FarmTalk #10 – Summer Weed Control – Options for the Mallee

Fact Sheet #10 – Feb 2004

Vanessa Grieger – Research Consultant, Rural Solutions SA
Graham Fromm – Field Crops Consultant, Rural Solutions SA

The issue
Summer weeds are a constant management issue that confronts farmers in the mallee. In the era of the long fallow, weeds were controlled by cultivation. However, with the shift towards minimum till and no-till, the following questions concerning control options have been raised –
• Should summer weeds be ignored and dealt with at seeding time?

OR
• Should they be controlled during the summer and if so, at what stage?

Dealing with summer weeds in our current farming systems raises even more issues. For example:
• machinery blockages can occur at seeding time if vine weeds such as melons and caltrop are left to grow;
• stock poisoning is a potential concern if Potato weed (Heliotropium europaeum) and Caltrop (Tribulus terrestris) are left to be grazed; and
• stock handling and wool contamination become a problem if Innocent weed (Cenchrus longispinus) is not controlled.

Therefore, if we decide to implement a summer weed management program, what are the best control options?
• Do we revert back to mechanical control and run the high risk of wind erosion? OR
• Do we use some form of chemical control? That raises the issue of what stage of weed growth should be targeted for optimal control to be achieved.