DESPITE a lot of research having been done into greyback cane grubs there is still no way of predicting where, when and to what extent crop damage will occur from this destructive cane root eater.
The problem was raised at a BSES shed meeting in 2007, which resulted in the Mt Kinchant Grower Group deciding to investigate, monitor and hopefully gain more information about the life cycle of the grub from, which it was hoped they would gain insights into predicting when and where they could expect infestations.
The Mt Kinchant Grower Group: chairman Paul Vassallo; secretary Andrew Vassallo; and Charles Vassallo; Mark Craig; Joe Muscat; Eddie Pace; John Walker; Fritz Attard; and Julian Vassallo and BSES principal entomologist Dr Peter Samson and research technician Allen Eaton worked on the project, which accessed $80,000 over three years from the Sugar Research and Development Corporation.
Dr Samson said there was no standard method enabling growers to determine the risk of grub attack to a specific place in a cane block and enabling them to target treatments accordingly. So they wanted to develop a system that would help them decide where to treat for canegrubs from year-to-year so they could invest their time and money to achieve the best results possible.
"The Brightly area (30km west of Mackay) had severe infestations of canegrubs in 2004, 2005 and 2006 and we lost about 20 per cent of our crop in each of those years," Paul Vassallo said.
"After harvest we noticed dead areas of cane in different blocks, which indicated the grubs had done the damage but there was no rhyme or reason for it. In some blocks, lines of cane were dead down the row while in others it showed up as large circular areas.
"We had no way of telling how bad the problem was likely to be the next year, so if we were going to treat for grubs we had to cover all our plant and ratoon cane each year, which made it very expensive.
"The group contracted to have an aerial photographic survey carried out on the 1120 hectares involved in the trial but we found it was difficult to tell whether the cane was waterlogged, affected by canegrubs or we were looking at patches of vine.
"The BSES did the technical work of scouting grub numbers and in trying to break the life cycle by interrupting it at an appropriate time but as yet we haven't been able to identify the right time.
"It's my feeling we're creating a 'nursery' for the grubs under the trash blanket. As the beetles lay their eggs under the trash and the baby grubs eat the cane roots, we need to break that cycle at either the mating or hatching stage."
Group secretary Andrew Vassallo said the group now had a better understanding of the problem but more work was needed to identify the beetle's preferred feeding trees.
"We've noticed the adult beetles attack some fig and palm trees and eat almost all the leaves so we need to find out why certain trees attract them.
"But our main focus has to be discovering what attracts the females to the sites they lay their eggs. Is it the wind that blows them to the area or are they returning to the place they were hatched?
"We need to answer these questions before we can develop a really effective predictive strategy."
An unexpected benefit of the trial has been the encouragement it gave growers to discuss the problem and although the funding will run out in June this year, with the final report due soon afterwards, the die is cast and the networking is expected to continue.
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