August 11, 2003

Central Queensland Cotton Tales 02
By David Kelly, DEO, Cotton
Queensland DPI/ Australian Cotton CRC

This is a newsletter designed for farmers and consultants in the cotton industry in Central Queensland. Not all information is relevant for other areas.

As most people would be aware, for the 2003-04 season growers cannot grow more than 25% Ingard® and a combined area of Ingard®/ Bollgard II cannot exceed 40% of the total farm unit.

The reason for this is resistance management.

The current Ingard® varieties produce one Bt toxin, Cry 1Ac. The Bollgard II varieties produce two Bt toxins Cry 1Ac and Cry2Ab.

Australian cotton producers have experienced the difficulties of Helicoverpa armigera developing resistance to synthetic pesticides – it has done so to almost every major group of chemicals (pyrethroids, carbamates). The Bt proteins expressed in Bt cotton plants are NOT immune to
resistance. 

The fact that a strain of Helicoverpa armigera has been selected in the laboratory to be resistant to Cry1Ac, by the CSIRO, demonstrates this. In this study, led by Dr Ray Akhurst, CSIRO Entomology, Canberra, Helicoverpa grubs collected from cotton crops were fed on a diet containing Cry1Ac protein. Surviving insects were selected out and bred. As the graph above shows, after 21 generations,
resistance levels had risen to a level where the insects were over 300 times more resistant to Cry1Ac than a susceptible laboratory population. (Full report in Australian Cotton Grower Magazine, Nov- Dec 1999).

Bt is naturally present in the environment and therefore it is likely that even prior to the introduction of Ingard® that there was a very low frequency of H. armigera moths that had some degree of resistance to Bt.

Bt cotton with just one Bt protein (Ingard®) was never intended to be a long-term product – due to the risk of resistance. Ingard® was only ever meant to be a steppingstone to a much more sustainable two-Bt gene product (such as Bollgard II), which was originally expected to be available within 4 years of Ingard® being released (3 years ago).

The components of our resistance strategy such as the cap on Ingard® area, sizes of refuges, pupae destruction and trap crops have been evaluated with the aid of theoretical models, which integrate all that we know about Helicoverpa, their populations, and how they develop resistance.

The same models show that two gene Bt cottons (Bollgard II) can bring a huge pay-off in protection against Bt resistance. Such products should last 5-10 times longer than Ingard® cotton, provided we don’t have field resistance to CryIAc before they are released.

The longer our Helicoverpa populations are exposed to the CryIAc on its own (Ingard®), the shorter the expected lifespan for Bollgard II will be, hence the necessity for a rapid change from Ingard® to Bollgard II.

‘Flexible’ Planting Window for Ingard®/ Bollgard II for Central Queensland

The Central Highlands Cotton Growers & Irrigators Association recently wrote a letter to the Transgenic and Insecticide Resistance Management Strategy (TIMS) Committee asking for the ability to use a ‘flexible’ 6-week planting window for Bollgard II and Ingard® within a specified 8 week period (15 Sept to 15 Nov). The purpose of this was to increase the chances of making use of summer rainfall.

The TIMS committee has no objections to this proposal as long as it is properly administered on a local level. The steps from here to achieve approval for the “Flexible Planting Window” for the 2003-04 season include:

(i) All known Central Highland cotton growers must sign a letter from Monsanto indicating unanimous agreement for the concept (Monsanto will be faxing this letter shortly).

In signing this letter growers also agree to abide by the final planting dates when these are set by the Central Highlands Cotton Growers Research & Technical Group and also agree to sign to indicate receipt of a subsequent notice advising of these dates when it is sent by Monsanto.

(ii) Monsanto will then make application to the Agricultural Pesticides and Veterinary Medicines Authority (APVMA) with the TIMS letter (Monsanto must have unanimous grower agreement to proceed) to seek approval for this licence change. There is no guarantee that approval will be given in which case the existing arrangement (i.e. 15 Sept- 31 Oct) will apply.

(iii) Monsanto will notify growers of the outcome of the APVMA application.

(iv) If successful the Central Highlands Cotton Growers Research & Technical Group will organise the setting of dates as the season unfolds.

(v) Monsanto will send a notice (refer point (i) above) advising of these dates and this must be signed to acknowledge receipt of the notice.

(vi) If the AVPMA agree to this then adherence to the dates will be a legal requirement.

NOTE: The Dawson Callide has also been included in this application, although the timing of its window will not need to be the same as the Central Highlands. The dates will be set jointly by the Dawson and Callide grower associations.

What now?

• The Central Highlands Cotton Growers Research & Technical Group will meet next Wednesday to discuss how the flexible planting date might me administered in the Central Highlands.

• Feedback from the Dawson Callide would suggest they will stay with the current window (15 Sept- 31
Oct) because of the current water year arrangements, but the flexibility is there to move if there is a need.

• The planting window for Ingard® and Bollgard II in Belyando remains 10 Oct- 25 November (as it was last season), although an application has been made to TIMS by growers in that area to delay this.

For further information, visit Cotton Tales at http://www.cotton.crc.org.au/