M. Jursík

Efficacy and Selectivity of Pre-emergent Sunflower Herbicides under Different Soil Moisture Conditions

Chenopodium album, Echinochloa crus-galli, Amaranthus retroflexus, Mercurialis annua, and Solanum physalifolium ) was only slightly affected by the soil moisture and these herbicides can be used in arid and semiarid regions. The efficacy of linuron, prosulfocarb, and pethoxamid was strongly affected by soil moisture and was insufficient under dry conditions. The majority of herbicides showed good selectivity for sunflower. Crop injury rate of 5–15% was recorded after application of flurochloridone and ace tochlor. For flurochloridone, the phytotoxicity increased due to irrigation after herbicide application. The highest sunflower injury rate (27–35%) was recorded after application of oxyfluorfen.

POST Herbicide Combinations for Velvetleaf (Abutilon theophrasti ) Control in Sugarbeet

Abstract Velvetleaf is one of the most significant and fastest spreading alien weeds in Europe, and it is a difficult weed to control in conventional sugarbeet. Laboratory experiments were carried out in 2007 and 2008 and field experiments were carried out in 2006, 2007, and 2008 with the aim of finding effective herbicide combinations and optimum timing of control. Herbicides containing the active ingredients phenmedipham, desmedipham, ethofumesate, clopyralid, and triflusulfuron were all tested at different timings. Phenmedipham + desmedipham + ethofumesate gave 87% velvetleaf control in pot experiments when applied at the growth stages of velvetleaf cotyledons and one true leaf, but only 27 to 42% control in field trials. Triflusulfuron gave 76% control in pot experiments and 83 to 88% control in field experiments. The timing of the first and second herbicide applications was very important: the first application of herbicides must be at the cotyledon stage of velvetleaf. A 1-wk delay in first application reduced herbicide efficacy by 8%. A 5-d period between the first and second treatments gave 93% control, while a 10-d period between the first and second treatments gave only 77% control. Sugarbeet yield decreased by 60 to 86% due to competition with velvetleaf when a standard herbicide combination (phenmedipham + desmedipham + ethofumesate) was used, and the velvetleaf produced between 6,700 and 14,800 seeds m−2. Inclusion of triflusulfuron in the herbicide treatment significantly reduced velvetleaf seed production to between 200 and 4,700 seeds m−2. In most cases, inclusion of triflusulfuron increased sugarbeet yield. Better velvetleaf control occurred in years when the sugarbeet canopy developed early and the index of leaf area of sugarbeet was higher. Nomenclature: Clopyralid; desmedipham; ethofumesate; phenmedipham; triflusulfuron; velvetleaf, Abutilon theophrasti Medik.; sugarbeet, Beta vulgaris ssp. vulgaris var. altissima L

Effect of a non-woven fabric covering on the residual activity of pendimethalin in lettuce and soil.

BACKGROUND Lettuce (Lactuca sativa L.) is a crop that is very sensitive to herbicide contamination owing to its short growing season. The use of long-residual herbicides and non-woven fabric coverings could therefore influence pendimethalin concentrations in soil and lettuce. RESULTS The pendimethalin half-life in soil ranged between 18 and 85 days and was mainly affected by season (i.e. weather), and especially by soil moisture. Pendimethalin degradation in soil was slowest under dry conditions. A longer pendimethalin half-life was observed under the non-woven fabric treatment, but the effect of varying application rate was not significant. Pendimethalin residue concentrations in lettuce heads were significantly influenced by pendimethalin application rate and by non-woven fabric cover, especially at the lettuces early growth stages. The highest pendimethalin concentration at final harvest was determined in lettuce grown on uncovered plots treated with pendimethalin at an application rate of 1200 g ha-1 (7-38 µg kg-1 ). Depending on growing season duration and weather conditions, pendimethalin concentrations in lettuce grown under non-woven fabric ranged from 0 to 21 µg kg-1 . CONCLUSION Use of transparent non-woven fabric cover with lettuce can help to reduce application rates of soil herbicides and diminish the risk of herbicide contamination in the harvested vegetables.

Effects of adjuvants and carriers on propoxycarbazone and pyroxsulam efficacy on Bromus sterilis in winter wheat

Bromus species are annual winter weeds from the Poaceae family which have become troublesome weeds of winter cereals. The herbicides propoxycarbazone and pyroxsulam are widely used for control of B. sterilis. The objective of this study was to determine the effect of different types of adjuvants and carriers on the efficacy of pyroxsulam and propoxycarbazone on B. sterilis. Small plot field trials were carried out in North Bohemia, Central Europe during 2011–2013. The tested carriers and adjuvants affected the efficacy of both herbicides and the seed production of B. sterilis. Urea ammonium nitrate was a less effective carrier than water (differences 5–30%). The most effective adjuvant was methylated seed oil (MSO), whose addition into the application water solution increased the herbicide efficacy of propoxycarbazone by 5–35%. Efficacy of the herbicide pyroxsulam was increased by adjuvant MSO by 10–30%. Nonionic surfactant increased herbicide efficacy only in 2013 (by 17%). Effect of organosilicone surfactant on the herbicide efficacy was negative (lower efficacy). Seed production of B. sterilis on untreated plots ranged between 20 000 and 50 000 seeds/m2 in experimental years. Seed production was the lowest on plots treated by the herbicide plus MSO (1300–4500 seed/m2).

Environmental and agronomic monitoring of adverse effects due to cultivation of genetically modified herbicide tolerant crops

Herbicide tolerance allows a specific crop variety to survive a herbicide treatment without injury despite the fact that the herbicide cannot be used selectively in a common variety of the same crop. Widely adopted and used worldwide are genetically modified herbicide tolerant (GMHT) crops with tolerance to the non-selective herbicide active ingredients glyphosate and glufosinate. Development of GMHT crops has substantially changed weed control systems and sometimes crop rotations and soil tillage systems. Attention must be given to the environmental and agro-environmental aspects and sustainability of agro-ecosystems based on HT crops because some adverse effects with this technology can appear, especially if used without knowledge of the risks involved and their prevention. This paper identifies main areas that should be monitored and discusses such potential adverse effects as hybridization with related taxa, occurrence of feral crops, and evolved herbicide resistance within weed communities. If there is no principal difference between conventional and GM crop cultivation, we propose monitoring approaches shall be based mainly on existing methods and monitoring networks. Scientific approaches as basis, decentralization with site-specific focus, as well as reasonable extent of data collection and their effective utilization should be the main features of the monitoring.