15 August, 2003
___CSIRO plant breeder, Dr Greg Constable, is confident that the introduction of Bollgard® II cotton varieties in the 2003-04 transition year will continue to reduce the volume of Heliothis sprays._
Speaking on the weekly Web on Wednesday video (6/8/03) on the CSD website, Dr Constable said the extra gene exhibits much greater efficacy against Heliothis than the current INGARD® gene.
“I think the best rule of thumb that I can use for the time being…is that we have halved Heliothis sprays between conventional and INGARD®, and I would say that we would halve them again with Bollgard® II.
“There have been plenty of Bollgard® II crops in the last two years (relatively low pressure years) that have not required a Heliothis spray, and that’s a good thing, but I think that under heavy pressure there will be a need for one or two maybe,” Dr Constable said.
In relation to mirids, he said growers should start out managing mirids using the same practices applied in managing mirids in INGARD® crops. He said the key to mirid management was to monitor target dates for the appearance of squares or bolls.
A low number of squares would indicate a problem with mirids that would have to be dealt with, while a greater number of squares than thresholds for that time of year would indicate the reverse.
Dr Constable said agronomic issues such as fertilizer and water could also be responsible for squaring nodes falling below target levels.
He said it was important to address fertilizer issues earlier rather than later, and water issues could be addressed on an irrigation cycle basis.
He said fallowed fields were more likely to be healthier and able to provide adequate nutrients, hence Bollgard® II varieties could be ideal in these fields.
“It depends on diagnosing why you are behind. If you are behind because of an insect issue then you address that. If you are behind because the crop is growing slowly, there might be agronomic treatments that you would apply to try and encourage the crop to grow a bit faster.
“You would want to make sure that you had medium size internodes so that the crop wasn’t going to cut out too quickly, and then make sure that you kept up with the target rate of production of those nodes, target rate of production of new fruiting branches, target rate of nodes above white flower, and particularly target boll numbers.”
Dr Constable said he expected Bollgard® II crops to be planted later in areas such as Narrabri, Moree and Goondiwindi because of warmer evenings and the taller growth of plants.
“That tends to minimise the likelihood of early cutout and premature senescence, because vegetative boll load balance is a bit better,” Dr Constable said.
Further Information: *Robert Eveleigh**, John Marshall, Greg Kauter or Craig McDonald
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