If cleavers appear in winter oilseed rape weigh up your options carefully before spraying this autumn, advises Dow AgroSciences.
"Warm soils with adequate moisture levels means we can expect a very quick flush of early germinating weeds" says Dow's Colin Bowers. "Many weeds will thrive in these conditions, with mayweed the greatest issue. Growers need to choose the best control programme for their weed spectrum."
Mr Bowers advises using 0.35 l/ha DowShield (clopyralid) for early control of rapidly growing 'soft' mayweed as well as sowthistles - another weed that can threaten crops. Dow Shield can be applied from the two expanded leaf stage of winter oilseed rape.
Reliable early weed control reduces crop competition levels. This is especially valuable in crops established by broadcast and minimal tillage techniques at low seed rates. In such crops there is an increased risk of weed competition leading to inadequate crop stands.
"If cleavers emerge at very high levels in any oilseed rape crops then do consider Galera (clopyralid + picloram), but remember it can only be sprayed once in a season. If more cleavers are expected to germinate in the spring then be patient and wait. A spring application of full rate Galera will also tidy-up any later germinating mayweeds and seedling thistles."
Mr Bowers recommends growers increase rates to 0.5 l/ha if conditions are cooler, or the target weeds are reaching their maximum stage for good control with the reduced rate - four expanded leaves for mayweeds and seedling thistles, and six expanded true leaves for groundsel.
