More wheat could mean more wild oats this season. Mike Abram finds out how to improve the performance of a leading product

Following a few simple tips can make popular wild oat killer, Axial, even more effective, according to application and herbicide experts from its manufacturer Syngenta.

The firm has carried out a number of field and laboratory experiments in an effort to optimise the product’s performance, Jason Tatnell, the firm’s herbicide specialist says. “It is all about how to get the best control from Axial given that the wild oat can be a difficult target to hit.”

Timing

The optimum timing, according to Syngenta’s trials database, is GS25-30 of the crop. By that time virtually all of the wild oats should have germinated and the crop canopy is still open to allow the spray to hit its target. Control levels from Axial in trials are nearly 100%, while fenoxaprop also gives high levels of control (96%).

Going earlier risks missing late germinators, and provides a more difficult to hit smaller, upright target. Control in the trials drops with Axial to 93% and fenoxaprop to 85%.

Coverage is the issue with later timings. The crop or large weeds can shade smaller, later germinating wild oats or small tillers making them hard to hit.

But, according to Jealott’s Hill investigations, that’s less of an issue with Axial than some other contact herbicides. Their experiments, where one tiller on a large wild oat plant was covered with a plastic bag to prevent it from being sprayed, showed the ability of Axial to move around the plant was sufficiently strong to still kill the whole plant. In comparison, the tiller on the plant treated with fenoxaprop, continued to grow, Mr Tatnell says. “There was also some re-tillering from the base of the node, which indicates it didn’t receive enough of a dose to kill it. The difference was chalk and cheese.”

It goes some way in explaining why the drop off in fenoxaprop performance (86%) is greater than for Axial (95%) at the later timing, he believes.

Application technique

Syngenta has also put trials efforts into optimising water volumes, nozzle selection, boom height and forward speeds for Axial efficacy and to see the effects on drift, application specialist Ben Magri says.

Five Axial treatments were tested in a 2007 trial, where a heavy wild oat population of up to 200 plants/sq m in wheat were sprayed in late May. Wild oat growth stages were GS21-49. “Small control differences were clearly visible,” Mr Magri notes.

The trials showed water volumes could be cut – but not as low as 50 litres/ha. Control dipped by 2%. “100 litres/ha is optimum there’s no benefit of going any higher.”

Using the low drift Amistar nozzle resulted in a 1% drop in efficacy, but Mr Magri says the benefits of using the nozzle outweighed the loss in performance in this instance. “It gives 75% less drift than a conventional flat-fan. That means you can run with an increase in wind speed of one beaufort unit, which equals four extra spray days in May and four in June. It should also mean you have a better opportunity to hit weeds at the right growth stage.”

Using the correct boom height is also important for drift reduction and also efficacy. Spraying at 1m in the trial knocked efficacy back by 3%. “We think the spray doesn’t penetrate the crop as well.” And just a 30cm rise in boom height from the optimum 50cm gives you a six times increase in drift, he says.

Finally, don’t get caught speeding, he advises. Spraying at 16km/hour again lost 3% efficacy – even at 50cm boom height. “Don’t go above 12km/hour – coverage is the key with getting the best out of Axial.”

Axial best use advice

• Boom height 50cm (no higher than 70cm)
  
• Ideal pressure 2.0 bar (no higher than 2.5 bar)
  
• Water volume 100 litres/ha
  
• Amistar nozzle to reduce drift
  
• Use Adigor at 1% (particularly on large weeds)

New Adigor rate

Syngenta has a new maximum concentration recommendation of 1% for its Adigor adjuvant that must be tank mixed when using Axial. The higher concentration is particularly useful when spraying larger weeds or when there are coverage issues, Mr Tatnell says.

• More information on spring herbicides and plant growth regulators