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How much damage can ratoon cotton do?

Effective crop destruction is an important part of the management of a Bollgard 3 system.

Ratoon cotton poses a resistance risk as it extends the amount of time Helicoverpa are exposed to the toxins contained in Bt cotton outside of the cotton growing season. Ratoon cotton is a host for pests and diseases. Pests such as aphids, silverleaf whitefly and mealybug can use ratoon cotton to survive over winter and re infest the following cotton crop. Ratoon cotton can also carryover disease such as verticillium wilt, black root rot and fusarium. In other crops and subsequent cotton crops, ratoon cotton is considered a weed and can affect yield through plant competition.

Under the Bollard 3 resistance management plan (RMP), all crops must be destroyed by cultivation, root cutting or herbicides so that they do not continue to act as hosts for Helicoverpa. 

Ratoon cotton is best managed post harvest with an effective root cutting and mulching operation after picking. A follow up pupae busting operation or cultivation will further assist with ratoon destruction if required.

Ratoon cotton is very difficult to control with herbicides, especially in other broadleaf crops. Ratoon cotton plants have a very small leaf area compared to a large root system. Heavy cultivation can be effective in destroying ratoon cotton, however this may not be a preferred option in a dryland system, or if the ratoons are within a rotation crop.

The simplest and most cost effective way of controlling ratoon cotton is to prevent it occurring in the first place.

There are now chemical options available for growers and consultants who have ratoon cotton appearing the following season amongst stubble or in fallows. 

As part of an integrated weed management strategy, recent CRDC-supported research (conducted by QLD DAF with support from Nufarm), has identified three herbicide options for the control of large volunteer or ratoon cotton plants in fallow using an optical spot spray technology (eg. WEEDIt, WeedSeeker) providing high plant mortality in the research trial. 

These options have recently been registered for both optical booms and broad acre application, which means all growers should not be able to make use of these options. The product use must be in accordance with the label instructions

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