Jursík M., Soukup J., Holec J., Andr J., Hamouzová K. (2015): Efficacy and selectivity of pre-emergent sunflower herbicides under different soil moisture conditions. Plant Protect. Sci., 51: 214-222.We ranked the most frequently used pre-emergent herbicides in sunflower (Helianthus annuus) according to their efficacy and selectivity under different soil moisture conditions within 2008-2011. The efficacy of oxyfluorfen, aclonifen, acetochlor, dimethenamid, and propisochlor on the majority of weeds (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 acetochlor. For flurochloridone, the phytotoxicity increased due to irrigation after herbicide application. The highest sunflower injury rate (27-35%) was recorded after application of oxyfluorfen.

Four efficacy and selectivity small plot field trials were carried out in four sunflower hybrids at two localities in Middle Bohemia during 2008 and 2009 with herbicides containing the active ingredients flumioxazin and fluorochloridone. For Chenopodium album, an efficacy of 97% was found after pre-emergent application of fluorochloridone + acetochlor; the efficacy of oxyfluorfen was 88-95%; the efficacy of flumioxazin was below 50% at both tested application rates (30 and 60 g/ha) and application timings (2 sunflower leaves and 4 to 6 sunflower leaves); efficacy of flumioxazin increased to 67% and 69%, when surfactants were added (isodecyl alcohol ethoxylate and heptamethyltrisiloxan). Full control of Amaranthus retroflexus was found after all pre-emergent and early post-emergent herbicide treatments; efficacy of late post-emergent herbicide treatments was below 93%. Full control of Mercurialis annua was found only after application of oxyfluorfen. Thlaspi arvense was fully controlled by fluorochloridone + acetochlor (pre-emergent) and oxyfluorfen (in both application terms). Selectivity of the four tested sunflower hybrids to fluorochloridone + acetochlor, bifenox and flumioxazin was acceptable (phytotoxicity 6 to 27%). Higher phytotoxicity (23-45%) was recorded when surfactants were added to flumioxazin. The highest phytotoxicity (68-81%) was recorded after the application of oxyfluorfen.

Production of maize (Zea mays) is increasing globally and this trend is evident throughout the Central Europe. We may expect this trend to continue in the future (Tatsumi et al. 2011). At the present time, maize is the most significant crop in the world. Weed management had a major affect on the success of maize growth, because the competition ability of maize is relative low.The critical weed-free period for maize is between the 3 rd and the 6 th weeks after emergence (Zimdahl 2004). Weed competition is manifested by a decrease of maize biomass and yield losses, which is usually between 30% and 50%, depending on the weed density, time and duration of competition, weed spectrum and other factors (Hurle 1988 ABSTRACTThe aim of this work was to compare herbicide efficacy and reduction of weed reproduction after the application of three frequently used soil residual herbicides during pre-emergent (PRE) and early post-emergent (EPOST) application in maize. Plot field trials were carried out in Central Bohemia during two growing seasons (2010 and 2011). Good efficacy (88%, resp. 83%) was found in isoxaflutole + thiencarbazone (ISF + THC) and terbuthylazin + S-metolachlor (TBA + SMC) on Echinochloa crus-galli, especially in PRE application use. Efficacy on Amaranthus retroflexus was 91% at both tested application periods and there were no significant differences between experimental years. Significant differences in A. retroflexus control were recorded among all tested herbicides (ISF + THC > TBA + SMC > pendimethalin (PEM) + dimethenamid (DMA)). No significant differences between PRE and EPOST were recorded in efficacy on Chenopodium album. Significant differences in efficacy on C. album were recorded among all tested herbicides (ISF + THC > TBA + SMC > PEM + DMA). Mercurialis annua was the most tolerant tested weed, which was significantly better controlled at EPOST herbicide application (73%) compared to PRE application (32%). TBA + SMC showed a significantly higher efficacy on M. annua compared with other tested herbicides. Seed production of all tested weeds was strongly effected by weather conditions, which were significant during 2011, when there was higher than average precipitation during May and June. The most seeds were produced by A. retroflexus > C. album > E. crus-galli > M. annua. ISF + THC best reduced seed production of E. crusgalli, A. retroflexus and C. album, especially when applied at PRE. TBA + SMC best reduced seed production of M. annua. Weed competition on untreated control plots caused yield loss by 90%and 47% in 2011 and 2012, respectively, compared to treatments with the highest yield (ISF + THC).

