Effect of the herbicide treatment dose on the weed infestation in common winter wheat

Z. Petrova*

Dobrudzha Agricultural Institute, 9520 General Toshevo, Bulgaria
(Manuscript received 10 June 2017; accepted for publication 24 October 2017)

Abstract. The aim of this investigation was to determine the effect of the treatment dose of herbicides on the weed infestation in common winter wheat. The investigations were carried out during 2015 –2016 at Dobrudzha Agricultural Institute (DAI) – General Toshevo. The following herbicides were used: Derby super WG (33 g/ha; 66 g/ha; 132 g/ha), Secator ОD (100 ml/ha; 200 ml/ha; 400 ml/ha), Ergon WG (50 g/ha; 100 g/ha; 200 g/ha), Granstar super 50SG (40 g/ha; 80 g/ha; 160 g/ha), Lintur 70WG (150 g/ha; 300 g/ha; 600 g/ha) and Mustang 306.25 СК (800 ml/ha; 1600 ml/ha; 3200 ml/ha) from the group of sulfunylureas with various mechanism of action. The preparations were applied at three doses – optimal, double and quadruple, at stage 29 (according to Zadoks et al., 1974) of common winter wheat cultivars Dragana, Zlatitsa and Kalina. The herbicide effect was determined by the quantitative weight method and evaluated by the EWRS scale. Regardless of the used dose and the cultivar, Derby super WG, Secator OD, Lintur 70WG and Mustang 306.25СК had highest efficiency (100%) against the following investigated weeds: Sinapis arvensis L., Matricaria chamomilla L., Anthemis arvensis L., Galium tricorne (Stock.), Consolida orientalis (J. Gay) and Cirsium arvensis L. Ergon WG and Granstar super 50SG had 100% efficiency against Sinapis arvensis L., Matricaria chamomilla L. and Anthemis arvensis L. and lower effect (90-94%) on Galium tricorne (Stock), Consolida orientalis (J. Gay) and Cirsium arvensis L.

Achievements and problems in the weed control in grain sorghum (Sorghum Bicolor Moench.)

Gr. Delchev*, M. Georgiev

1Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria (Manuscript received 28 November 2016; accepted for publication 21 March 2017)

Abstract. Chemical control has emerged as the most efficient method of weed control. Herbicides combinations and tank mixtures of herbicides with adjuvants, fertilizers, growth regulators, fungicides, insecticides are more effective than when applied alone on sorghum crops. Their combined use often leads to high synergistic effect on yield. The use of herbicide antidotes for the treatment of seeds in sorghum is a safe way to overcome its high sensitivity to many herbicides. Data regarding herbicide for chemical control of annual graminaceous weeds in sorghum crops are quite scarce even worldwide. Problem is the persistence of some herbicides used in the predecessors on succeeding crops, which is directly related to the weather conditions during their degradation. Most of the information on sorghum relates to the conventional technology for weed control. There is no information about the new Concep technology in grain sorghum. A serious problem is also the volunteers of the Clearfield and Express sun sunflower. They have resistance to herbicides different from that of conventional sunflower hybrids. There is no information yet in scientific literature on control of these volunteers.

Problems and achievements of cotton (Gossypium Hirsutum L.) weeds control

T. Barakova1*, G. Delchev2
1Field Crops Institute, 6200 Chirpan, Bulgaria
2Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 2 June 2017; accepted for publication 17 August 2017) Abstract. Weed control in the cultivation of cotton is critical to the yield and quality of production. The influence of economically important weeds was studied. Chemical control is the most effective method of weed control in cotton but much of the information on it relates to primary weed infestation. Problems with primary weed infestation in cotton have been solved to a significant extent. The question of secondary weed infestation with annual and perennial graminaceous weeds during the period of cotton vegetation is also determined largely by the use of antigraminaceous herbicides. The data related to herbicides to effectively control secondary germinated broadleaf weeds in conventional technology for cotton growing are quite scarce, even globally. We are still seeking effective herbicides for control of these weeds in cotton crops. Studies on their influence on the sowing characteristics of cotton seed and the quality of cotton fiber are still insufficient. In the scientific literature there is not enough information on these questions. The combinations of herbicides, as well as their tank mixtures with fertilizers or plant growth regulators are more efficient than autonomous application. Often during their combined application higher synergistic effect on yield is produced. There is information about cotton cultivars resistant to glyphosate. These cultivars are GMO and they are banned within the European Union, including Bulgaria.

