30 December, 2009
A comprehensive disease survey of the current Australian cotton crop has revealed the cool dry planting conditions severely impacted plant establishment but subsequent warm weather has reduced some diseases.
Speaking on CSD’s Web on Wednesday broadcast, CSD senior plant pathologist Dr Stephen Allen said plant stand establishment – the amount of planted seeds that become plants – was generally well below average courtesy of the tough start.
“A lot of people experienced the warm conditions early in the season, in early September, and they pre-watered and when it came time to plant it was too cold so they delayed planting and when it eventually did warm up the moisture wasn’t there and they had to flush again and use valuable water,” he said.
“So in all areas we found problems with crop establishment – in some cases the seedbed had just dried out too much and the seed was sitting there as good as the day it was in the bag,” he said.
“Emerald had 23 percent seedling mortality this year compared to only 17 percent last year so it’s up a bit. Theodore had 32 percent mortality down from 40 percent the year before but most of the problems then were environmental problems,” he said.
“St George and the Darling Downs were up on seedling mortality problems this year, particularly the Downs where it was only 15 to16 percent mortality last year and it was over 30 percent this year.”
He said stand establishment problems were most severe in fields where cotton was following soybean last season.
Dr Allen also commented on the NSW disease survey reports from Chris Anderson and Peter Lonergan from Industry and Investment NSW.
“All of the areas in New South Wales were generally over 30 percent with the exception of the Bourke and Walgett areas which were about 26 percent mortality and the Macquarie and Murrumbidgee which were about 40 percent.
Dr Allen said while the prolonged dry conditions caused problems with crop establishment, they had resulted in fewer cases of some other problems, including Fusarium Wilt.
“The ideal conditions for Fusarium Wilt are cool, wet springs – which is not exactly what we’ve had this year,” he said.
“In the Queensland survey we found plants with symptoms showing up already in the Darling Downs and St George areas, despite the fact that it’s been fairly dry and warm,” he said.
Dr Allen said while Black Root Rot was common this season, the infestations were not severe and the disease disappeared as the weather warmed up in November.
“Generally the average severity for the disease in NSW was less than one percent – so basically you’re talking about just a small area of the roots being affected so while its causing concern in the fact that it’s there, in terms of severity it’s not an issue,” he said.
“Once the weather warms up, the disease tissue on the outside of the roots falls off and disappears and the plant powers away,” he said.
The cotton industry diseases surveys are a collaboration between Queensland’s Department of Employment, Economic Development and Innovation (DEEDI), Industry and Investment NSW and Cotton Seed Distributors.
Dr Allen said the surveys in New South Wales have been operating since 1983 and in Queensland since the late 1990s. Each year it includes the detailed assessment of up to 130 cotton crops across the country.
He said they provide a good indication on the spread of common diseases, help identify new problems and benchmark the effectiveness of the disease management strategies growers are using.
The surveys will conclude with a return visit to the crops at the end of the season.
“Basically at that stage we look for wilts, boll rots and spots and things but if it stays hot and dry we’re not going to expect to see too many of those…time will tell,” he said.
30 December 2009
Dr Stephen Allen 0267 991500
Above: Dr Steve Allen
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