The inhabitants of the Australian north-east coast are probably in a hurry to forget last summer. First, persistent very heavy rainfall put huge tracts of land under water. And then in February, cyclone Yasi, a weather event as big as Hurricane Katrina, swept over the north-east coast, with wind speeds of nearly 300 kilometers an hour.
These weather systems left serious effects on the farms along the coastal strip and also in the inland northern cropping regions. Many cotton farms were flooded, and much of the tropical banana producing area in the north of the state of Queensland suffered very severe damage from the extreme winds. Many of the 4,000 Australian sugar cane growers also suffered. Almost the whole Australian sugar cane cultivation area of 450,000 hectares lies along the very stretches of the eastern and northeastern coast that received the worst battering. Almost all of the sugar cane production in Australia comes from the coastal strip in Queensland between the southern border near the Gold Coast and far North Queensland, a distance of several thousand kilometres. The vast fields of metershigh sugar cane and the many small towns with sugar mills are an iconic image of Queensland’s agriculture. The Australians harvest about 30 million tons of sugar cane each year – producing about five million tonnes of raw sugar, eighty percent of which is exported, mainly to East Asia.
Last season, it will probably have been much less. Estimates by a representative canegrower organisation of the combined damage from the unusually wet weather prior to the arrival of Yasi and the direct effects of Yasi itself indicate that the sugar cane farmers may have lost 500 million Australian dollars (€350 million) or more, which corresponds to about a quarter of the industry’s normal annual turnover: a huge loss.
To make matters worse, Australian sugar cane farmers aren’t just confronted with the vagaries of the weather: like virtually all crops, sugarcane has its own list of pests that have to be dealt with. One of the most feared in Australia is the cane beetle. Farmers are confronted with about 20 different species of this pest.
A particularly damaging one is the greyback cane grub. Graham Blackburn is a farmer who knows the effect of this species only too well. “In the last ten years we have been getting very poor sugar content in the cane”, he says “and we are paid on sugar content.” “Eventually, we could trace this back to the greyback grub.” But this took some time. “At first, we had only noticed that the cane was always sort of unwell, a little bit under stress, but we did not know what the problem was until we had a look at the roots of the plants.” It turned out that, between February and April, the stool (the root system under the clumps of cane) is being attacked so heavily that the plants have hardly any roots left to feed with. It turned out that this was a result of greyback grub.
“It’s mainly the larvae that are the problem,” explains Pat English, who works as a Technical Advisor for Bayer CropScience in Queensland, and has his office in the small town of Mackay – right in the heart of sugar cane country and not far away from the place where Blackburn runs his 800 ha cane and cattle farm. English and his colleagues are all too familiar with the farmers’ problems. “The adult beetles really don’t do any crop damage; they feed on mainly tree leaves for about 2-3 days only when they are about to mate. When they lay their eggs it is most often in sugar cane crops, and when those eggs hatch, the larvae feed on the sugar cane roots. This is where the real damage occurs.” he explains. “Sometimes the root system is damaged so badly that the plant loses its hold in the soil and falls over.”
Risk of cane grub damage
For farmers, this means not only crop losses, but also a lot of extra work and expense to restore the fields to production. The fallen plants have to be removed and replaced with new plantings. This is especially costly because sugar cane is grown using ratoon agronomy, in which farmers do not normally replant every year, but instead practice so-called ratooning, which simply involves letting the stubble that remains after harvest stand in the field. The stalks then reshoot from the underground root system (the stool) again the next season. It is possible to continue in this way for several years, until the plants have become exhausted and need to be replaced with new plants. However, an intact root stock is an important prerequisite for ratooning. This is why cane beetle larvae attacking the roots is such a great problem to the farmers.
And have been for decades. As early as the 1930s, there was an attempt at introducing biological control of the cane beetle by introducing the cane toad –originally from South America – to Australia. The assumption was that the cane beetle problem would be controlled when toads became predators of the beetles.. The project was a failure: Unfortunately, Australia now has a toad problem on top of its beetle problem. The supposed solution turned into a prolific and ecologically disruptive intruder.
