A survey of over 200 spray operators revealed that post-emergence grass-weed control in wheat is one of the hardest spray targets for both timing and accuracy. With applications of Pacifica Plus and Monolith against black-grass imminent, here are six essential steps to get the most effective application this spring.
Make sure the sprayer is ready to go at short notice. Spray windows can be short so don’t lose time adjusting the sprayer when you could be out in the field. Check boom stability, nozzles and filters well ahead of time so no opportunity is wasted to control black-grass.
Dew is the enemy at this time of year. You have to wait until it dries off before applying the herbicide and then leave a long enough drying window before dew formation in the evening. Don’t be tempted to apply to a wet leaf because the herbicide can simply run off onto the ground rather than dry and be taken in by the black-grass.
Still days are at a premium and compromises may be needed to get the right timing. Post-emergence herbicide applications may end up being in windier conditions than you would like. Ideally, a post-emergence herbicide is applied as a fine–medium spray with a flat fan nozzle. However, when it’s a little windier an air inclusion nozzle is a better choice to reduce drift.
50cm above the ground is the magic number for boom height. Contact acting herbicides need to land on the target which may be a small black-grass plant at only GS13. Any higher than 50cm and the amount of drift increases thereby reducing efficacy. Lower forward speeds (maximum 12 km/h), a well-maintained sprayer boom levelling system and an even soil surface all enable uniform application at the correct rate.
This season sees Pacifica Plus (mesosulfuron + iodosulfuron + amidosulfuron) propoxycarbazone) widely available for the first time. It has a good spectrum of activity against all main grass weeds targets and the addition of amidosulfuron provides good control of common broad-leaved weeds including cleavers, common chickweed, mayweeds and charlock. In situations where only grass weeds are an issue, growers have the option of Monolith (mesosulfuron + propoxycarbazone). Use Pacifica Plus and Monolith with 1 L/Ha of the adjuvant biopower to get the best results.
With heavy spring workloads, tank-mixing is always tempting to save time. Unless it’s completely unavoidable, tank mixes should be simple and focus on one set of targets to maximise efficacy. For Pacifca Plus, adding residual protection is an option but be cautious with other tank-mixes.
Monolith is a new post-emergence herbicide formulated to tackle black-grass. For use in winter crops during spring, it provides 10% more control than Atlantis against black-grass.
A highly active herbicide (a combination of three sulfonylurea herbicides) with foliar and some root activity against black-grass, wild oats, rye-grasses, bromes, meadow-grass, cleavers, common chickweed, mayweeds, charlock and volunteer oilseed rape in winter wheat.