During the years of 2004/05 and 2005/06, in Piracicaba, State of São Paulo, experiments were carried out with cotton crop under conventional tillage seeding and no-tillage. The seeding was performed over the mulching of millet, with the objective to evaluate if such mulching could interfere on temperature, leaf wetness duration (LWD) and development of ramulosis in cotton crop. It was also used the Favorability Index for the based on ramulosis cotton crop to explain the development differences of the disease the two seeding systems. Weather variables data were measured by an of acquisition data platform of the experimental area. The disease was measured by scales from 1 to 5 and the average was submitted to a statistic analysis. The difference on ramulosis severity between cotton crop under conventional tillage and conventional seeding was due to specific interactions for each period where many variables were involved (stage of the development of the plant and the macro and microclimatic conditions). The favorability index had a good relation with the increase of the ramulosis severity between both seeding systems. Ramulosis severity can be higher in conventional production system than in systems that uses mulching, particularly in periods when the index values are high: association of rain periods with crop susceptibility to the pathogen. When the index is lower than 0,500 effective increases on ramulosis severity is not observed in any seeding system.
no-tillage; cotton; ramulosis; microclimate
