The lack of rainfall in some areas and swings between night and daytime temperatures are creating challenging conditions for sugar beet weed control this season.
While the dry weather helped growers expedite drilling, with most finished by the end of March, it has slowed crop development and left plants at different growth stages. Hot weather adds to the challenge of knowing when and what to spray for weed control, says UPL head of technical services Stuart Jackson.
“Continuing dry weather coupled with relatively high temperatures is leading to, in some cases, stressed, variable crops and difficult conditions to achieve successful weed control,” he says. “It’s not in every situation. Where growers were able to get a good seedbed, drilled a little earlier, crops are generally looking healthy, and weed control has been good.”
Emerged weeds are generally pretty tough to control because they are waxed up and drought-stressed, adds Stuart. In these scenarios, growers need to load more contact activity into programmes.
“Typical residual mixer partners, such as Venzar (lenacil), are less effective in dry soils, where root uptake is restricted, and should be replaced by more contact-acting herbicides, such as Shiro (triflusulfuron-methyl) and/or Vivendi (clopyralid) to base mixes of Betasana (phenmedipham), plus Bettix Flo (metamitron) + Efeckt (ethofumesate).
“Shiro will be helpful on polygonum weeds and brassicas, while Vivendi is stronger on mayweeds and black bindweed,” explains Stuart.
Oil or insecticides inclusion tips
Stuart believes adding oil to herbicide mixes will help pep up weed control, but it can come at the cost of crop safety. He suggests using the forecast maximum temperature on the day of application to help guide decisions, with anything over 21oC as the cut-off for not adding it into tank mixes.
“Where growers want to use oil at their own risk in temperatures above 21 C, cut rates to no more than 0.5 L/ha and spray first thing in the morning or the evening. If crops have flagged or flopped during the heat of the day, avoid spraying in the evening and leave them until the morning.”
With aphids arriving earlier than originally forecast at the beginning of May, many growers might need to tank mix an insecticide with their weed control spray.
The three insecticides available for use are Teppeki (flonicamid), Insyst (acetamiprid), and Sivanto Prime (flupyradifurone), all of which are compatible with the three-way mix of Betasana, Bettix Flo, and Efeckt.
“What we don’t know yet is the compatibility of Sivanto Prime with the bigger multi-way mixes where you add in Shiro or Vivendi. Insyst or especially Teppeki are better options for grower looking to do that type of bigger mix.
“Obviously, consideration needs to be around the sequence order of the insecticides, which says to avoid using two sprays with the same mode of action in a row. Depending on that, it may be the case of spraying the weeds first, waiting for a few days before spraying the insecticide to give more flexibility.
“For those tank-mixing an insecticide, don’t add oil. However, it may be worth replacing the oil in these conditions with a biostimulant like Vitalroot to help the crop thrive. Vitalroot is a seaweed extract with phosphorus and potassium and can be used at 1-2 L/ha in conjunction with the broadleaf weed herbicide programme. It won’t pep up herbicide activity like an oil, but it will help with crop growth,” he concludes.
