The potato planting and sugar beet drilling season are on their way with soils starting to dry and some drier weather forecast, at last.
With that in mind, planning some weed and disease control programmes for the early part of spring will be beneficial for sugar beet and potatoes.
With sugar beet, pre-ems have been less important in recent times as our current post-emergence armoury has been effective. However, desmedipham-based products are in their last season of use, so we need to change the way we approach sugar beet weed control. These products gave us a margin for error with timing as they would control larger weeds.
Where are we with pre-emergence herbicides? Chloridazon, a long-term favourite and, for many years, a very inexpensive option, is in its last season of use. Stocks on-farm are already generally low and the last date of use for these is June 30.
Lenacil used to be applied in conjunction with chloridazon and was an effective combination if the dosage was correct for the soil type.
Some of you will remember Varmint, which was a combination of lenacil and chloridazon and was very effective, but could cause some damage if the dose rate was wrong. Lenacil now however can only be used as a post-emergence product from BBCH10 or fully expanded cotyledons since its label change.
So this leaves us with ethofumesate, metamitron, quinmerac and dimethenamid-p in various combinations.
Ethofumesate is mainly for grass and is essential on fields with a black-grass issue but remember, only 1,000g active per season. Metamitron will be the mainstay and brings good early control of knot-grass and fat hen, and then the others mixed and matched to best effect according to their weed spectrum.
In potatoes, a robust pre-em can also save a lot of problems post-emergence on most soil types, where the options are quite limited.
We’ve got aclonifen available more widely this season, so that will bring some extra robustness to most programmes.
In addition to aclonifen we have metribuzin, metobromuron, pendimethalin, clomazone and prosulfocarb – so a good armoury of products to mix and match to soil types and weed spectrum.
Of course, we still have the normal precautions and can’t be over-robust in all situations.
Metribuzin still has its issues especially on lighter soils and with certain varieties. Three-way mixes including clomazone still need to be applied within two weeks of planting for good crop safety.
We’ve also got to consider the loss of diquat and what effect that will have. Ever since I’ve been involved in the industry, diquat, and before that paraquat, were the standard pre-em contact material.
However these are no longer in use and the replacements carfentrazone and pyraflufen-ethyl, while still being very effective, are different in their weed spectrum and effect on the crop. These will need to be applied earlier at the very early emergence or preferably pre-em stage.
Some may consider loading up the pre-em soon after planting and then apply the contact alone or with some more residual just prior to emergence.
For the blight programme, I recommend some Zorvec (oxathiapiprolin) in one form or another during rapid canopy growth, to get the whole thing off to a good start, which will relieve pressure at other times of the season.
So, there is a lot to consider but, realistically, the most important things are to keep washing our hands, maintain social distancing and follow the Government’s guidelines on tackling the coronavirus epidemic. Just because we live and work in the countryside, it does not make us less vulnerable.