In many EU countries, spray applications should comply with increasingly stringent requirements regarding the drift reduction class of spray nozzles. Many farmers fear that the use of drift-reducing nozzles producing coarse droplet spectra may compromise the performance of contact herbicides on small weed targets. This study examined the effects of various ISO 03 drift-reducing flat-fan nozzles (pre-orifice and single and dual flat-fan air induction nozzles) differing in spray drift reduction class and spray pressure (2.5 bar, 5.0 bar) on (1) spray coverage, (2) droplet characteristics and (3) efficiency of contact herbicides bentazon and phenmedipham against cotyledon and 2-leaf stage plants of Chenopodium album and Solanum nigrum. Performance was compared to that of an ISO 03 standard flat-fan nozzle producing a finer droplet size spectrum. All sprayings were performed at a spray volume of 200 L ha⁻¹. In most dose–response experiments, several drift-reducing flat-fan nozzles performed equally well as standard flat-fan nozzles, regardless of herbicide, spray pressure, growth stage or weed species. However, droplet size spectra of air-induction nozzles were too coarse for an adequate spray coverage and efficient application of contact herbicides on cotyledon stage plants of S. nigrum. In addition, the performance of air-induction nozzles in controlling difficult-to-wet C. album weeds with phenmedipham was better at 5.0 bar than at 2.5 bar. In contrast with droplet size characteristics, spray coverage characteristics determined on water sensitive papers were not good proxies for estimating the biological efficiency of contact herbicides. Air induction nozzles at 5.0 bar allow efficient control of 2-leaf targets, but nozzles emitting finer droplet spectra, such as pre-orifice nozzles, should be preferred for controlling cotyledon stage weeds at low-herbicide doses.

Cyperus esculentus is an invasive troublesome neophyte in many arable crops across the globe. Analysis of the genetic and morphological profile of local C. esculentus clonal populations may be useful in explaining differential herbicide sensitivity found among distinct clonal populations and spatial distribution patterns. In this study, 35 Belgian C. esculentus clonal populations, evenly spread across the entire infestation area (30,689 km²) and covering a great diversity of farm and soil types, and hydrological and environmental conditions, were genetically characterized using amplified fragment length polymorphism (AFLP) profiling. These clonal populations were also grouped into different morphological clusters using data from shoot, tuber, and inflorescence number, fresh tuber biomass, individual fresh tuber weight, and number of germinable seeds collected in three consecutive years. Of the 271 AFLP markers, 207 were polymorphic. The gene diversity among clonal populations was 0.331 and three genetically distinct clusters were identified. Depending on observation year, clonal populations were grouped in four to five morphologically distinct clusters that closely aligned with the genetic clusters. The genetically distinct clusters differed in their geographical distribution pattern and range as well as in their morphological characteristics. Clonal populations belonging to clusters with broad distribution ranges produced numerous viable seeds. Clusters with clonal populations that produced large tubers were less widespread than the cluster with clonal populations producing many small tubers. The results suggest that tuber size, tuber number, and fecundity may all play an important role in the spread of C. esculentus. Morphotyping may be very useful in designing effective preventive and curative C. esculentus management strategies.

Weed control in organic spinach for the processing market is challenging because of the low tolerance of weed contamination in the harvested produce and the limited physical weeding options. Optimisation of weed control systems is therefore urgently needed. Three field experiments with autumn spinach were carried out in organic fields to evaluate the impact of cultivar choice, seeding rate (300 and 400 seeds m⁻²), plant spacing management (10.5-cm-wide single rows and 21-cm-wide single or twin rows) and integrated weed management strategy (combinations of pre-sowing, pre-emergence and post-emergence tactics) on weed biomass and spinach yield and quality. Spinach cultivars with a planophile growth habit and a high growth rate were more weed suppressive than the cultivar with an erectophile growth habit and a slower growth rate. Spinach density was significantly negatively correlated with weed biomass and weed biomass fraction in the harvested produce, but significantly positively correlated with (marketable) spinach biomass and petiole fraction in the harvested produce. Narrow row spacing systems with post-emergence broadcast harrowing had the lowest weed biomass and weed biomass fraction but also the lowest (marketable) spinach biomass as a result of the thinning action of harrowing. Post-emergence harrowing is of key importance for reducing weed biomass in any integrated weed control strategy. Weediness was lowest in systems comprising flaming on false seedbed or in pre-emergence followed by post-emergence harrowing. To mitigate the risk of crop failure, the field should preferably be cropped with quickly growing spinach plants arranged in narrow spaced rows at high plant density and weeded by pre-sowing or pre-emergence flaming followed by post-emergence harrowing.