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Read the latest news from Bayer CropScience Australia.

01 March 2011

Bayer CropScience offers advice on managing defoliation

Melbourne, 1 March 2011 – Australian cotton growers may need to adjust harvest aids for crops this season as the climate patterns have caused variation of cotton within fields which has the potential to play havoc with timing, product and rate choice for defoliation.

A cooler, wetter growing season, particularly from October to December and in some locations extending into early January, has presented a number of challenges for Australia’s cotton growers.

"Climatic conditions this season have led to delayed crops, later crops, and variation in crop stages within fields, all of which will affect the successful removal of leaf material and the opening of mature bolls at defoliation this season,” says Don Biffin, Senior Development Specialist at Bayer CropScience.

Bayer CropScience has a range of harvest aids to assist with defoliation, including Dropp® Liquid, Dropp® UltraMAX and Prep®.

“Australian cotton growers will face a challenging defoliation this season. This is not the season to stick to your ‘tried and true’ defoliation recipe.”

“Growers should be aware of climatic conditions, temperatures and crop condition, and make defoliant type and rate decisions based on this,” Don comments.

“Where cotton is stressed, either from water logging or drought, translocation of water and nutrients is restricted and as such defoliation may be slow and less effective than normally expected under good growing conditions,” he explains.

“Stress also decreases the effect of defoliants and growth regulators on new growth and immature bolls,” he adds.

“In situations where the crop is stressed or where the crop has high levels of nutrients and water available, the addition of Prep 720 to either Dropp Liquid or Dropp UltraMAX will assist with the removal of new growth and immature bolls.”

Kim Bremner, an irrigation farmer from the Darling Downs, points out that a critical issue this season would be the variation of plant maturity within fields.

“Flood water and rainfall has affected the plants and with the high degree of variation within fields it's a matter of working out when to defoliate to get the best returns.”

To address these challenges, cotton growers will need to adapt and change tactics as climate, temperature and crops dictate.

Discussing the Bayer CropScience range, Don explains, “In some areas where crops have been delayed or replanted, they will be defoliating later than usual and they need to be wary of temperatures at defoliation.

“If temperatures are too low to get optimal results from Dropp Liquid, growers may need to switch to using Dropp UltraMAX.

“It may also mean that where conditions are still favourable to the use of Dropp Liquid, they may find that they require higher rates compared to previous seasons, because of stressed cotton or a later defoliation.”

Reflecting on his experience, Mr Bremner adds, “Last year we used Dropp Liquid, but when the conditions and weather patterns changed we went back in with Dropp UltraMAX and that cleaned it up well.”


1. To maximise efficacy, always apply the recommended rate of oil or adjuvant with harvest aids to ensure good coverage and penetration.

2. When there are high levels of nutrients and water in the soil profile at defoliation, particularly where the crop carries very heavy leaf canopy, three applications of harvest aids may be required. In such cases, the addition of Prep 720 to either Dropp Liquid or Dropp UltraMAX can assist with the removal of new growth and immature bolls.

3. Where leaf freeze is a concern in hot conditions (30-35ºC), use Dropp Liquid towards the lower end of the rate range recommendation, provided that the application and rate matches the crop and environmental conditions.

4. If the cotton is drought stressed, apply defoliants in the early morning rather than in the late afternoon as the plants are slightly more turgid at this time (ie. they are less limp at this time due to the possible overnight dew). Do not apply during the heat of the day.

5. When facing waterlogged conditions, use the higher end in any set rate range suggested by the agronomist or consultant.

Note:The addition of organophosphate insecticides or glyphosate to harvest aids can cause leaf freeze.

For more information on managing defoliation this season, contact:
Don Biffin, Senior Development Specialist
M 0417 370 798

About Bayer CropScience
Bayer is a global enterprise with core competencies in the fields of health care, nutrition and high-tech materials. Bayer CropScience AG, a subsidiary of Bayer AG with annual sales of about EUR 6.5 billion (2009), is one of the world’s leading innovative crop science companies in the areas of crop protection, non-agricultural pest control, seeds and traits. The company offers an outstanding range of products and extensive service backup for modern, sustainable agriculture and for non-agricultural applications. Bayer CropScience has a global workforce of 18,700 and is represented in more than 120 countries. The Australian head office is located in Melbourne.

Media Contact
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T +61 3 9248 6851
M +61 448 817 842

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This release may contain forward-looking statements based on current assumptions and forecasts made by Bayer Group or subgroup management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Bayer’s public reports which are available on the Bayer website at The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.


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