Later, the sugar cane farmers began to have success with organochlorine and organophosphorus chemicals. Whilst these were effective, they were also problematic: for example the organochlorines had serious environmental consequences, and chlorpyrifos, an organophosphate, is biodegraded very rapidly in many Australian soils – thus rendering it ineffective very quickly. These classes of substances have since been largely replaced by active substances with better risk profiles.
ConfidorŽ Guard became available under emergency permit conditions when control of greyback grub became a catastrophic failure in one of the major growing regions, the Burdekin, in 2001. “At the time, we were actually in the process of developing a special Confidor formulation for use in sugar cane,” recalls Pat English, “but because the active substance in Confidor Guard had a completely new mode-of-action for controlling beetles, we soon found out that we had some better options with a conventional formulation.”
“This product had extremely good residual efficacy which meant we then had options to apply into ratoons as well as in the plant crop, which had not been possible before with any product. We developed new application techniques and equipment which allowed placement below the soil surface in both circumstances. The ability to apply treatments in ratoons has been a revolution in canegrub management,” said English. “What’s also important about the product is that it enters the roots, so it can act systemically,” explains Pat English. As soon as the larvae begin to chew on the roots, they start swallowing the active substance. Confidor Guard is especially effective when taken up into the insect stomach, he points out.
And the Bayer sugar cane team members stress another important aspect: Confidor Guard fits perfectly into Integrated Pest Management (IPM) programs. The active substance is effective at very low doses, and it can also be used very selectively: if applied correctly, its systemic action means that it will have the lowest possible effect on non-target organisms.
Fitting into IPM programs
For the cane beetle, however, Confidor Guard is bad news. As soon as the larvae come into contact with the product, their behavior changes noticeably. “They stop eating and begin to lose body mass,” says English. When this effect remains in place for several weeks, it usually results in the grubs starving to death.
We have also gained much improved knowledge of beetle behaviour says English. “With greyback grubs, we now know how to attract egg laying adults to some cane fields in preference to others. The mechanism is related to the height and vigour of each field, but in essence, we can manipulate the chances of individual fields being infested. Once we do that, we can use some fields as “lethal trap crops” by treating them with Confidor Guard.” Farmers can manipulate height and vigour of individual fields by varying harvest timing, nutrition and irrigation. “It’s actually an elegant implementation of IPM”, says English.
With other grub species, other techniques are used. Grubs with 2-year lifecycles cause damage in spring, and can be effectively treated immediately when the first signs of damage are evident, because the cane is rarely so large at that time that application is not possible. However, those species which have an annual lifecycle tend to cause damage in autumn, which means that often cane is too large for machinery to be operating in those fields. In those circumstances, prophylactic treatments need to be applied in spring well before infestation.
This is exactly the case on Graham Blackburn’s farm. “In autumn, by March and April the stalks are already so high again that we can no longer go over the fields with a tractor in order to treat, therefore, we do a prophylactic treatment each September by injecting directly into the stool,” says Blackburn who has been using Confidor Guard for four years now.
“It does a fantastic job.“
Another important factor in the acceptance of Confidor Guard is that if it is used properly, it presents negligible threat to the Great Barrier Reef Marine Park, which lies offshore, running along the coast (see box). We conducted local “fate” studies with this product and the application methods seem to be biologically effective while limiting offsite movements.
Within only a few years of its introduction in Australia, Confidor Guard has become market leader in sugar cane insecticides. Among many others, Graham Blackburn seems to be quite happy with its effectiveness. “It does a fantastic job. It keeps the cane green where it turned yellow in the years before.” And for the first time in more than 20 years Blackburn has got a better sugar content in his cane than the average of the colleagues in his mill area. This return on investment makes the use of the product “very economical”, as Blackburn puts it.
Knowing such results, Pat English sees even more potential for the product. “There are still areas of this country’s sugar cane industry that are not yet practicing the treatment, but where treatment would certainly bring financial benefits for farmers,” explains English. He and his colleagues still have a lot to do. They help farmers wherever they can. But there’s one problem they have no solution for: they’ll never be able to prevent extreme weather events.
