Macquarie warned that the much-watched Unica forecast for cane output in Brazil's key Centre South region may be too high as forecasts showed a continuation of the rains which causing mounting harvest hiccups.
Brazil's cane crushing pace for 2013-14 "has peaked", Macquarie said, restating an estimate for a 575m-tonne cane crush in Brazil's Centre South region, responsible for some 90% of the country's production.
While still well above last season's 532.6m-tonne harvest, the figure is below an estimate from Unica, the Brazilian cane industry group, of 587m tonnes.
"Rains may have improved cane yields," which have risen some 10% year on year, "but they have disrupted cane harvesting and crushing, with some nine days lost in September alone," Macquarie analyst Kona Haque said.
"Importantly, it has also had a negative impact of diluting the levels of sugars in cane which, at 133 kilogrammes per tonne of cane, is the lowest level in several years."
And there appears little hope of improvement, with "widespread rain" forecast for Brazil's main sugar cane areas over the next two weeks, and with November expected to be wetter than average too
Besides "further reducing sucrose yields this year" the rains "will slow the final leg of the 2013 cane crush", the bank said, pegging Centre South sugar output this season at 32.7m tonnes, a fall of 4.4% year on year.
The comments came as Unica unveiled data for the first half of this month showing a slump of 31% in Centre South sugar production, compared with the first half of October 2012.
The decline reflected rains which, in Piracicaba, reached 62.6mm during the period, twice as much fell during the whole of September, which itself ended on a wet note.
The amount of cane harvested fell 18.0% year on year to 31.2m tonnes, with the impact on sugar output compounded by the low level of sugars in cane, the so-called ATR figure, and by mills' preference for making ethanol rather than the sweetener.
The proportion of cane turned into sugar eased to 46.7% from 46.9% in the second half of September.
Antonio de Padua Rodrigues, the Unica technical director, highlighted that the slowdown meant that "more than 100m tonnes of cane must still be processed by the end of the harvest" to meet the association's forecast.
While 2013-14 is, in terms of time, only a little over half way through, crushing volumes typically collapse sharply into the end of the calendar year, with little processing usually undertaken between December and March, a reflection of the onset of the rainy season.
Cane not harvest by the December or so is typically left standing to be processed early in the next season.