Knapsack sprayers are popular because of their mobility and ease of use in challenging of terrains but also as an effective method of managing unwanted additions to swards, says Dave Gurney, Corteva Agriscience's Field Technical Manager for Grassland Crop Protection Products.

He says: "Although a useful tool, to legally use a knapsack sprayer, you must have PA1 and the appropriate PA6 qualification for the job being undertaken."

Knapsack sprayers can be particularly useful where access is poor, weed populations in a field are below 5%, or where there is no access to a boom sprayer.

When applying a herbicide, it is important a product is chosen which targets the specific weeds you want to control while also being safe for the surrounding grass.

Dave says: "Plan your spraying activities during periods of active weed growth and before the weeds have started flowering for maximum effectiveness. Spraying during windy conditions should be avoided to prevent herbicide drift onto the spray operator and non-target plants."

There are few selective herbicides which have authorisation for handheld equipment use.

Dave explains: "Grazon^® Pro from Corteva is one of the products licensed to be sprayed through a knapsack. It is an excellent solution for docks, nettles, thistles, brambles and other woody weeds. It can be applied using the hand lance on an ATV mounted sprayer.

"The dose rate is 60 ml in 10 litres of water, so a one litre pack of Grazon Pro provides for 16 knapsack fills of 10 litre capacity."

When handling chemical concentrate, the label instructions should be read and followed carefully to ensure the appropriate PPE is worn, and proper dilution of the herbicide. Store and dispose of herbicides properly to prevent environmental contamination.

Dave says: "Use the spot-spraying technique to apply Grazon Pro to the weeds by aiming the spray directly at the foliage of the target weeds, and spraying up to, but before the point of run-off.

"It should be noted Grazon Pro does not control ragwort. If treated, ragwort will become palatable to animals and the seven day stock exclusion interval will be greatly increased while waiting for the ragwort to recover and become unpalatable again."