Selectivity and stability of herbicides and their tank mixtures for the seed yield of sunflower (Helianthus Annuus L.)

G. Delchev1*, T. Barakova2

1Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Field Crops Institute, 6200 Chirpan, Bulgaria

(Manuscript received 16 May 2016; accepted for publication 11 August 2016)

Abstract. The research was conducted during 2012 – 2014 on pellic vertisol soil type. Under investigation were 4 sunflower hybrids (Helianthus annuus L.): hybrid Bacardy (an imitolerant hybrid by ClearField plus technology), hybrid Estiva (an imitolerant hybrid by ClearField technology), hybrid Sumico (a tribenuron-methyl tolerant hybrid by ExpessSun technology) and hybrid Arizona (a hybrid by conventional technology). Factor A included the years of investigation. Factor B, herbicides and tank mixtures, included 20 rates. It includes 3 variants by ClearField plus technology, 5 variants by ClearField technology, 5 variants by ExpessSun technology and 7 variants by conventional technology. All variants are on herbicide Gardoprim plus gold 500 SC (S- metolachlor + terbuthylazine) – 3.5 l/ha, which treated after sowing before emergence of the sunflower. It is found that the highest seed yield is obtained at herbicide tank mixture Pulsar plus + Stomp aqua by ClearField plus technology. Tank mixture Listego + Dash + Sharpen by ClearField technology and Express + Trend + Select super by ExpressSun technology also lead to obtaining high seed yields. The most unstable are secondary weed infested checks by the fourth technologies for sunflower growing which are treated with soil-applied herbicide Gardoprim plus gold only. Technologically the most valuable are herbicide combination Pulsar plus + Stomp aqua and herbicide Pulsar by ClearField plus technology, tank mixtures Listego + Dash + Sharpen and Listego + Dash by ClearField technology and Express + Trend + Select super and Express + Lactofol B + Select super by ExpressSun technology. Tank mixtures of herbicides Smerch, Pendigan, Wing, Raft, Pledge and Modown with Amalgerol premium by conventional technology have low estimates due to insufficient control of some weeds in sunflower crops.

Effect of some soil herbicides on vegetative habits of almond trees of ‘Nonpareil’ cultivar grown in a second-year nursery field

Z. Rankova1*, M. Tityanov2

1Fruit Growing Institute, 4004 Plovdiv, 12 Ostromila, Bulgaria 2University of Forestry, 10 Kliment Ohridski, 1756 Sofia, Bulgaria

(Manuscript received 31 May 2016; accepted for publication 26 July 2016)

Abstract. The study was carried out in the period 2010 – 2012 in a nursery field established on the territory of the Fruit-Growing Institute, Plovdiv. The effect of the combined soil-applied herbicide metolachlor + oxyfluorfen (Metofen) and the contact soil herbicide with foliar activity flumioxazine (Pledge 50 WP) on the vegetative habits of ‘Nonpareil’ almond cultivar grafted on almond seedling rootstock was evaluated. In the period 15-25 March, before beginning of vegetation, soil herbicides were applied in the row strip in the second-year nursery field. The following variants were included in the study: 1. Control (untreated, hand- weeded); 2. Metofen – 120 ml/da; 3. Metofen – 240 ml/da; 4. Pledge 50 WP – 8.0 g/da; 5. Pledge 50 WP – 20.0 g/da. The effect of the herbicides on weed infestation and on the vegetative habits of the cultivar/rootstock combination ‘Nonpareil’/almond seedling rootstock was followed up. The results showed that the herbicides applied at the tested rates had a good control on weed infestation and the herbicide activity continued for 3.5-4 months. That makes it possible to eliminate the competitive impact of weeds on the development of the grafted trees for 4-5 months after beginning of vegetation. Visual symptoms of phytotoxicity (chlorosis or necrosis in the leaves and shoots) or an obvious suppression of the development of the grafted trees in the treated variants were not established. A depressing effect on growth of the grafted trees was reported after treatment with Metofen. The contact herbicide with soil and foliar activity Pledge 50 WP – 8.0 g/da can be applied for weed control in a second-year nursery field of almond trees grafted on bitter almond seedling rootstock.

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Selectivity and stability of herbicides and herbicide combinations for the grain yield of maize (Zea Mays L.)

