THESIS OF PhD DISSERTATION. Vígh Tímea

Transcription

1 THESIS OF PhD DISSERTATION Vígh Tímea Keszthely 2012

2 UNIVERSITY OF PANNONIA GEORGIKON FACULTY, KESZTHELY Institute for Plant Protection Doctoral School of Crop Production and Horticulture Sciences Head of School: Dr. László Kocsis professor Leading Professor: Dr. Gabriella Kazinczi leader EFFECT OF WEED CONTROL TECHNOLOGIES ON HERBICIDE TOLERANT SUNFLOWER HYBRIDS THESIS OF PhD DISSERTATION Written by: TÍMEA VÍGH Keszthely 2012

3 1. Preliminaries and aim of the research work Sunflower represents the most important oilseed plant that is grown in Hungary on the largest area. From a plant protection point of view, its weed control presents a difficult task, where the treatment of sunflower plants against annual and perennial dicotyledonous weeds plays a dominant role. Despite its widely known ability to suppress weed growth, the plant is highly sensitive to weed growth up to the first 4-6 weeks, a plant height of cm. As a result of sunflower breeding over the past several years, new hybrids have been developed and introduced in production, thus an increasing area is assigned these days to the growing of herbicide tolerant sunflower hybrids. A large proportion of producers tends to apply the CLEARFIELD technology along with the application of sunflower hybrids resistant to herbicide substance imazamox, as well as sunflower hybrids resistant to tribenuron-methyl, whose advantage consists in allowing sunflower to be sown in areas where the extent of weed populations prevented the area concerned from being included in sunflower growing. In addition, these hybrids allow for the application of herbicides with a broad spectrum of activity to sunflower plants without the risk of phytotoxicity. Producers need to pay attention only to the level of weed development, with phenological monitoring. The major advantage of both weed control technologies lies in their true efficiency against dicotyledonous weeds a property that used to be missing. In line with the above, the major objective of the thesis has been to compare the weed control technologies applied to sunflower hybrids tolerant to herbicides. In particular, the following issues have been discussed: - comparison of herbicide tolerant and traditional technologies, - assessment of the phytotoxicity of post-emergence herbicides, - specification of whether the applied weed control technologies reduce the amount of sunflower achenes (t/ha), - determination of whether the applied weed control technologies affect the oil content of the sunflower (%), - determination of whether the applied weed control technologies reduce the amount of oil produced by the sunflower (kg/ha), - examination of weed suppression efficiency of various preparations and their combinations.

4 2. Materials and Methods With a view to achieving the goals mentioned above, small plots field trials were performed in three consecutive years, from 2007 to 2009, on the premises of Dow AgroSciences Hungary Ltd. near Szeged. The trials were set up using herbicide tolerant sunflower hybrids applied in cultivation (IMI: NK Meldimi, NK Neoma, Rimisol, and SU: PR63E82). The trials were repeated four times on 6 m plots in length, each consisting of four rows. Each plot had a surface area of 18 m 2. The sunflower fields were contaminated with dicotyledonous weeds. Harvesting was performed using Chanpool (2007) and Wintersteiger Delta ( ) plot combines. Oil content was determined for each plot under laboratory conditions. In experimental years 2007 and 2009, oil yield was specified on the basis of the weed control technologies applied. In the course of assessing phytotoxic effects, the extent of phytotoxicity developing as a result of post-emergence treatments was established visually, in accordance with the ratings provided by BASF, and specified in terms of a single value figure. The effects were recorded 7, 14, and 21 days after post treatments. The chemicals were applied using precision plot sprayers (Pulvirex, Wintersteiger). The herbicides and herbicide combinations used during the trials were assessed on the basis of their effects on the plants and the weeds. Weed surveying was performed using the Balázs- Ujvárosi method. In the course of evaluation, the effects of the trial preparations were assessed only for the absolute control (uncultivated control) and the control subjected only to the post-emergence technology (in the years 2008 and 2009). The efficiency of the treatments compared to the untreated control plants was determined by estimation. Herbicide activity and extent of weed suppression were expressed as a percentage. The results were determined mathematically in accordance with the official EWRS scale. The findings of the trials were then subjected to statistical one- and two-factor analyses of variance, as well as paired t-tests, in order to confirm the reliability of variations in the effects across treatments. The limit of error probability was equal to 5%.

