Growers are reminded that now is a good time to soil sample but not only for nutrition for next year’s crop but also to see what levels of Pachymetra exist on blocks that are going into fallow.
Pachymetra Root Rot is a root disease caused by a fungus which can impact all areas of the sugar industry value chain. The disease attacks the sugar cane root system, causing yield and stool loss, often accompanied by an increased level of soil going to the mill.
It was first identified in the wet tropics in the 1980s (Magarey 1989) and its impact can be a limiting factor to both productivity and cane quality. Management includes monitoring the level of Pachymetra through soil sampling and where possible planting a high yielding resistant variety. Research by SRA, much of it done locally has determined the critical levels of Pachymetra spores/kg of soil at which crop yield loss can occur. Generally the critical levels start at 50 000 spores/kg for standing crops. It is worth pointing out though that Pachymetra is not a stand-alone issue and management of it needs to be considered along with the many other factors affecting yield and cane quality.
Surveys to monitor this disease were carried out in Tully in 2004 and 2007 by SRA (BSES) and then in 2013 and 2018 by Tully Sugar Limited working with the local SRA lab. These surveys are designed to highlight the issue and remind growers of the need to soil test before planting.
Through these surveys we saw a lift in the levels of Pachymetra in Tully by 2013, which more than likely followed the changeover in varieties once smut hit the industry in 2007. Many of the smut susceptible various were Pachymetra resistant, so we had to move to a range of varieties that could handle smut but were only intermediate for Pachymetra, like Q208 and Q200. Over a period of time the levels of Pachymetra start to increase slowly in for intermediate varieties, Plus the very wet years around 2010-11 could have played a role in helping the disease increase in spores/kg in some sub districts and possibly other regions as well.
In the 2018 survey we saw a good drop in the levels in each of the Tully sub districts, following some drier years plus the introduction of some better yielding Pachymetra resistant varieties like Q253, and Q251. We now have an increasing number of higher yielding Pachymetra resistant varieties that are showing yield promise like SRA 6 and SRA 26 and these should help keep the levels of Pachymetra down to a manageable level in the years ahead.
So Pachymetra is something to consider when going into fallow to help decision making for planting in 2021 and now is a good time to sample, especially with the local TCPSL 2 for 1 deal is still in place. Take one sample, get one free.