DISTRIBUTION OF GLYPHOSATE-RESISTANT GOOSEGRASS (ELEUSINE INDICA) POPULATIONS AND AN ALTERNATIVE HERBICIDE (INDAZIFLAM) TO CONTROL THEM

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1 DISTRIBUTION OF GLYPHOSATE-RESISTANT GOOSEGRASS (ELEUSINE INDICA) POPULATIONS AND AN ALTERNATIVE HERBICIDE (INDAZIFLAM) TO CONTROL THEM Edison Purba 1, Agustinus Purba 2, and Yosephine R. Sianipar 3 1 Faculty of Agriculture, Universitas Sumatera Utara, 2 Alumni Faculty of Agriculture, Universitas Sumatera Utara, 3 PT. Bayer Indonesia Abstract Goosegrass (Eleusine indica) in rubber plantations in Rambutan Estate, PTPN III has been controlled by using glyphosate continuously for 28 years. It has recently been reported that glyphosate is no longer effective for controlling E.indica in the area. How large the area of glyphosate-resistant goosegrass in the Rambutan Estate and what alternative herbicide as control options can be implemented is never reported. This study aims to determine the distribution of E. indica populations that have evolved to be resistant to glyphosate and the possibility of indaziflam as alternative herbicide to control glyphosate-resistant goosegrass population in the Estate. Seed samples from more than 50 plants in each population which had continuously been exposed to glyphosate for 28 years were collected from 14 different rubber plantation blocks. The fourteen putative glyphosate-resistant goosegrass populations were tested for glyphosate resistance along with sensitive population that was never sprayed with herbicides, for comparison, (collected from the Campus Universitas Sumatera Utara in Medan)). Each population is planted as many as 12 plants per pot with three replicates. Plants at 4- to 5- leaf stage were sprayed with glyphosate with a dose of 480 g a.i. per hectare. Each population is arranged in a complete randomized design. The results of spraying goosegrass collected from 14 different populations indicated that eight populations are "highly resistant" and six are "resistant" to glyphosate. Thus, it was concluded that fourteen goosegrass populations at Rambutan Estate have developed resistance to glyphosate. To determine the effectiveness one of indaziflam as alternative herbicide, one population of the goosegrass was applied with indaziflam (PRE) at doses of 50, 75, 100, 150 g a.i per hectare and a plot without control as a comparison. Indaziflam, at all the rates tried, effectively controlled the glyphosate-resistant population. Keywords: Eleusine indica, distribution, glyphosate, goosegrass, resistance INTRODUCTION Herbicide resistance in goosegrass (Eleusine indica) has become a common phenomenon since the first cases of resistance found in oil palm fields in North Sumatra (Purba, 2009, Lubis et al, 2012, Hambali et al, 2015). Today Eleusine indica in more than 10 Estates in North Sumatra have been reported to be no longer controlled by herbicide glyphosate and/or paraquat (Purba, unpublished). In addition, paraquat resistance in E. indica has also been detected in corn fields in Karo District (Ginting et 452

2 Distribution of glyphosate-resistant goosegrass (Eleusine indica) populations and an al, 2015). The number of herbicide resistant populations in North Sumatera, Indonesia is probably more than that of what we have found at the present. Herbicide resistance in weeds will result in weed control failure and therefore affects the crop production and its cost. In modern plantation management weed control is hardly separated from herbicide use. The most common herbicides used in the plantations are paraquat and glyphosate. However, reliance on herbicides with the same mode of action for a long period could lead to the development of resistance (Preston et al, 2009). This study is aimed to determine the distribution of goosegrass resistant to glyphosate at Rambutan Estate PTPN III and the possibility of pre-emergence herbicide, indaziflam as alternative to control glyphosate-resistant goosegrass population. MATERIALS AND METHODS The studies were conducted in field condition at Afdeling Tiga, Kebun Rambutan, PTP Nusantara III, Serdang Bedagai regency, North Sumatera, where glyphosate already failed to control goosegrass. Identification of Glyphosate-Resistant Population Seeds from at least 50 plants each of the putative glyphosateresistant populations of Eleusine indica from fourteen different fields (designated as ESU5.1 to ESU5.14) within the Rambutan Estate, where glyphosate was no longer effective to control after being repeatedly used for 28 years, were collected and transferred to campus of Universitas Sumatera Utara. Plants of each population were grown in pots (twenty plants per pot) with a diameter of 17cm containing mix soil. The plants at 4 to 5-leaf stage, were then sprayed with glyphosate (480 g ai in 400 L water/ha) along with the susceptible population (ESU0) collected from Padang Bulan, Medan that had never received herbicide treatment before. Herbicide was delivered using a semiautomatic knapsack sprayer "Solo. The treatments were arranged in a completely randomized design with four replications. The plants were harvested by cutting them at the soil surface three weeks after application (WAA) and then inserted into envelopes for further drying at 70C for 72 hours. Based on plant survival three weeks after application of glyphosate, the plants were divided into four categories namely highly resistant (survivor 75%), resistant (survivor 453