G. Delchev1*, T. Barakova2

1Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Field Crops Institute, 6200 Chirpan, Bulgaria

(Manuscript received 16 May 2016; accepted for publication 9 August 2016)

Abstract. The research was conducted during 2012 – 2014 on pellic vertisol soil type. Under investigation was cycloxydim tolerant maize hybrid Ultrafox duo (Zea mays L.). Factor A included the years of investigation. Factor B included no treated check and 3 soil-applied herbicides – Adengo 465 SC (isoxaflutol + tiencarbazon) – 440 ml/ha, Wing P (pendimethalin + dimethenamid) – 4 l/ha and Lumax 538 SC (S-metolachlor + terbuthylazine + mesotrione) – 4 l/ha. Factor C included no treated check and 5 foliar-applied herbicides – Stellar 210 SL (topramezon + dicamba) – 1 l/ha, Principal plus (nicosulfuron + rimsulfuron + dicamba) – 380 g/ha, Ventum WG (foramsulfuron + iodosulfuron) – 150 g/ha, Monsun active OD (foramsulfuron + tiencarbazon) – 1.5 l/ha and Laudis OD (tembotrione) – 2 l/ha. In addition to these variants by conventional technology for maize growing one variant by Duo system technology is also included in the experiment. It includes soil-applied herbicide Merlin flex 480 SC (isoxaflutole) – 420 g/ha and tank mixture of antigraminaceous herbicide Focus ultra (cycloxydim) – 2 l/ha + antibroadleaved herbicide Kalam (tritosulfuron + dicamba) – 300 g/ha. It is found that herbicide combination of soil-applied herbicide Merlin flex with tank mixture Focus ultra + Kalam by Duo system technology leads to obtaining high grain yield. High yields of maize grain are also obtained by herbicide combinations Lumax + Principal plus, Lumax + Laudis and Wing + Principal plus. The most unstable are the non-treated check and single use of soil- applied herbicides Adengo, Wing and Lumax. Technologically the most valuable are herbicide combination Merlin flex + Focus ultra + Kalam by Duo system technology, followed by combinations of foliar-applied herbicides Principal plus and Laudis with soil-applied herbicides Adengo, Wing and Lumax by conventional technology. Single use of herbicides has low estimate due to must to combine soil-applied with foliar-applied herbicides for full control of weeds in maize crops

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Influence of foliar herbicides treatment on malting barley (Hordeum vulgare L.) productivity of Emon, Vanessa and Vicky varieties

D. Atanasova*, V. Maneva

Institute of Agriculture, 8400 Karnobat, Bulgaria
(Manuscript received 1 July 2016; accepted for publication 26 August 2016)

Abstract. During the period 2012 – 2014 in the Institute of Agriculture, Karnobat a field experiment was conducted with winter malting barley varieties Emon, Vanessa and Vicky. The influence of broadleaf (dicotyledonous) herbicides alone and in their combination with wild oat (monocotyledonous) in tillering stage of the crop was studied in optimal and double doses. The herbicide selectiveness was assessed according to the EWRS scale. Yields were reported after harvest. In variety Vanessa during the treatment with Derby Super, Granstar Super, Sekator OD and combination of Puma Super 7.5 EW + Sekator OD in optimal doses, the yield does not differ from the weed control. Variety Vicky endures well the treatment with optimal doses in all of the tested herbicides, except Husar Max. In treatment with double doses, only Granstar Super does not affect negatively the yield of grain. Comparing the data from ANOVA about the role of herbicides and year conditions on the malting barley varieties it can be concluded that the yield of variety Emon is the most stable in regard to herbicides applied in optimal doses (5%), followed by Vanessa (17%) and Vicky (18%). At application of the herbicides in double doses, their influence is increased – in variety Emon up to 15%, and in varieties Vanessa and Vicky – up to 23%.

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Effect of some herbicides on weeds and vines in mother plantation of Cabernet sauvignon

N. Prodanova – Marinova*

Institute of Viticulture and Enology, 5800 Pleven, Bulgaria
(Manuscript received 1630 May 2016; accepted for publication 17 August 2016)

Abstract. To maintain soil surface clean of weeds in the parent vineyard for producing cuttings for scions, the efficiency and selectivity of Gardoprim plus Gold (312.5 g/l s-metolachlor + 187.5 g/l terbuthylazine), Wing P (pendimethalin 250 g/l + dimethenamid P 212.5 g/l) and Lumax 538 SC (375 g/l s-metolachlor + 125 g/l terbuthylazine + 337.5 g/l mesotrione) at doses of 0.4 and 0.6 l/da was studied. Lumax 538 SC, Wing P and Gardoprim Plus Gold controlling efficiently annual weeds established in parent vineyard, except Xanthium strumarium L.. Lumax 538 SC and Gardoprim plus Gold showed long-term (90 days) activity. Wing P activity decreases after the thirtieth day. The tested herbicides do not damage the buds and do not lead to a reduction of shoots developed from them. Lumax 538 SC and Gardoprim plus Gold at doses of 0.4 and 0.6 l/da and Wing P at dose of 0.4 l/da do not inhibit the growth of shoots. The largest number of cuttings for scions were obtained after treatment with Lumax 538 SC.

