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Post crop management

 

Pupae destruction

Pupae trail

To mitigate the risk of resistance to the Bt proteins expressed in both Bollgard® 3 and Bollgard II®, each grower of Bollgard 3 must undertake Helicoverpa spp. pupae destruction in fields with a higher probability of carrying over wintering pupae.

Once mature, Helicoverpa spp. larvae burrow into the soil and pupate as part of their developmental cycle prior to emerging as a moth. From early autumn, the pupae can remain dormant and not emerge until spring when the soil temperatures and day lengths have increased.

This makes the end of the growing season, once the crop has been harvested, the ideal opportunity to target any surviving Helicoverpa spp.

Pupae destruction follows these three key criteria:

  • If the first defoliation of a Bollgard 3 field occurs on or before March 31, the Bollgard 3 field must be slashed or mulched and controlled to prevent regrowth within 4 weeks of harvesting.
  • If the first defoliation of a Bollgard 3 field occurs after March 31, the Bollgard 3 field must be slashed or mulched and controlled to prevent regrowth within 4 weeks of harvesting and pupae busting must be complete by July 31 for all valleys except for regions including the Lachlan, Murrumbidgee, Menindee and Murray Valleys where pupae busting must be complete by August 31.
  • Ensure disturbance of the soil surface to a depth of 10 cm and to a distance of 30 cm both sides of the plant line

Control of volunteer and re-growth Roundup Ready Flex, Bollgard 3 and Bollgard II cotton

Cotton VolunteersVolunteer and ratoon cotton may impose additional selection pressure on Helicoverpa spp. to develop resistance to the Bt proteins Cry1Ac, Cry2Ab and Vip3A produced by Bollgard 3 cotton.

The presence of Bollgard 3 volunteers/ ratoon cotton in any refuge will diminish the value of the refuge and must be removed as soon as possible for all fields including fallow areas.

As soon as practical after harvest, Bollgard 3 cotton crops must be destroyed by cultivation, root cutting or herbicide so that they do not continue to act as hosts for Helicoverpa spp.

Note: The refuge should preferably be planted into fallow or rotation fields that have not been planted to cotton in the previous season.

Central Queensland

Crop destruction

All Bollgard 3 crops must be slashed or mulched and controlled to prevent regrowth within 4 weeks of harvesting.

End of season management of refuges/trap crops

End of season pupae busting practices are not effective in the Central Queensland region as Helicoverpa spp. are less likely to diapause.

A late summer trap crop (pigeon pea) is required for all Bollgard 3 cotton grown in Central Queensland. The entire pigeon pea refuge can be utilised as a trap crop or a 1% trap crop must be planted. The planting configuration of the trap crop should be the same as that of the Bollgard 3 crop.

Dryland Bollgard 3 growers who do not have any irrigated cotton on their farm should contact Monsanto Australia for alternative options.