Prácticas culturales para el manejo de la Sigatoka negra en bananos y plátanos

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.

Respostas fisiológicas em mudas de banananeira tratadas com estrobilurinas

There are reports that strobilurin besides having a fungicide effect can promote physiologic benefits to the plants. However, this effect on banana plants was not studied yet. The objective of the present study was to evaluate the effect of strobirulins on the physiology of banana plantlets. For this purpose, cultivar Grand Naine banana plantlets were transferred to pots containing substrate and kept in a nursery with 50% shading. The experimental design was a completely randomized design with three treatments (water, azoxystrobin and pyraclostrobin) and five replications. The treatments were applied at 15, 30, 45, 60 and 75 days after transplanting at a dose 100 g a. i. ha(-1) with manual spray. Plant height, pseudostem diameter, shoot dry matter in strobilurin treated plants were higher than the untreated plants, however, the effect of fungicide treatment was different, being the most pronounced effect of pyraclostrobin compared to azoxystrobin. Plants treated with pyraclostrobin had higher leaf area, nitrate reductase activity and chlorophyll content of leaf total nitrogen than the plants treated with azoxystrobin and water, which did not differ. Strobilurins affect the physiology of the banana plantlets differently, the effect being more pronounced by pyraclostrobin.