Spinach growers take charge of future weed control

Spinach growers require new effective weed control since the changes in authorisation for Venzar 500 SC (lenacil) restricting the rate and timing of application, and following the loss of Pyramin DF (chloridazon) and Intruder (chlorpropham). Therefore since 2018, finding solutions to fill these gaps has been a priority for the SceptrePlus program. For the 2020 herbicide screens for spinach growers a different approach was taken to the usual trial design. In standard efficacy trials a number of products are screened in a replicated trial at just one, or perhaps two sites. This gives high statistical confidence, but limited information on the results of the products’ behaviour in different seasonal, geographical and environmental conditions.

In 2019, spinach growers experienced crop damage from napropamide in late season crops and when weather was very wet. This was unexpected, and due to the previous limited test trial conditions there was no indication that crop damage would occur in these conditions. Therefore for the 2020 trials it was decided that a useful approach would be to trial at least the five most promising products selected from the 2018 and 2019 trials in a wider range of situations. To do this, the products and trial applications were handed over to the growers to apply using their own equipment, using either tractor-mounted, self-propelled or precision knapsack sprayers. With spray application equipment now being much more precise, with features such as section control it was possible to apply the treatments using commercial equipment.

Eleven growers took part in the trials, and followed an application and assessment protocol written by ADAS weed research consultant Angela Huckle. The trials were geographically spread across the UK from the North West to the South East and at many sites in between, and covered the season from June to October. This has given Angela a wealth of information in different soil types and environmental conditions with crop and weed responses varying between sites. For example, many products have looked safe at a number of sites, and then at one or two sites they have not been safe. Initially Angela has noted that extremes of weather conditions - either hot or wet situations have exacerbated the sensitivity to the herbicides where they are on the margins of crop safety. Soil type is also being evaluated to determine if it has an effect on increasing the risk of damage from selected products. Efeckt 0.5 L/ha and AHDB 9918 appear to be promising products and the safest in all the trials, and AHDB are looking into EAMUs for these products in spinach crops.