Abstract/Summary

Weed control in field vegetables in the UK is increasingly challenging due to the loss of herbicide actives and demands by policy makers and consumers for lower pesticide use. Research at Reading University in conjunction with Concurrent Solutions LLC in the USA, is developing a robotic weeder for field vegetables in the UK using image analysis to locate weed leaves and a novel applicator to apply droplets of herbicides to these leaves. No chemical is applied to the crop and none directly to the soil. In glasshouse trials, efficacy of applying one droplet of herbicide per weed was determined. Dose-response relationships for control of Stellaria media L. Vill. with glyphosate and of Chenopodium album L. with glufosinate-ammonium showed ED50s of 3.0 and 4.4 μg per seedling compared to the calculated manufacturers’ recommended doses of 48.8 and 21.9 μg, respectively, for weed seedlings of the sizes treated. The question remains: is this efficacy reproducible in the field? Manually applied droplets of glyphosate were made to the naturally occurring weed population in a transplanted cabbage crop in summer 2016. Efficacy of droplet applications to control weeds and to prevent crop yield loss were assessed in comparison to weed-free (hand-weeded), and weedy controls. Reductions in herbicide were compared with use of the pre-emergence herbicide, pendimethalin, and inter-row glyphosate sprays. Droplet applications 3, 5 and 7 weeks after transplanting reduced residual weed biomass at harvest by 92% compared to the weedy control and gave a crop yield, which did not differ significantly from the weed-free control. At the same time, the total amount of herbicide active ingredient applied was 94% lower than the recommended rate for pendimethalin.