5 2.1. Trials set up in 2007 During 2007, the trials included a control [untreated (weedy) control)] stock of plants, and the exclusively post-emergence application of herbicides in six different (half, normal, 1.5-, 2-, 2.5-, and 3-fold) doses (imazamox and tribenuron-methyl) for sunflower weed control at the 4-6 leaf stage (BBCH 14-16). In the course of the trials, two IMI (Rimisol and NK Meldimi) and one SU (PR63E82) hybrids were used. During harvesting, achene yield (t/ha) was measured and oil content (%) was determined under laboratory conditions. Then the oil yield (kg/ha) was also estimated. Phytotoxicity effects were evaluated 7, 14, and 21 days after treatments (DAT). The effect of herbicides on weeds was assessed twice (two weeks after treatments and before harvesting). The major major weed species on the area included Ambrosia artemisiifolia, Chenopodium album, Convolvulus arvensis, Hibiscus trionum, and Portulaca oleracea. Normal and double doses of post-emergence protoporphyrinogen IX oxidaseinhibitors were applied in Rimisol hybrid using bifenox and flumioxazine as active ingredients, which allowed for a comparison of conventional technologies to herbicide tolerant ones Trials set up in 2008 The hybrids used in 2008 (IMI: Rimisol, NK Meldimi, SU: PR63E82) had already been subjected to pre-emergence treatment (acetochlor + dichlormid, oxyfluorfen, oxyfluorfen + S- metolachlor, flurochloridone, acetochlor + dichlormid + flurochloridone, flurorchloridone+smetolachlor, pendimetalin+dimethenamid, S-metolachlor). At the 4-6 leaf stage of sunflower, herbicides containing imazamox (approved application rate of 45 g of active ingredient per ha) and tribenuron-methyl (approved application rate of 22.5 g of active ingredient per ha) were applied perpendicular to pre-emergence treatments, in single and double doses specified in the authorization document. In addition, the active ingredient tribenuron-methyl was also applied, in line with the typical recommendation, in a split design. In the course of split treatment, the second post-emergence treatment was performed three weeks after the first treatment.. As control, uncultivated, absolute control plants, as well as control plants subjected to post-emergence technology were used.

6 After harvest oil content (%) was determined under laboratory conditions. Phytotoxicity effects were evaluated 7, 14, and 21 DAT: The effect of herbicide treatment on weed suppression was assessed three times, and their efficacy was compared to the untreated control plots (14 days after pre- and 14 days after post treatments, respectively and before harvesting). Dominant weed species included the following: Ambrosia artemisiifolia, Convolvulus arvensis, Chenopodium album, Orobanche cumana, Portulaca oleracea Trials set up in 2009 In the year 2009, the hybrids (IMI: NK Neoma, SU: PR63E82) were subjected to both pre- and post-emergence treatment, which, again, included the most commonly applied technologies (acetochlor + dichlormid, oxyfluorfen, oxyfluorfen + s-metolachlor, flurochloridone, acetochlor + dichlormid + flurochloridone, acetochlor + dichlormid + oxyfluorfen). Similarly to the trial performed in 2008, at the 4-6 leaf stage of sunflower, herbicides containing imazamox (approved application rate of 45 g of active ingredient per ha) and tribenuron-methyl (approved application rate of 22.5 g of active ingredient per ha) were applied perpendicular to pre-emergence treatments, in single and double doses specified in the authorization document. In addition, the active ingredient tribenuron-methyl was also applied, in line with the typical recommendation, in a split design. In the course of split treatment, the second post-emergence treatment was performed 3 weeks after the first spraying.. As control, uncultivated, absolute control plants, as well as control plants subjected to post-emergence technology were used, in addition, plots subjected solely to basic preemergence treatment were included for the sake of comparison. During harvesting, achene yield (t/ha) was measured and oil content (%) was determined under laboratory conditions. The figures obtained were then applied to specify the oil yield (kg/ha). Dominant weed species on arable land in 2009 included the following: Ambrosia artemisiifolia, Convolvulus arvensis, Chenopodium album, Hibiscus trionum. Assessment of weed suppression efficiency was performed at three intervals: on day 14 following pre-emergence treatment, on day 14 following post-emergence treatment, and before harvesting. Phytotoxicity effects were evaluated on 7, 14, and 21 DAT.

