Differences in growth and herbicide sensitivity among Cyperus esculentus clones found in Belgian maize fields

Cyperus esculentus is an invasive troublesome neophyte in many arable crops in Belgium. Applied weed control varies from field to field. One of the possible reasons for this variability might be a differential vegetative and reproductive behaviour among Belgian C.esculentus clones. In this study, growth characteristics and herbicide sensitivity of C.esculentus clones collected in Belgian maize (Zea mays) fields were evaluated. In a morphology Experiment, 25 clones were screened for growth characteristics and ability to set viable seeds under outdoor conditions. Dose-response experiments were conducted in the glasshouse to evaluate the effectiveness of two foliar-applied herbicides (bentazon and glyphosate) and two pre-sowing soil-incorporated herbicides (S-metolachlor and dimethenamid-P) for controlling 14 C.esculentus clones. Response variables were aboveground dry biomass, tuber number, tuber dry biomass and individual tuber dry weight. Clones exhibited large differences in shoot number (up to 3.1-fold), tuber dry biomass (up to 4.7-fold), tuber number (up to 3.4-fold), individual tuber dry weight (up to 4.8-fold), inflorescence number and capacity to set viable seeds. Large interclonal differences in herbicide sensitivity (up to 8.3- and 4.0-fold for aboveground dry biomass and tuber dry biomass, respectively) were observed. Contrary to foliar-applied herbicides, soil-incorporated herbicides were very effective and provided season-long C.esculentus control at doses below the recommended maximum field dose. However, low doses stimulated tuber formation. Future C.esculentus management strategies should take into account differential growth characteristics and herbicide sensitivity of C.esculentus clones

Optimisation of weed control in organic processing spinach (Spinacia oleracea l.) : impacts of cultivar, seeding rate, plant spacing and integrated weed management strategy

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

Impacts of herbicide sequences and vertical tuber distribution on the chemical control of yellow nutsedge (Cyperus esculentus L.)

Cyperus esculentus is an invasive perennial sedge threatening agricultural production. In Belgium, best in-crop control options involve, amongst other methods, growing maize in monoculture which allows the sequential use of selective herbicides with activity against C. esculentus. Two pot experiments were carried out to investigate the effect of genetically different clones and chemical control strategy on C. esculentus control. Additionally, the effect of two vertical tuber distributions (uniform in the 0-26 cm layer or non-uniform with 60% of the tubers in the 6 cm top-layer) was studied. Strategies were based on S-metolachlor, dimethenamid-P, mesotrione, bentazon, pyridate, nicosulfuron, glyphosate, halosulfuron-methyl, foramsulfuron and thiencarbazon-methyl used in mixture and/or sequence and applied at different crop stages. Control efficacy was measured by analysing tuber number, dry tuber biomass and above-ground dry biomass. Tuber number of clones treated by chemical control strategies was up to 100% lower and up to 41% higher relative to the untreated control. Clones showed up to 74% percentage point difference in control of tuber number. In both experiments, strategies with pre-plant incorporated dimethenamid-P followed by two post-emergence applications of mesotrione and pyridate, in 5-6 leaf and 8-9 leaf stage of maize, was most effective and consistent across C. esculentus clones. In general, C. esculentus control was up to 27% better in plots with high proportion of superficially buried mother tubers than in plots with more uniform vertical mother tuber distribution. Hence, the vertical tuber distribution may significantly affect the performance of C. esculentus herbicidal strategies. Overall, chemical control strategies should be complemented with alternative methods (e.g. competitive cropping systems and non-inversion tillage) to achieve satisfactory control

Genetic and Morphological Variation of Belgian <i>Cyperus esculentus</i> L. Clonal Populations and Their Significance for Integrated Management

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

Effects of soil and crop management practices and pedo-hydrological conditions on the seedbank size of Galinsoga spp. in organic vegetable fields

Galinsoga quadriradiata and Galinsoga parviflora are very troublesome weeds in many organic vegetable crops in Europe. A very straightforward method to keep Galinsoga infestations under control is by targeting the Galinsoga seedbank. To identify cropping systems able to reduce the seedbank size in vegetable-based cropping systems, the relationships between the seedbank size of Galinsoga species and prevailing soil/crop management practices and pedo-hydrological conditions were investigated. Hereto, the seedbank of the 0-20 cm topsoil layer was sampled in 50 organic vegetable fields and analysed according to the seedling emergence method. Field history data were collected for the past 5 years, and physical, chemical and microbial soil quality was determined. Galinsoga quadriradiata was the most frequent and abundant Galinsoga species in the weed seedbank. The genus Galinsoga was present in 90% of the soil weed seedbanks of organic vegetable fields but displayed wide variation in abundance. Smallest Galinsoga seedbanks were found in fields that were predominantly tilled with non-inversion implements or rotationally ploughed, and continuously cropped with competitive crops during the entire growing season (April 15-November 15). Contrary to G. quadriradiata, seedbank size of G. parviflora was closely related to soil organic carbon content and sand fraction. Remarkably, soils with a low level of easily plant-available phosphorus and concomitant high activity of arbuscular mycorrhizae had smaller G. quadriradiata seedbanks. To reduce Galinsoga infestations, fields should preferably be tilled without soil inversion, fertilised with organic amendments with low content of readily plant-available phosphorus and cropped with competitive crops all season long