HALT Ambrosia Deliverables

Complex research on methods to halt the Ambrosia invasion in Europe HALT Ambrosia Project ID: 07.0322/2010/586350/SUB/B2 Task ID: D Task Title: Best use of Deliverable ID: DD.2 Date: 01.12.2013

Deliverable Title: Efficacy sheets for bio-herbicides

Responsible partner: JKI, AU Contact person: Dr. Ulrike Sölter ([email protected]) Contributing partners: JKI, AU, Sl Kind of deliverable: X Based on project Desk top study results

Introduction Pelargonic acid and are bio-herbicides which are registered for non-cropping uses in some countries (Germany, Switzerland, USA). The phytotoxic effect of acetic acid was detected over 100 years ago (Fassbender and Grevillius, 1899). Pelargonic acid has been used for some years alone or in combination with and glyphosinate (Arnold et al., 1993). Both acids are found in nature and are broken down rapidly. Pelargonic acid and acetic acid are contact herbicides which cause necrosis on direct contact with plant tissue while uncovered plant part like the root, will stay intact.

Materials and Methods Pot experiments were conducted in Germany, Denmark and Slovenia from April until June 2012. Pelargonic acid and acetic acid were applied simultaneously at two growth stages of ambrosia (BBCH 14-16 and BBCH 22-25) in a spray cabinet (Germany and Denmark) or using a hand-held sprayer (Slovenia). Each bio- was applied at 5 dosages as a single application and as a split application with 50% at the first application and 50% 10 days later. The chosen bio-herbicides are registered for non-cropping uses in Germany: a) Acetic acid (Celaflor: 102g acetic acid/L) b) Pelargonic acid (Rasen MoosFrei: 187.7 g Pelargonic acid/L) The plants were harvested four weeks after the first application. Fresh weight biomass of the above ground Ambrosia plants was recorded.

Statistical analysis was done in SAS (release 9.2). The fresh weight results were subjected to an analysis of variance. Data were subjected to non-linear regression analyses using a log-logistic dose response model:

Efficacy sheets for bio-herbicides 1 HALT Ambrosia Deliverables

D − C Ui = + C (1) 1+ exp[2bi(log(ED50i) − log(z))]

where Ui is the fresh weight, z is the dose, D and C are the upper and lower asymptotes at zero and very high herbicide doses, ED50i is the dose resulting in a 50% reduction in plant biomass, bi is the slope around ED50i and i is the rain treatments.

In equation 1 the ED50 parameter can be replaced by any EDx parameter, e.g. the ED90 parameter that is of more relevance than the ED50 parameter under field conditions:

D − C Ui = + C (2) 1+ exp[2bi(log(ED90i) +1.099 / bi − log(z))]

For each weed species all dose response curves were fitted simultaneously assuming similar D and C parameters. C was not significantly different from zero and a subsequent analysis revealed that the C parameter could be omitted from the model hence equation 2 was reduced to a three-parameter model.

The assumption that logistic dose response curves could be fitted to the data was assessed by a test for lack of fit comparing the residual sum of squares of an analysis of variance and the non-linear regression.

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Results

Table 1. Effects of bio-herbicides on Ambrosia (Germany) Herbicide Growth ED50 ED90 B D Ratio stage (L/ha) (L/ha) Pelargonic acid, single appl. 14-16 49.2 (44.0-54.4) 56.6 (51.8-61.5) -17,0 (-21.6- -12.4) 23.8 (20.0-27.7) 1.0 Pelargonic acid, split appl. 14-16 112.6 (100.9-124.4) 129.8 (118.4-141.1) -17,0 (-21.6- -12.4) 2.3 Pelargonic acid, single appl. 22-25 83.4 (56.5-110.3) 150.4 (111.8-189.3) -4.3 (-6.4- -2.2) 29.1 (24.0-34.1) 2.7 Pelargonic acid, split appl. 22-25 243.8 (109.5-378.1) 439.7 (162.4-717.0) -4.3 (-6.4- -2.2) 7.8

Acetic acid, single appl. 14-16 127.7 (90.0-165.5) 198.1 (158.9-237.3) -5.8 (-8.1- -3.4) 26.0 (17.5-34.6) 1.0 Acetic acid, split appl. 14-16 302.8 (231.2-374.4) 469.6 (383.8-555.4) -5.8 (-8.1- -3.4) 2.3 Acetic acid, single appl. 22-25 196.4 (166.4-226.5) 254.9 (223.1-286.7) -9.7 (-13.6- -5.8) 29.6 (21.9-37.2) 1.3 Acetic acid, split appl. 22-25 347.7 (297.0-398.4) 451.2 (400.2-502.2) -9.7 (-13.6- -5.8) 2.3

Table 2. Effects of bio-herbicides on Ambrosia (Denmark) Herbicide Growth ED50 ED90 B D Ratio stage (L/ha) (L/ha) Pelargonic acid, single appl. 14-16 47.9 (36.7-59.2) 59.4 (47.6-71.1) -11.8 (-16.7- -6.9) 75.9 (56.8-95.1) 1.0 Pelargonic acid, split appl. 14-16 47.6 (36.4-58.7) 58.9 (47.3-70.5) -11.8 (-16.7- -6.9) 1.0 Pelargonic acid, single appl. 22-25 64.8 (45.6-84.1) 93.5 (71.3-115.7) -6.9 (-9.7- -4.2) 134.3 (106.7-161.9) 1.6 Pelargonic acid, split appl. 22-25 66.3 (46.6-86.0) 95.6 (72.9-118.4) -6.9 (-9.7- -4.2) 1.6