7 3. New scientific results 1. Temporary dose-dependent yellow flash developed on IMI hybrids in association with the application of Pulsar 40 SL, a preparation with active ingredient imazamox, which disappeared completely (when applied in the normal dose specified in the authorization document) by the 8-10 leaf stage of the sunflower (approximately two weeks after treatment). Dose-dependent inhibition of growth was also noted later, which appeared to level out by the time of flowering. The intensity of phytotoxic effects appeared to change in line with weather conditions prevailing after application (precipitation, temperature). In case of lower air temperature, phytotoxic effects on sunflower plants persisted over longer periods. Treatment with tribenuron-methyl did not result in an even transitory damage of the SU tolerant sunflower hybrid. Neither discolouration, nor inhibition of growth was recorded. 2. The application of normal and double doses of imazamox and tribenuron-methyl as active ingredients failed to considerably affect average yield, regardless of the basic treatments performed. Various herbicide treatments appeared to affect significantly the achene yield of NK Meldimi. A significant difference wasn t noted, as compared to uncultivated weedy control plots, in the case of NK Neoma and Rimisol hybrids. Normal doses produced no significant differences in case of active ingredient tribenuron-methyl, however, the frequency of application (double dose, split treatment) entailed significant differences compared to uncultivated weedy control plots. 3. Oil content of achenes in the case of imidazolin resistant sunflower hybrids (NK Meldimi, NK Neoma, Rimisol) did not appear to be significantly affected by herbicide treatments, in comparison with uncultivated weedy control plots. Normal and double doses of tribenuron-methyl applied in a split treatment to the SU hybrid (PR63E82) appeared to produce significant differences, compared with the control plants. Following various basic applications, split post-emergence treatments resulted in a significant increase in oil content of achenes.

8 4. Out of imidazolinone tolerant sunflower hybrids, the oil yield of achenes per hectare of NK Neoma and Rimisol hybrids did not appear to be significantly affected by herbicide treatments, as compared to the uncultivated weedy control plants. In the case of NK Meldimi, however, significant increase in oil production was noted when imazamox was applied in half and normal doses. Compared to untreated control, SU hybrid (PR63E82) plots subjected solely to the post-emergence technology showed a significant difference in terms of oil yield in all doses, except the application of normal ones. Following the pre-emergence application of active ingredient tribenuron-methyl in normal doses and the application of normal doses using the split technology, a significant difference compared to weedy control plants was recorded. 5. A statistical analysis of the results obtained allows us to conclude that the above results are largely affected by the genetic characteristics of the hybrids and the weather conditions prevailing in the year concerned. 6. The efficacy of imazamox against weeds largely depends on the weed species, their phenological characteristics, and the dose of the herbicide applied. In provocative trials, the best weed control effect was noted when triple doses of the herbicides were applied. The application of such doses is, however, not recommended in view of the phytotoxic effect on hybrids, and also for economic reasons. 7. The protox inhibitor herbicides alone (bifenox, flumioxazin) applied in traditional technologies, did not ensure satisfactory weed control effect. It is also believed for the application of imazamox and tribenuron-methyl herbicides alone in herbicide tolerant (HT) hybrids. 8. Imazamox and tribenuron-methyl gave good weed control against A. artemisiifolia until max. its 2-4 leaf stage (BBCH 12-14).

