فهرست مطالب حسین ثابت زنگنه

Plant Protection Organization (PPO) has registered fourteen commercial herbicides formulations for weed control of corn in Iran (Nourbakhsh, 2021). Among these herbicides, eight herbicides contain one active ingredient and the other six have two or three active ingredients including acetolactate synthase (ALS) enzyme inhibiting groups - similar-auxin groups, photosynthetic inhibitors of photosystem II and inhibitors of fatty acids and cell division, which are sometimes formulated with safeners. Weed species do not similarly respond to herbicides and previous studies showed some existing inherent tolerance, causes the percentage control of some of the weed species being lower than the others (Hadizadeh, 2016). Thus, new herbicides with several active ingredients are suggested to be used to suppress such weeds. The aim of this work was to find the best chemical treatments against weeds in corn production based on using new herbicides dicamba+ mesotrione+ nicosulfuron and comparing their efficacy with the common newly or some of older registered herbicides in the major corn growing areas of Iran.

A field study was conducted in four regions of Iran, including Mashhad, Ahwaz, Zarghan and Kermanshah during 2019 growing season. The statistical layout was a completely randomized block design with four replicates. Seven chemical treatments were mesotrione+s-metalachlor+terbuthylazine (Lumax® 537.5SE post-emergence, 4.5 l ha-1), nicosulfuron+rimsulfuron (Ultima® 75%WG, 175 g ha-1), topramezone (Clio® 29.7%SC, 150 ml ha-1), thiencarbazone+isoxaflutol+cyprosulfamide (Adengo® 46.5%Sc, 440 ml ha-1), and the new herbicide dicamba+mesotrione+nicosulfuron with five recommended doses (Calisto Solid 569.5 WG, 400, 500, 600, 700 and 800 g ha-1). A hand-weeded treatment and an unweeded treatment served as controls. Weed density and weed dry weight for each plot were measured four weeks after the last application the herbicides. Corn was harvested from 10 m2 of each plot after removing border plots. Corn grain yield was determined after adjusting the moisture level of grain to 14 %. To measure corn biological yield, samples of 10 corn plants were taken and then were dried in an oven. Data from each region were subjected to statistical analysis using SAS/STAT statistical software and the means were separated by LSD (α=5%).

The results showed a diverse spectrum of weeds (18 species) at the experimental locations. Pigweed species (Amaranthus spp.) were present in all tested locations but were not dominant in Ahwaz. The next dominant weed species were Portulaca oleraceae L. and Chenopodium album L. in Mashhad and Zarghan; Physalis divaricate L. in Ahwaz and Zarghan, Convolvulus arvensis L., Echinochloa crus-galli (L.) P. Beauv., and Corchorus olitorius L. in Ahwaz; Hibiscus trionum L., in Mashhad; Glycyrrhiza glabra L. and Xanthium strumarium L. in Kermanshah and finally Sorghum halepense (L.) Pers., was dominant in Zarghan. Across the experimental locations, dicamba+mesotrione+nicosulfuron was efficient at 700-800 g ha-1 application doses for weed control (75 to 88%). However, when applied at dosage of under 700 gl ha-1, its weed control efficiency was lower (50 to 70%). Topramezone and nicosulfuron+rimsulfuron were inefficient in controlling weeds in all the locations. In contrast, thiencarbazone+isoxaflutol+cyprosulfamide was among the most efficient treatments wich these findings are in agreement with the results of some previous studies (Hadizadeh et al. 2015; Hadizadeh et al., 2020). E. crus-galli was identified as the most difficult-to-control weeds and G. glabra and P. oleraceae were the next ones. None of doses of new herbicide showed injury symptoms on corn.

Dicamba+mesotrione+nicosulfuron (700 and 800 g ha-1) showed 70-85 weed control efficiency averaged in the all experimental locations and it could be recommended to be used in corn field after registration process. Due to environmental concern, it could be applied at lower doses when difficult-to-control weeds were not present. Thiencarbazone+isoxaflutol+cyprosulfamide was found to be the high efficient herbicide. Barnyard grass, licorice and common purslane were difficult-to-control weed species or there were not controlled by new herbicides. We also suggest evaluation of the herbicides for their residual effects on the succeeding crops.

Plant Protection Organization (PPO) has registered 22 commercial herbicides formulations for weed control of wheat, barley and triticale in Iran. Among these herbicides, sixtheen herbicides introduced act as two proposed or only for broadleaved weeds. Their active ingredients including acetolactate synthase (ALS) enzyme inhibiting groups, synthetic-auxin groups,a photosynthetic inhibitor of photosystem II, and pigment synthesis inhibitor groups (Tomlin, 2009). Previous studies show that existing weed species do not similarly respond to herbicides and therefore the percentage control of some of the weed species is lower than the other species (Ohadi, 2010). These hard-to-control weeds are naturally tolerant to herbicides or may be developing resistant to one mode of action. Thus, we need new herbicides to suppress such weeds. The aim of this work was to find the best chemical treatments against weeds in wheat production based on using the new herbicide fluroxypyr and comparing their efficacy with commonly registered herbicides in the major wheat growing areas of Iran.