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Acetic acid, single appl. 14-16 253.9 (196.4-311.4) 310.5 (251.6-369.4) -12.6 (-18.2- -7.0) 75.9 (56.8-95.1) 1.0 Acetic acid, split appl. 14-16 397.6 (307.5-487.6) 486.2 (394.2-578.2) -12.6 (-18.2- -7.0) 1.6 Acetic acid, single appl. 22-25 199.7 (168.0-231.3) 225.7 (195.4-256.0) -20.7 (-30.2- -11.1) 134.3 (106.7-161.9) 0.7 Acetic acid, split appl. 22-25 523.6 (441.5-605.7) 591.7 (513.4-670.1) -20.7 (-30.2- -11.1) 1.9

Table 3. Effects of bio-herbicides on Ambrosia (Slovenia) It was not possible to estimate the dose-response curves for Pelargonic acid at BBCH 14-16 due to too high efficacy of the applied doses. At BBCH 22- 25 data did not represent the whole dose-response curve. Split applications with Acetic acid applied at BBCH 22-25 had no effect. Herbicide Growth ED50 ED90 B D Ratio stage (L/ha) (L/ha) Pelargonic acid, single appl. 14-16 <33.2 <33.2 - - Pelargonic acid, split appl. 14-16 <33.2 <33.2 - - Pelargonic acid, single appl. 22-25 Ca. 33 >166 - - Pelargonic acid, split appl. 22-25 Ca. 33.2 >166 - -

Acetic acid, single appl. 14-16 116.1 (91.1-141.1) 300.2 (257.6-342.8) -2.7 (-3.1- -2.2) 75.9 (56.8-95.1) 1.0 Acetic acid, split appl. 14-16 108.9 (84.6-133.1) 281.5 (241.1-321.9) -2.7 (-3.1- -2.2) 1.1 Acetic acid, single appl. 22-25 1151.6 (771.1-1532.1) Ca.3000 >7 Acetic acid, split appl. 22-25 >900 >900 - >8

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Pelargonic Acid: Ambrosia fresh matter was efficiently reduced at BBCH 14-16 while the impact on fresh matter was less at BBCH 22-25 in all countries.

Discordant results between the countries were obtained for the single application which performed better than split application in Germany while in Denmark the performance was equal and in Slovenia split application tended to be superior to single application at BBCH 22-25.

For Acetic Acid there were no significant differences in efficacy at BBCH 14-16 and BBCH 22-25 found in Germany and Denmark and single application performed better than split application. In Slovenia a significant higher efficacy was obtained at the youngest growth stage and single application tended to give higher efficacy than split application at BBCH 22-25.

For pelargonic acid the average ED90 dose (required dosage to reduce fresh weight biomass by 90% for Germany and Denmark was ca. 50 L/ha at the early growth stage (BBCH 14-16). For acetic acid the average ED90 dose was 250 L/ha at the early stage and 240 L/ha at BBCH 22-25.

Discussion and Conclusion Results of the experiments in Germany and Denmark are in line with trial results from Verschwele (2006) for single applications showing that pelargonic acid was effective in reducing plant biomass.

Based on ED90 doses in L/ha, pelargonic acid was more active than acetic acid. However for both compounds the ED90 doses were much higher than the ED90 for synthetic herbicides. Ward and Mervosh (2012) found out that Japanese stiltgrass (Microstegium vimineum) treated with acetic acid on an early growth stage was much more effective than on a later growth stage, this could be documented for Ambrosia at the German, Danish and Slovenian site, too. Some results in Slovenia differed from those obtained in Germany and Denmark. For example the efficacy of all applied doses of pelargonic acid at BBCH 14-16 was much higher in Slovenia compared to Denmark and Germany while the efficacy of split applications of acetic acid at BBCH 22-25 was very low. The discrepancies might be related to different climatic conditions and to different application methods resulting in different coverage of plant surface. Overall the results show, that there is a potential for bio-herbicides to control Ambrosia on small scale areas where chemical herbicides and mechanical treatments are not allowed or possible.

References ARNOLD, K.A., A.S. WIDEMANN, R.J. WHITE, M.W. BUGG AND M.N. CLINE (1993): Improved early symptom development with a ready-to-use glyphosate formulation by addition of . Pesticide Science 38, 270-271

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HALT Ambrosia Deliverables

FASSBENDER, G. AND A.Y. GREVILLIUS (1899): Über die Einwirkung von Essigsäuredämpfen und verdünnten Essigsäurelösungen auf Pflanzen. Landwirtschaftliche Versuchsanstalt 52, 195- 208

MALKOMES, H.-P. (2006): Mikrobiologisch –ökotoxikologische Bodenuntersuchungen von zwei zur Unkrautbekämpfung mit hohen Dosierungen eingesetzten Fettsäure-Herbiziden. UWSF Z Mitteilungen der Fachgruppe Umweltchemie und Ökotoxikologie 18 (1) 13-20

Verschwele, A. (2006): Phytotoxische Wirkungen pflanzlicher Öle auf Keimung und Wachstum von Unkräutern. 55. Deutsche Pflanzenschutztagung, Mitteilungen der Biologischen Bundesanstalt für Land- und Forstwirtschaft, 400, 245-246

WARD, J.S. AND T.L. MERVOSH (2012): Nonchemical and Herbicide Treatments for Management of Japanese Stiltgrass (Microstegium vimineum). Invasive Plant Science and Management 5 (1), 9-19

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