3 Plant dry weight decrease (%) ESU0 ESU5.1 ESU5.2 ESU5.3 ESU5.4 ESU5.5 ESU5.6 ESU5.7 ESU5.8 ESU5.9 ESU5.10 ESU5.11 ESU5.12 ESU5.13 ESU5.14 Proceedings of International Rubber Conference % - <75%), developing resistance (survivor 2% - <20%) and susceptible ( survival <2%) (Owen and Powles, 2009). Control of Resistant Plant The area used as the research location is a immature rubber plantation (referred to as TBM) planted in 2014 with a spacing of 3.3m x 5m. The experimental area was dominated by four types of weeds including Eleusine indica, Colocoasia esculenta, Axonopus compressus, and Mimosa pudica, each with an SDR value of 41.9% 23.5%, 18.35% and 10.8% respectively. Indaziflam (Becano 500 SC) was applied at five rates (50,75,100,125 and 150 g ai/ha). A manual weeding (scraping soil surface only) and a no weeding plots were also maintained for comparison. Each plot is 30 m in length and 3 m wide along a row of plants. Distance between plots was 4 m. Indaziflam was applied after being diluted with water 400 L. ha -1. The treatments were arranged in a randomized block design (RAK) with four replications. RESULTS AND DISCUSSION Plant survival of the fourteen populations of goosegrass is shown on Table 1. Seven populations have developed high resistance to glyphosate while the remaining is categorized as resistant. Similar results are shown on Figure 1 where the decrease of dry weight of resistant populations was much higher than that of susceptible population (ESU0). In other words, after glyphosate application for 28 years, goosegrass plants have become resistant to glyphosate Population of Eleusine indica Figure 1. The decrease of dry weight of goosegrass (Eleusine indica) plants 3 weeks after spraying with glyphosate 454

4 Distribution of glyphosate-resistant goosegrass (Eleusine indica) populations and an Table 1. Categories of goosegrass populations found in the immature rubber fields at Rambutan Estate. Population Seedsource area ( Block) Dry weight (%) Plant survival (%) Category ESU 0 USU Susceptible ESU Resistant ESU Resistant ESU Resistant ESU Highly Resistant ESU Highly Resistant ESU Highly Resistant ESU Highly Resistant ESU Highly Resistant ESU Resistant ESU Resistant ESU Resistant ESU Highly Resistant ESU Resistant ESU Highly Resistant Table 2 shows that indaziflam at all rates tried reduced dry weight of goosegrass significantly up to 12 weeks after application. Similarly, indaziflam also effectively controlled general weeds in the area (Table 3). In addition, coverage of weeds was still less than 50% even six months after application and therefore no weed control was required for six months after application. Therefore, indaziflam could be used as an alternative herbicide for control of glyphosate-resistant goosegrass populations and other weed species found in the rubber field. Table. 2. Dry weight of Eleusine indica in sample plot (g/0.25m -2 ) 4, 8 and 12 weeks after application with indaziflam (Becano 500 SC) Treatment Rate (g a.i/ha) Dry weight * 4WAA 8 WAA 12 WAA (g/50cm x 50cm) Indaziflam a b b Indaziflam a b b Indaziflam a b b Indaziflam a b b Indaziflam a b b Manual weeding a b b No weed control a a a * Numbers followed by the same letter are not significantly different at 5% based on DMRT. Table 3. Plant dry weight of weeds in sample plot (g./0,25m -2 ) 4, 8 and 12 weeks after application with indaziflam (Becano 500 SC) 455

5 Treatment Proceedings of International Rubber Conference 2017 Rate (ml/ha) Dry weight * 4WAA 8 WAA 12 WAA (g/50cm x 50cm) Indaziflam ab c b Indaziflam ab c b Indaziflam b c b Indaziflam b c b Indaziflam b c b Manual weeding a b b No weed control ab a a *Numbers followed by the same letter are not significantly different at 5% based on DMRT. CONCLUSION In conclusion, goosegrass populations in the fourteen fields of immature rubber where glyphosate had been continuously used for 28 years have developed resistance to glyphosate. Fifty percent of the populations were categorized as highly resistant and the remaining as resistant. The resistant population of goosegrass can be controlled satisfactorily by using indaziflam as an alternative herbicide. ACKNOWLEDGEMENT The author thanks the PTP Nusantara III for allowing the research to be carried out in their rubber field and to Bayer Indonesia for the herbicide sample supply. REFERENCES Ginting, K. A., Purba, E., & Ginting, J. (2015). Identification of weed resistant to paraquat herbicide in corn fields at Tigabinanga Subdistrict Karo District. Jurnal Online Agroekoteknologi, 3(2), Hambali, D., Purba, E., & Kardhinata, E. H. (2015). Dose response of goosegrass (Eleusine indica (L.) Gaertn.) paraquat-resistance biotype to paraquat, diuron, and ametryn. Jurnal Online Agroekoteaknologi. 3(2), Lubis, L. A., Purba, E., & Sipayung, R. (2012). Respons-dosis biotip Eleusine indica resisten-glifosat terhadap glifosat, parakuat, dan glufosinat. Jurnal Online Agroekoteknologi 1(1), Owen, M. J. & Powles, S. B. (2009). Distribution and frequency of herbicide-resistant wild oat (Avena sp.) across the Western Australian grain belt. Crop and Pasture Science, 60,

6 Distribution of glyphosate-resistant goosegrass (Eleusine indica) populations and an Purba, E. (2009). Keanekaragaman Herbisida dalam Pengendalian Gulma, Mengatasi Populasi Gulma Resisten dan Toleran Herbisida. Pidato Pengukuhan Jabatan Guru Besar Tetap Universitas Sumatera Utara, Medan. Preston, C., Wakelin, A. M., Dolman, F. C., Bostaman, Y., & Boutsalis, P. (2009). A decade of glyphosate-resistant Lolium around the world: mechanisms, genes, fitness, and agronomic management. Weed Sci., 57,