A field study was conducted in four regions of Iran, including Karaj, Shahryar, Ahwaz, Shiraz, and Gonbad during 2017-2018 growing season. The statistical layout was a completely randomized block design with four replicates. Ten herbicides in 12 treatments were 2,4-D+MCPA (U46-Cambi fluid® 67.5%SL, 1.5 1 L ha-1), Mecoprop-p + Dichloprop-p + MCPA (Duplosan super® 60% SL , 1 L ha-1), Bromoxynil + MCPA (Bromicide® 40% EC, 1.5 L ha-1), Tribenuron-methyl (Granstar® 75% DF, 20 gr ha-1), Mesosulfuron-methyl + Iodosulfuron-methyl sodium+ Diflufenican+Mefenpyre-diethyl (Othello® 75% WG, 1.6 L ha-1), 2,4-D + Dicamba (Dialant super® 46.4 SL, 0.8 L ha-1), Triasulfuron + Dicamba (Lintur® 70% WG, 165 gr ha-1), Bromoxynil + 2,4-D (Buctrile Univeral® 56% EC 1.5 L ha-1), Dichloprop+bentazone (Basagran DP 56.6% SL, 2 L ha-1) and the new herbicide Fluroxypyr with th recommended doses (Kavin Flurox® 20% EC 1.5, 2 and 2.5 L ha-1). An unweeded treatment served as controls. Weed density and weed dry weight for each plot were measured four weeks after the last application the herbicides.  Wheat was harvested from six m2 of each plot after removing border plots. Wheat grain yield was determined after adjusting the moisture level of grain to 14 %. Data from each region were subjected to statistical analysis using SAS/STAT® statistical software and the means were separated by Duncan (α=5%).

The results showed a diverse spectrum of weeds (14 species) at the experimental locations. Descuriania Sophia was dominant in two tested locations Karaj and Shiraz. The next dominant weed species were Galium aparine L., Conringia orientali and Centaurea depressa M.B. were present dominantly in Shiraz. Polygonum aviculare, Fumaria vailantii and Veronica persica were present in Karaj. Lepyrodiclis holosteoides as a noxious weeds, were dominant only in Shahryar. Malva neglecta and Scorpiurus muricatus were in Ahwaz and Bifora testiculata was dominat in Gnbad. Across the experimental locations, fluroxypyr was efficient at 2-2.5 L ha-1 concentrations for weed control (85.77 to 90.68%). However, when applied at dosage of 1.5 L ha-1, total weed control efficiency was lower (80.75%). Bromoxynil + 2,4-D (85.43%) , Dichloprop-p + Bentazon (83.98%) were the most efficient after fluroxypyr. Mecoprop-p + Dichloprop-p + MCPA and Bromoxynil + MCPA with 80% average efficiency controled weeds in all the locations. Triasulfuron + Dicamba and 2,4-D + Dicamba were inefficient in weed control (67.75 and 68.22% , respectively) across all locations. These findings were in agreement with the results of some previous studies (Minbashi and Saeedi, 2019, Minbashi et al. 2020). Lepyrodiclis holosteoides with average control of 63.68% and CV= 23.98% was the most difficult-to-control weed in this experiment. Other weeds beside that were Scorpiurus muricatus, Polygonum aviculare, Malva neglecta and Bifora testiculata identified as difficult-to-control weeds. None of herbicides showed visual injury symptoms on wheat.

According to these experiments, we found that the Fluroxypyr (2-2.5 L ha-1) as new candidate herbicide showed good to excellent (85%-100%) weed control efficiency averaged in the all experimental locations and it could be recommended to be used in wheat field after registration process. Due to environmental concern, it should be applied at lower doses for non-difficult-to-control weeds. We found that Bromoxynil + 2,4-D was the most efficient next herbicide after fluroxypyr and Triasulfuron + Dicamba as an unefficient herbicide overall. L. holosteoides as the most hard-to-control weed was controlled only by upper dose (2.5 L ha-1) of new herbicide. Other difficult-to-control weed species were Scorpiurus muricatus, Polygonum aviculare, Malva neglecta and Bifora testiculata.

One of the negative effects of herbicide residuals is their phytotoxicity on subsequent susceptible crops in rotation. In order to study the phytotoxic residue effects of triasulfuron +dicamba (Lintur® WG70%) on 12 rotational crops, four experiments were carried out at field research stations of Khorasan razavi (Mashhad), Khuzestan (Ahwaz), Fars (Darab) and Golestan (Gonbad-Kavous) provinces in Iran. Rotational crops were planted in sprayed plots (with 170 g Lintur®) or in control plots (without spraying) immediately after wheat harvesting (as second crop) or in autumn. The rotational plants were selected from the summer crops including maize, cotton, mung bean, sesame and soybean, and fall crops including sugar beet, canola, clover, wheat, barley, faba bean and green pea. Results of t-student test showed the significant negative effect of triacsulfuron+dicambba residues on maize at Mashhad, Ahwaz and Darab in terms of root and shoot dry weight and yield (14.6 to 63% yield reduction). Damage to mung bean was significant in Ahwaz and Gonbad (5.6% -29% yield loss). Sesame yield in Ahwaz decreased 46% and soybean and green pea yields in Gonbad decreased by 12% and 16%, respectively. Rapeseed yield was damaged only in Ahwaz (31%) but in Mashhad, Darab and Gonbad the herbicide damage was not significant. Autumn planted sugar beet was significantly damaged in Ahwaz (46% yield) and in Gonbad (5%). The interval between herbicide application and emergence of summer crops was 90-146 days and for autumn crops was 222-311 days, depending on the rotational plants and experimental regions. Herbicide residue of triasulfuron + dicamba did not have significant damage on cotton, clover, wheat, barley and faba beans in related experiments.

