Weeds are a priority

9 Mar 2012

I’ve been speaking at series of meetings in South Australia, New South Wales and Victoria, organised by the GRDC, HGCA’s Australian equivalent. However, the GRDC budget is a little higher at A$110 million (about £75 million). The Government provides GRDC with another A$55 million, so the total budget is A$165 million, which represents about half of the total research spend in grains. This means that researchers are very close to practical issues.

The top research priority is weeds. Annual rye-grass (a different species to UK rye-grasses) has developed resistance to nearly all herbicides, including trifluralin and glyphosate. Hence, their arable systems are near to the edge because of this weed.

This year there is a new pre-emergence herbicide from Bayer called Sakura (ai pyroxasulfone) that currently offers reasonable control; unless seedbeds are dry. Weed scientists say that it’s probably only time before resistance develops to its mode of action. One said that Sakura means cherry blossom and you know how long cherry blossom lasts.

Sakura has a new mode of action to Australian grower. It is being tested in Europe, but not by Bayer; the chance of registration in Europe has to be questioned because of its persistence in the soil. Long persistence also provides a greater opportunity for it to move into water.

In many ways, the rye-grass situation in Australia is very similar to black-grass in the UK. There are no longer any real post-emergence options and it is now all about stacking or sequencing pre-emergence or early post-emergence options. Even then control may be incomplete, so cultural control is being adopted.

One option is to grow more competitive crops, but of course too much crop green matter may put yield at risk if there is a ‘dry finish’. The weed is vulnerable in one respect; about 50% of the seed is still on the plant at harvest. Hence, farmers have adapted combines to collect the seed in a towed trolley or put it through a towed seed crusher. Alternatively,  they have adapted combines to leave a narrow swath called a windrow. These are burnt when the fire risk is low, usually in March or April, three to five months after harvest. The narrow swath creates a higher temperature burn to kill the rye-grass seed harvested with the straw.

Post Office - Australian style

Other problem weeds include the wild radish, the same species as our runch, and fleabanes. Herbicide-resistant wild radish is a major issue in Western Australia and fleabane seems to be increasingly an issue in most arable areas in Southern Australia. Again cultural control measures are being adopted. Some wild radish seed can be collected by the combine and it is vulnerable to burning. However...and keep this to yourselves...some farmers are going back to ploughing to control problem weeds after many years of little or no tillage.

Some of the GRDC meetings I spoke at were held in small country towns. These are in crisis, as witnessed by the number of closed shops. The increased productivity of farming has resulted in a dramatic reduction in employed labour and many farmers have given up sheep because of the poor returns from wool. Frequent droughts over the past ten years have cut down the spend in local shops by farmers, with many smaller settlements now down to a couple of inhabited houses, despite the number of post boxes at the local ‘post office’.