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Selectivity and stability of new herbicides and herbicide combinations for the seed yields of some field crops

G. Delchev*

Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 28 January 2016; accepted for publication 30 May 2016)

Abstract. During 2013 – 2015 on pellic vertisol soil type was conducted a field experiment. Under investigation was Bulgarian milk thistle cultivar Silmar (Silybum marianum Gaertn.). Factor A included the years of investigation. Factor B included no treated check, 6 soil-applied herbicides – Tendar EC, Sharpen 33 EC, Merlin flex 480 SC, Smerch 24 ЕC, Raft 400 SC, Eagle 75 DF and 5 foliar-applied herbicides – Kalin flo, Eclipse 70 DWG, Sultan 500 SC, Granstar super 50 SG, Starane 250 EK. Factor C included no treated check and 1 antigraminaceous herbicide – Tiger platinium 5 EC. All herbicides, herbicide combinations and herbicide tank-mixtures were applied in a working solution of 200 l/ha. Mixing of foliar-applied herbicides was done in the tank on the sprayer. Soil-applied herbicides were treated during the period after sowing before emergence. Foliar-applied herbicides were treated during rosette stage of the milk thistle. Tank mixtures of antigraminaceous herbicide Tiger platinum with foliar herbicides Kalin flo, Eclipse, Sultan, Granstar super and Starane leads to obtaining high seed yields of milk thistle. High yields seeds are also obtained by foliar treatment with Tiger platinum after soil-applied herbicides Raft, Sharpen and Eagle. The use of the soil-applied herbicides Smerch, Merlin flex and Tendar does not increase the seed yield due to its higher phytotoxicity against milk thistle. Herbicide Tendar and herbicide combination Tendar + Tiger platinum are the most unstable, followed by herbicide Merlin flex. Herbicide tank-mixtures Kalin flo + Tiger platinum and Eclipse + Tiger platinum and herbicide combination Raft + Tiger platinum are technologically the most valuable. They combine high seed yield with high stability with relation to different years. Single application of soil-applied or foliar-applied herbicides have low estimate; due to that they must be combined for full control of weeds in milk thistle crops.

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Selectivity and stability of vegetation-applied herbicides in cotton (Gossypium hirsutum L.)

T. Barakova1*, G. Delchev2

1Field Crops Institute, 6200 Chirpan, Bulgaria
2Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 16 May 2016; accepted for publication 26 May 2016)

Abstract. An experiment was carried out during 2013 – 2015 in the experimental field of the Field Crops Institute, Chirpan, with two cotton cultivars − Helius and Darmi (Gossypium hirsutum L.). Herbicides: Goal 2 E, oxyfluorfen (80 ml/da); Linuron 45 SC, linuron (200 ml/da); Wing-P, pendimethalin + dimethenamid (400 ml/da); Merlin 750 WG, isoxaflutol (5 g/da); Bazagran 480 SL, bentazone (150 ml/da) were investigated. They were treated separately or combined with growth regulator Amalgerol (500 ml/da) or foliar fertilizer Lactofol O (500 ml/da) in the budding stage of the cotton. It was established that selectivity is the lowest in the two cotton cultivars with herbicides Linuron 45 CK and Merlin 750 WG. The purpose of this investigation was to establish the selectivity and stability of some herbicides and their tank mixtures on the cotton by influence of different meteorological conditions. It has been found that the highest phytotoxicity on cotton is given the vegetation-applied herbicides Merlin and Linuron. Foliar fertilizer Laktofol O reduces phytotoxicity of herbicides Goal, Wing, Merlin and Bazagran in two cotton cultivars. Herbicides Wing and Bazagran have excellent selectivity for the two cotton cultivars – Helius and Darmi. The highest yield was obtained by vegetation treatment with herbicide Bazagran, followed by herbicides Wing and Goal. Tank mixtures of Goal, Bazagran and Wing with Laktofol, followed by those with Amalgerol are technologically the most valuable. They combine high yield with high stability over the years. Аlone application of herbicides Linuron and Merlin and their tank mixtures with Amalgerol and Laktofol have low estimate.

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