Introduction Spinach (Spinacia oleracea) is an annual plant of family Chenopodiaceae. It is cultivated in temperate and cold regions in Khouzestan in autumn and winter. Weeds are the main problems that limit the production of vegetables. Competition ability of spinach against weeds is very low and weeds cause the loss of quality and quantity in this plant. Weeds reduce germination and establishment and growth of spinach. Weed management in spinach should be done at the beginning of the season. Hand weeding is the best way to control weeds spinach, although due to the high cost it is not cost effective, but is steel common in large areas. Weed control spinach, using chemical methods, the number of weeds are kept below the threshold of economic damage.
Materials and Methods The experiment was conducted in a randomized complete block design with 15 treatments and three replications. Treatments included pre-plant application of EPTC at 5 and 6 lit ha-1, pre-plant application of Trifluralin at 2 lit ha-1, pre-plant and pre-emergence application of Pendimethalin at 3 lit ha-1, pre-emergence and post-emergence application of Meteribouzin at 300 g ha-1, pre-emergence and post-emergence application of Meteribouzin at 400 g ha-1, pre-emergence and post-emergence application of Imazethapyr at 0.7 lit ha-1, pre-emergence and post-emergence application of Imazethapyr at 1 lit ha-1, weedy and weed free checks. Each plot the size of 2.5 × 2 meters and 10 row cultivation with distances between rows of 15 cm and the distance between the plants 25 cm and the sowing depth was 3 cm. The herbicide treatments were applied to the back sprayer with Flat fan nozzle with volume of consumption of 240 lit ha-1 solution. The final harvest was about 50 days after emergence. Sampling of weeds 10 days before harvest was performed with using quadrate 0.5 ×0.5.
Results Discussion Important broad-leaf and narrow leaf weeds observed in the field, included field bindweed (Convolvulus arvensis), Common lambsquarters (Chenopodium album), Malva (Malva spp.), Chamomile (Anthemis altissima), Purple nutsedge (Cyperus rotundus), canary grass (Phalaris minor), mouse barley (Hordeum morinum) and Japan brome (Bromus japonicus), respectively. The results of variance analysis showed that the effects of treatments on the number of broadleaf and weed narrow leaves were significant. Meteribouzin and Pendimethalin herbicides (pre-emergence), had better control on broadleaf weed than other herbicides. Low amounts of herbicides EPTC (5 lit ha-1) and imazethapyr (0.7 lit ha-1) were the least effective broadleaf weed control. Trifluralin herbicide reduced approximately 44% broadleaf weed density compared to control plots without control. The minimum weight of broadleaf weed at all doses studied allocated to herbicides Pendimethalin and Meteribouzin. Most of reducing the number narrow leaves was belonged to Meteribouzin and Pendimethalin herbicides as pre-emergence with doses of 300 g and 3 lit ha-1, respectively. The effect of treatments on petiole length, number of leaves per plant and the spinach fresh yield was significant in 1% probability level. Meteribouzin damage in spinach was 100%. It was reported that the half-life in soil herbicide Meteribouzin is about 30-60 days. It seems spinach a high sensitivity to the herbicide and relatively long survival in the soil that causing damage spinach was perfect, while maximum weed control amounts in all methods of used allocated to this herbicide. Number of leaves per plant trait was that less affected by weed interference. Both components of leaves per plant (r= 69.0**) and petiole length (r= 87.0**) showed significant positive correlation with the spinach fresh yield. The highest spinach yield was obtained in Trifluralin herbicide after treatments control. The difference between spinach yield in Trifluralin and control treatments was not significant.
In general, the results showed that the broad and narrow leaf weeds were well controlled by different rates of pre-emergence and post-emergence application of meteribouzin, but this was followed by severe damage in spinach. Trifluralin had the lowest damage effect on spinach leaves. Pre-plant application of trifluralin at 2 lit ha-1 reduced approximately 45% of weed density and increased yield of spinach by 26.6% compared with control treatment. Therefore, this herbicide was recommended to use for weed control in spinach fields. According to the results it seems that the use of herbicide meteribouzin not advisable in spinach whereas causing damage, but due to weed well control is recommended increased resistance spinach to the herbicide through breeding programs. However, it should be noted that spinach leaves are consumed fresh, therefore, investigating the presence of herbicide residues in plant is necessary.