Integrated pest management can be used to reduce insect numbers in cotton.

This might seem an unusual topic to be discussing in 2017, after all haven’t all advisors and farmers been recommending and using integrated pest management, or IPM, for almost two decades? Isn’t everyone very familiar with the subject? Well no, unfortunately, the extensive use of insecticides in Bollgard crops by so many people in the summer of 2016/17, while those practising a full IPM programme used hardly any, is ample proof of that.

The objective in pest management for all crops, let alone cotton, should be first to take all steps to avoid a pest management problem, but if it occurs, to consider anything other than reaching for an insecticide as the first option for control.

 If anyone has had the good fortune to visit the Singapore gardens, as I did recently, they will find that there are absolutely no biosecurity precautions there whatsoever. Any overseas visitor can walk in with a pocketful of pests, knowingly or not, and at least some would escape. It must happen. Yet insecticides are not used. The pest free status of the gardens is maintained by integrated pest management.       

IPM uses every means available to reduce insect numbers before spraying an insecticide, in particular there is a major emphasis on understanding the rate of natural mortality of both eggs and very small larvae, which can easily be 80% in mid summer, and preserving beneficial insects, which are those insects which eat other insects rather than the plant.

When IPM is used success is guaranteed. When it is not used there is absolutely no doubt that resistance to insecticides will develop, they will become ineffective and substantial profit will be lost.

Every year the scientists in the cotton industry measure insecticide resistance levels in the common insecticides and the only times those resistance levels decrease are when the insecticides have hardly been used in a season.

For about the last decade silverleaf whiteflies have been increasing as the major late season pest of cotton. For those people not practising IPM there have been several insecticide choices to control whiteflies including a very good product called Admiral, which initially was very expensive, over $100/ha, so was used as a last resort. A few years ago it came off patent so now is much cheaper, almost half the price.

Whiteflies were first detected in Emerald in 2008/9. The scientists advised then that the number of generations they would complete in a season was greater in hotter regions. By the time they had completed 7 or 8 generations they would have reached pest status and therefore would need controlling.

Since then they have spread to southern Qld, including the Darling Downs which in 2008/09 was thought to be almost immune from whiteflies because it was not hot enough, and to Narrabri in northern NSW. In fact they have been reported even further south in low numbers.

There would be very few cotton farms in Qld and northern NSW where Admiral has not been used in the last few years. It is highly regarded because it has been very effective. It is a late season cost which has been budgeted for when most costs have been incurred and harvest is relatively near. Therefore it has been widely used in the industry, whether needed or not.

The frequency of resistance to Admiral is far greater in the Gwydir Valley than any other cotton growing region in Australia. Therefore there is far greater misuse of insecticides and much less use of IPM in the Gwydir than anywhere else.

In the summer of 2015/16 resistance to Admiral was detected by the scientists in only some of the samples collected. In 2016/17 there was a large increase in the number of samples showing resistance to Admiral. If resistance continues increasing at that same rate, the scientists believe it is very likely that in two years Admiral will be ineffective.

The whiteflies have been adapting to milder summers. When Admiral is gone it will be impossible to control them with the available insecticides, but it will always be possible to avoid them using full integrated pest management.

The kicker on all this is that there was a far worse pest out there last summer which was also caused by poor insecticide choices and if IPM is not adopted it will certainly become a major problem.

That pest was the mealybug. It must have been far more widespread than was reported in 2016/17 because it has previously always been found where beneficials have been eliminated by the use of broad spectrum insecticides like pyrethroids and Admiral is subsequently used.

Mealybugs are also a white insect, sometimes seen on citrus and ornamentals. Temperature does not appear to be a constraint to their spreading, since they have been reported in Victoria. They might be controlled by neem oil in the garden but that would almost certainly not work in cotton fields.

Sadly, not many people are interested in IPM these days because Bollgard has eliminated Heliothis which was the major pest of cotton. The consequence is the unnecessary spraying of Bollgard, up to 6 or 7 times, in the Namoi and Gwydir Valleys in the past few years. The problem is not confined to the Namoi and Gwydir; it is just worse there.

Using IPM requires planning and an ability to think outside the square. It guarantees maximum profit and sustainable farming enterprises. Growers who use IPM never have a whitefly problem, never use Admiral, always get high yields and never lose yield due to IPM.

IPM is not organic or bio dynamic. It just requires consultants to spend more time in the field and it will reduce the reliance on insecticides.

In 2016/17 the few growers using full IPM at St. George averaged about 2.5 sprays of an insecticide called Transform, and nothing else, in the entire season. It is very specific on aphids and mirids, very soft on beneficials and suppresses whiteflies. There are other options for aphids and mirids which are cheaper to purchase but they cause other expensive problems, such as the whiteflies and mealybugs.

The use of insecticides because they are cheap to purchase is short sighted. It is a ridiculous argument which I hear constantly. No one chooses Belarus tractors instead of John Deere or Mahindra utes instead of Cruisers.

I am aware that the cotton bureaucracy is considering restrictions on the use of Admiral in order to delay the onset of resistance. However I don’t think that just telling people what not to do will make much difference. A complete change of mindset is needed.

The mild winter we are now experiencing is not a good sign for next summer’s pest management. It is very likely that pest management in summer crops in 2017/18 will be a major challenge to advisors and growers not using integrated pest management.

I would be really pleased if people would call me to discuss using IPM in 2017/18. It is just so easy and so productive.

  • John Barber is a consultant at St. George


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