It's time-consuming, a drain on cash flow, follows yet another poor year for many farmers and comes at a time when most grain producers are considering a well-earned break, but the evidence is indisputable that summer weed control is a crucial task.
Trial work from the Birchip Cropping Group (BCG) shows that in 2008 there was a 50pc wheat yield reduction where weeds were allowed to grow over the summer months.
And with much of the Australian cropping belt receiving heavy rainfall over November and December that will not have been used by the winter crop, there is even more incentive than usual for farmers to control weeds and provide a valuable subsoil moisture bank for the following crop next year.
Research indicates that as a rule of thumb around a quarter to one-third of a summer rain event is available to the following crop.
For instance, a 100mm rain event would leave 25 to 33mm of plant available water next season.
Given the erratic nature of spring rainfall, some farmers in low rainfall zones now describe summer spraying as one of the most important operations of the cropping cycle in providing some moisture for crops should the season turn bad.
This year is no different – in traditional winter-dominant rainfall areas, there is only a slight difference between growing season rainfall (GSR) and non-growing rainfall already, with two months of the summer to go.
BCG technical officer James Jess said the BCG trial site at Curyo received 140mm of GSR, followed by 120mm in late November and December.
Summer spraying is already in full swing through Victoria.
Mr Jess said farmers were looking to control volunteer cereal crops, in particular barley, and traditional summer weeds such as heliotrope, melons, bindii and thistles.
However, another traditional menace, marshmallow, has been slower to get established, with most of the sightings just of small and easily controlled seedlings.
He said it was an unfortunate occurrence that the best time for weed control was when weeds were still small, meaning farmers ideally should be out spraying immediately following the bustle of harvest.
"The cheapest form of weed control is a timely one, which means when you least want to be out on the spray tractor straight after harvest."
Many of the mixes recommended by BCG are glyphosate/2,4-D ester based, featuring other specific additions for targeted weeds, such as Garlon for melons, Goal for marshmallow and Dicamba for wireweed (apart from the chemical exclusion zones near horticultural areas that prohibit the use of 2,4-D).
Mixed farmers can also use livestock to control weeds, although they must be aware of compaction issues should there be following rain.
Mr Jess said lower rates of knockdown chemicals were available to finish the job, while low rates of 2,4-D or Amine had the effect of increasing weed palatability by sweetening them.
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