Edward Hagues and Roger Bradbury of the Bayer roots technical team outline the considerations that should influence herbicide choice in sugar beet.
Sugar beet is one of the few crops that supports a wide range of effective grass and broadleaved weed control options. Even for black-grass, a scourge for those on heavier land, the pre- and post-emergence options are far from limited.
Despite an impressive array of products, there are several issues to consider, such as application timing and tank-mix compatibility; both of which can influence performance. Certain phenmedipham formulations, for example, require the addition of an adjuvant oil to soften the leaf cuticle for best performance, but the contribution to improved herbicide effectiveness must first be balanced with the increased risk of crop damage.
The greatest consideration however, is perhaps crop safety. Sugar beet is easily stressed by herbicide applications. It may be an obvious statement to make, weeds are generally more susceptible when rapidly growing and soil moisture levels are good.
A mix of Betanal maxxPro (desmedipham + ethofumesate + lenacil + phenmedipham) and Goltix (metamitron) delivers excellent residual and post-emergence control while being kind to the young crop. The same cannot be said for other three-way products or tank-mix combinations.
Environmental stresses too, such as fluctuating temperatures (a swing in day/night temperatures of 18oC or more) or extreme temperatures (above 21oC), can check crop growth.
Frosts can be damaging too. Not only can they stress the plant, but the wax layers that make up the leaf surface are affected meaning there is increased risk of yield loss if herbicides are applied are during or immediately after a frost. Bright sunshine has a similar effect, and for this reason it is best to avoid spraying in the heat of the day.
In contrast, cool and breezy conditions increase the wax layers on beet leaves which reduces the chances of crop damage. Unfortunately, weed leaves benefit too making them harder to control. Having a herbicide with a formulation that spreads across the leaf and more effectively penetrates this layer is important.
While the range of herbicide options may be impressive compared with other crops, the list of those that offer reliable control of a broad spectrum of weeds with good crop safety is short. As a straight or in a programme, Betanal maxxPro delivers superior performance every time.
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The 2017 season saw many growers reporting high disease pressure with some experiencing control below their expectations.