The aim of this work was to compare the efficacy, selectivity to sunflower and dissipation of three pre-emergent herbicides. Flurochloridone, linuron and oxyfluorfen were applied individually and each herbicide was also applied in a tank mix with two different adjuvants (a silicon-based adjuvant and paraffin oil). Small-plot field trials were carried out with sunflower in Central Bohemia in 2012 and 2015. Around 25–35% of the active ingredients in the applied herbicides were detected in soil 60 days after application in both years, except for oxyfluorfen in 2012, whose residual concentration was 60%. The tested soil adjuvants did not affect the dissipation of any of the tested herbicide in soil in either experimental year. Oxyfluorfen exhibited the highest mobility and caused the greatest degree of sunflower injury (18%), especially in the year with high rainfall shortly after application. None of the tested adjuvants significantly affected sunflower injury by any tested herbicide. The efficacy of flurochloridone and linuron on Fallopia convolvulus was strongly affected by weather conditions shortly after application. The efficacy of oxyfluorfen was around 85% and was not affected by weather conditions. The effect of adjuvant on herbicide efficacy was positive only in dry conditions, where the efficacy of flurochloridone on F. convolvulus was positively affected by the silicon-based adjuvant.

Jursík M., Fendrychová V., Kolářová M., Andr J., Soukup J. (2017): Optimising Clearfield and ExpressSun sunflower technologies for Central European conditions. Plant Protect. Sci., 53: 265-272.The efficacy and selectivity of herbicides and tank-mix combinations at different application terms in Clearfield and ExpressSun sunflowers were evaluated. Five-plot field trials (2011)(2012)(2013)(2014)(2015) were carried out in Prague. The efficacy of tribenuron (TBM) was excellent and quite rapid on chenopodium album. Its efficacy on other tested dicot weeds ranged around 90%, depending on weather conditions and growth stages of weeds. echinochloa crus-galli was not controlled by TBM. The tank-mix combination of TBM + propaquizafop (PQF) caused sunflower injury when applied in a very cold growing period. Under dry conditions, PQF efficacy on e. crus-galli was strongly reduced. The split application of TBM, when PQF was used at the second application, was less negatively affected by herbicide antagonisms. Very good results were obtained on plots with pre-emergence treatment with dimethenamid and post-emergence with TBM. The efficacy of imazamox (IZM) on dicot weeds was strongly affected by growth stages of weed and weather conditions during application. Efficacy of IZM on e. crus-galli was increased by oil adjuvant, but this adjuvant reduced IZM selectivity. The best efficacy, selectivity, and Clearfield sunflower yield were on plots with the split application of IZM.

The aim of this work is to describe the differences in sensitivity of Clearfield, ExpressSun and non-herbicide tolerant (HT) sunflower cultivars to several acetolactate synthase inhibitor herbicides and to find out the differences in sensitivity in F1 and F2 generations of these cultivars. Non-HT sunflower was very sensitive to most of the tested herbicides, except for nicosulfuron (efficacy 43-75%). F2 generation of non-HT sunflower showed a low level of sensitivity to imazamox (efficacy 10-43%) and to nicosulfuron, tribenuron, thifensulfuron and rimsulfuron under dry conditions (efficacy 43-83%). Sensitivity of Clearfield sunflower (cultivar with tolerance to imidazolinone herbicides) to tested sulfonylurea varied according to used herbicide and weather conditions. The highest efficacy on Clearfield sunflower showed iodosulfuron (97-100%) > florasulam (88-100%) > foramsulfuron (40-98%) > thifensulfuron (12-99%) > rimsulfuron (37-99%) > tribenuron (0-87%) > nicosulfuron (0-78%). ExpressSun sunflower (cultivar with tolerance to tribenuron) was the most tolerant to all tested herbicides. The lowest efficacy on F1 generation showed tribenuron (0%) > imazamox (0-17%) > nicosulfuron (0-43%) > thifensulfuron (0-57%) > rimsulfuron (0-70%) > foramsulfuron (8-75%) > florasulam (75-96%) > iodosulfuron (87-98%). Sensitivity of F2 generation of ExpressSun to tested herbicide was usually higher as compared to F1 generation.

The aim of this work was to verify and assess the tolerance of the PR63E82 (ExpressSun) sunflower cultivar to tribenuron, propaquizafop and their tank-mix combination in two rates under various weather conditions. Three small-plot field trials were carried out on sunflower in Prague, Czech Republic, from 2015 to 2017. High phytotoxicity (25–56%) of tribenuron (TBM) + non-ionic surfactant was observed in 2015 and 2016 when the sunflower was sown in mid-April. In 2017, phytotoxicity was significantly lower (4–6%), probably due to a later sowing of sunflower (May), and hence higher temperatures. The main symptoms of TBM phytotoxicity were leaf chlorosis, necrosis and growth retardation. Propaquizafop (PQF) injury was minimal in 2015 and 2017. A higher phytotoxicity (10–13%) was recorded in 2016, probably due to a hail which occurred 2 days after T2 (second application term (sunflower BBCH 14)) application. Plant injury had puckered leaves and also made more side branches. TBM + PQF damaged sunflower plants most of the tested herbicide treatments (phytotoxicity 3–62%). High phytotoxicity caused stem branching, increased number of sunflower heads and decreased yield.