The lack of rain has been a challenge for those looking to control weeds in sugar beet crops, exasperated by the significant difference in day and night temperatures.
While drilling has gone well, the dry conditions have slowed crop development, with many crops being at variable growth stages. The high temperatures have only added to the challenge of knowing when and what to spray.
“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,” says Stuart Jackson, head of technical services at UPL.
“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.”
He adds that the weeds which are emerging are generally pretty tough, waxed up and drought-stressed. This means growers will 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.”
“For example, you can look to add products 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.
Adding oil or insecticides
Adding oil to the herbicide mix might help with weed control, but can risk crop safety. The maximum temperature should dictate this, with oil being avoided if temperatures are forecast to exceed 21 degrees.
“Where growers want to use oil at their own risk in temperatures above 21oC, 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.”
As aphids are arriving earlier than forecast, many growers might also look to add an insecticide. There are three available for use: 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 if you’re looking to do that type of bigger mix.
“Obviously, you also need to consider advice 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.
“If you are 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,” concludes Stuart.