Su control se basa en el uso de insecticidas sintéticos. La búsqueda de alternativas sustentables y eficaces es una prioridad en el manejo del PAC. En este estudio, se evaluó el efecto de diferentes tipos de aceites y extractos de plantas en el control de ninfas del PAC en el estado de Colima, México. Las pruebas fueron conducidas en árboles de lima mexicana y plantas de vivero infestadas con la plaga. Se realizó una aplicación foliar de cada tratamiento sobre brotes vegetativos de 5 a 7 días de edad. Las evaluaciones del número de ninfas vivas se hicieron antes y después de la aplicación de los aceites y los extractos de plantas. En la primera prueba, el aceite parafínico (99% de residuos no sulfonados) a concentraciones de 1, 2, y 3%, redujeron la población del PAC entre un 77 a... The Asian citrus psyllid (ACP; Diaphorina citri) is the most important pest affecting Mexican lime (Citrus aurantifolia) in the dry tropics of Mexico, and is the vector of huanglongbing disease. Its control is based on synthetic insecticides. The search for sustainable and effective alternatives is a priority in the management of ACP. In this study, the effect of different kinds of oils and plant extracts were evaluated to control ACP nymphs in Colima, Mexico. The tests were conducted on mature Mexican lime trees and nursery plants infested with the pest. One foliar application of each treatment was done to tagged 5-7 d shoots. Paraffinic oil (99% of unsulfonated residues) at 1, 2, and 3%, reduced the ACP population between 77 to 98% as compared with the untreated control. Different paraffinic oils, cooking oils, and citrus oil maintained a low infestation of ACP compared to the control. Also, neem, garlic, and onion extracts showed a significant reduction of ACP nymphs. Jatropha curcas seed oil...

A multiplex-PCR method was developed to identify the distribution and frequency of the mating types of the fungal banana leaf pathogen Mycosphaerella fijiensis in Mexico. PCR amplification identified different sized fragments for mat1-1 and mat1-2 genes. The same primers were also used to amplify fragments of the idiomorphs of Mycosphaerella musicola, another important banana pathogen closely-related to M. fijiensis. These were sequenced and were highly similar to M. fijiensis. Single conidial isolates of M. fijiensis were obtained from different fields in regions of Mexico not previously sampled, and from different banana and plantain cultivars, to determine the frequency and distribution of the mating types within natural populations. The multiplex primers and methods used for population analysis in M. fijiensis could also be applied to M. musicola populations andmay also be applicable to determine mating types in other closely related species, for a better understanding of the Mycosphaerella complex of pathogens and saprophytes associated with banana leaves. Additional keywords: epidemiology, fungal hybridisation, genetic mapping, virulence.