Answers to common grower questionsAnswers to common grower questions
It has been difficult to assign yield losses solely to YCS except in cases where blocks were severely affected and where repeated waves of yellowing were observed over an extended period of time.
In these blocks yield reductions of between 30-70 per cent were measured. It should be noted that these severely impacted fields represented a very small percentage of the fields that expressed symptoms. Based upon our data, in less impacted fields (the vast majority) yield losses of 0-15 per cent were more typical.
Although CCS levels appeared to be lower in severely affected cane early in the 2013 crush, the levels improved as the crush continued. Little if any apparent losses of CCS were recorded as the season progressed.
Some growers have reported that fields affected last year are not yet showing YCS symptoms, while others report that YCS is present again.
YCS can impact cane in a number of ways. This can range from yellowing in one or two leaves to yellowing right through the canopy. Depending on the degree of symptoms, crop growth can be compromised with potential impacts on final yields. YCS symptoms may ‘come and go’ in waves through the season.
If you notice yellowing in your crops ensure that you check the symptoms with your local productivity services group. They will help confirm that you have YCS.
Until we identify the cause of YCS, we cannot advise about on-farm management strategies to treat it. However, as part of our research program we are investigating a number of management strategies to see how they impact on YCS. Therefore, we recommend that crops are well managed with optimised inputs.
It has been suggested that YCS may be transmitted in planting material. Although our current trials that look to answer this question are still in progress, we have noticed that when growth conditions are ideal, no yellowing has occurred.
We therefore encourage growers to use approved seed cane where possible and to adopt good farming practices.
YCS has been seen at all stages of plant growth and in all crop classes.
From our observations and those provided by growers in affected regions we believe that stress plays an important role in the expression of YCS.
The two conditions are similar and have similar symptoms. As there is no definite test for Golden Leaf Syndrome (GLS) and we have not yet identified what YCS is, we cannot say that they are the same condition. Nor can we say that YCS has come from Papua New Guinea. More detailed observations of GLS in PNG will be made to see if further insights can be gained, that add to our knowledge of YCS.
Yellow Leaf Syndrome is widespread in Louisiana and other cane-growing states in the United States of America. Similar symptoms to YCS have not been reported in the USA to date.