9 4. Publications in the subject of the dissertation Scientific papers in Hungarian language: 1. Vígh T. - Kerekes G. - Mészáros G. - Hoffmann R. - Kazinczi G. (2009): Gyomirtási technológiák hatása herbicid toleráns napraforgó hibridekre. Magyar Gyomkutatás és Technológia, 10 (1): Vígh T. - Kerekes G. - Hoffmann R. - Kazinczi G. (2010): Herbicid toleráns napraforgó hibridek kaszattermésének alakulása különböző herbicid kezelések hatására. Acta Agararia Debreceniensis, Agrártudományi Közlemények, Különszám, 2010/39: Scientific papers in foreign language: 3. Vígh T. - Kerekes G. - Hoffmann R. - Kazinczi G. (2012): Comparison of oil-content of IMI- and SU-tolerant sunflower hybrids treated with different herbicides and their efficacy on weeds. Herbologia, 13 : (1): Proceedings in Hungarian language on CD: 4. Vígh T. - Mészáros G. - Kazinczi G. (2008): Gyomirtási technológiák hatása herbicid toleráns napraforgó hibridekre, különös tekintettel a kaszattermés mennyiségi, minőségi alakulására. XIV. Ifjúsági Tudományos Fórum, Keszthely, április 03. CD-kiadvány. 5. Vígh T. - Kerekes G. - Mészáros G. - Kazinczi G. (2009): IMI és SU toleráns napraforgó hibridek gyomirtási eredményei. XV. Ifjúsági Tudományos Fórum, Keszthely, április 16. CD-kiadvány. 6. Vígh T. - Kerekes G. - Mészáros G. - Hoffmann R. - Kazinczi G. (2010): IMI toleráns napraforgó hibrid olajtartalmának, kaszattermésének alakulása különböző herbicid kezelések hatására. XVI. Ifjúsági Tudományos Fórum, Keszthely, március 25. CD-kiadvány.

10 Abstacts in Hungarian language: 7. Vígh T. - Mészáros G. - Kazinczi G. (2008): Gyomirtási technológiák hatása herbicid toleráns napraforgó hibridekre, különös tekintettel a kaszattermés mennyiségi, minőségi alakulására. XVIII. Keszthelyi Növényvédelmi Fórum, Keszthely, január 30. p Vígh T. - Kerekes G. - Mészáros G. - Kazinczi G. (2009): ALS- gátló herbicidekre toleráns napraforgó hibridek gyomirtási eredményei. Dr. Ujvárosi Miklós Gyomismereti Társaság A Gyommentes Környezetért Alapítvány 26. találkozója valamint a Magyar Gyomkutató Társaság Konferenciája, Salgótarján (Salgóbánya) március Magyar Gyomkutatás és Technológia, 10 (1): pp Vígh T. - Kerekes G. - Mészáros G. - Kazinczi G. (2010): Acetolaktát- szintetáz működést gátló herbicidek gyomirtási eredményei herbicid toleráns napraforgó hibrideken. XX. Keszthelyi Növényvédelmi Fórum, Keszthely, január p Vígh T. - Kerekes G. - Mészáros G. - Hoffmann R. - Kazinczi G. (2010): Gyomirtó szerek hatékonyságának vizsgálata IMI és SU napraforgó hibrideken. Dr. Ujvárosi Miklós Gyomismereti Társaság A Gyommentes Környezetért Alapítvány 27. találkozója valamint a Magyar Gyomkutató Társaság Konferenciája, Kaszó, március Magyar Gyomkutatás és Technológia, 11 (1): pp Abstract in foreign language: 11. Vígh T. - Kerekes G. - Mészáros G. - Hoffmann R. - Kazinczi G. (2010): Effect of weed control technologies on herbicide-tolerant sunflower hybrids. 15th International European Weed Reseaech Society Symposium, Kaposvár, July p. 44.