Management of Port Mourant vine (Phaseolus schotti) at Albion/Port Mourant Estate, Guyana. N. Seepersaud and D. P. Bishundial

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1 Management of Port Mourant vine (Phaseolus schotti) at Albion/Port Mourant Estate, Guyana. N. Seepersaud and D. P. Bishundial Guyana Sugar Corporation Inc., Guyana Abstract Phaseolus schotti (Benth), known as Port Mourant vine, is one of the most troublesome broadleaf weeds in the sugarcane fields in Guyana. Since its discovery on the Estate in the early 1970 s, the weed has increased its population steadily to such a state that its management has become very challenging. The weed is known to emerge late in the crop cycle, which leads to tremendous problems at the time of harvesting. As a result, exorbitant sums are paid to encourage harvesters to cut canes where the weeds are present and infestation considered heavy (>30.0%). Several broad-leaf herbicides were used over the past years, but control was only short-term. With the introduction of Starane (Fluroxypyr), and the continued use of 2, 4 - D Amine, effective control is achieved for this weed in the crucial stages of growth of the sugar cane crop. This method, along with manual control, offers sustainable control of this troublesome weed. Management strategies developed over the years to reduce the spread and infestation levels of this weed, are discussed. Key words: Phaseolus schotti, Strategies, Starane, 2, 4 - D Amine. Introduction Phaseolus schotti or Port Mourant vine is an annual legume from the Fabaceae family that is propagated by seed. The seeds are protected by a hard seed coat, which prevent air and water absorption (Salisbury and Ross, 1989). Such characteristics are common for most species of the Fabaceac family thus exemplifying the long dormancy period it exhibits. The seeds are borne in pods, which are produced in pairs. Each pod contains 5 to 20 seeds and each plant produces pods. The flowers are 2-3 cm wide and are loosely arranged, very bright and deep yellow in colour. Port Mourant vine is a common weed in the sugarcane fields, especially on dam-beds and on dams close to waterways. It is referred to as a shade plant due to the fact that it germinates and grows vigorously even after canopy has been established. After germination, the weed supports itself on the nearby sugarcane crop by producing tendrils that wrap the cane stalks, enabling it to climb to the top for sunlight. Upon reaching the top, new branches are produced that can smother a surface area of

2 approximately 60m 2 per plant. This restricts sunlight the cane crop needs for photosynthesis. The weed was discovered at the Albion/Port Mourant Estate over three decades ago and its population has increased significantly over the years. High expenditures are incurred to control its population and as payment for obstacles at the time of manual harvesting (Table 1). Control measures include the application of herbicides and manual control methods. However, these have tended to be short-term and the weed has been able to further manifest itself to the extent that its management has become very challenging and the cost of controlling it always escalated. In the year 2003, management strategies were set up to reduce the infestation of Port Mourant vine at Albion/Port Estate to a more manageable one and prevent further reinfestation. These strategies and the results are discussed. Previous control methods Medium to late post emergence stages were targeted with 2, 4-D Amine or Starane (Fluroxypyr) when canes were three months old and younger. At least one round was done. Hand weeding was practised in canes 4-7 months old when the weed density was considered heavy. Roguing was practised on a small scale where the density was slight and cane age permitted easy traversing. Methods Cultural control In the maintenance of the aquatic system, emphasis was placed on weeding one metre along the edges of the canals to avoid the seeds of Port Mourant vine from getting into the water-way from where it can be transported into the field. This water is also used for irrigation purposes. Known endemic areas were replanted at closer inter-row spacing (1.2m - 1.4m) instead of the routine 1.5m to enhance early canopying and reduce on available sunlight for germination and growth. Flood fallow practices increased significantly during the year. 33 % of the total planted area for the year was on flood-fallowed lands. Flood fallowing is the total submergence of the land with at least 30 cm of water above the highest point in the field for a minimum of six months after tillage is completed. 2

3 Mechanical control Mechanical dam maintenance (slashing) was practised more frequently, which supressed the weed at critical growth stages. This was practised when the weeds were at medium to late post stage but before podding starts, which prevented the weed from producing new seeds to increase its population. Chemical control 2, 4-D Amine was applied to the weed when it was at an early to medium post stage (15-30 cm high). Frequent post application inspections were made and repeated treatments of 2, 4-D Amine was administered either as a broadcast or target treatment as was deemed necessary. Non-cropped areas where Port Mourant vines were found growing were sprayed with Glyphosate [Touchdown (2.7L/Hectare) or Round Up (2.4 L/Hectare)]. 2, 4-D was incorporated in the chemical ripener and applied at a rate of 1.4 L/ hectares. The chemical ripener was Touchdown (705 ml/ha). This was done on a known Port Mourant vine endemic area (Ankerville EW 1-11) seven weeks prior to harvesting. Port Mourant Vines on dam-beds were targeted with 2, 4-D Amine using a boat that transversed in the canals. Manual control Manual control was done in two ways. 1. Hand weeding was encouraged when the weed density was moderate to heavy in the fields. Here the weeders would cut the vines at base levels (close to the ground) and at the same time stripping some of the vines from the canes. This relieved the canes of the smothering vines and exposed the leaves to the sunlight that aided photosynthesis. This practice was done when the canes were four months and older. 2. Roguing was practised in fields where the canes were much younger and when the vines were at slight densities. Here the persons would transverse the fields and uproot all the germinated weeds and place them between the rows. Rougeing is considered more tedious than hand weeding but is more effective due to the fact the weeded vines tend to produce new branches just below the uncut portion on the ground. These may later grow to create problems at the time of manual harvesting. 3

4 Results Infestation levels at the end of the year 2003 indicated that an impact has been made in reducing the population of the Port Mourant vine. The total area of infestation did not change considerably but the infestation densities have reduced Table 2. Cultural control was very successful. Prepared fields submerged with water for six months before planting gave effective control of Port Mourant vine. Obstacle cost of the end of March 2004 was US $ at a CPU of US $ 0.05 compared to US $ for the corresponding period in year 2003 at a CPU of US $ By the end of year 2003, obstacle and weed control cost reduced by 18% compared to the previous year (2002) and 53 % compared to year 2001 Table 1. The reduced inter row spacing apparently restricted the germination of the weed. No cost for obstacle was paid for at an area previously known as an endemic area (Resource OG 17-28). Non-cropped areas (dams) are now almost Port Mourant vine free, 2, 4-D Amine applied at the time of chemical ripener was not successful. The leaves of the vines appeared dry but after burning stems remained unburnt and entangled on the canes. Boat spraying reduced the population on dambeds significantly from approximately 45 % at the beginning of the year to approximately 20 % at the end of the year for the entire cultivation. Very good control was achieved from the chemical control done but due to the prolong dormancy period the seeds exhibited, germination continued at different times during the crop cycle. In most cases, two and three rounds of 2, 4-D Amine application were done to restrict the infestation and prevent further re-infestation. 4

5 Conclusions The experiences with Port Mourant vine over the past years have shown that the weed is a very aggressive and troublesome one. Chemical and manual control employed in the past were not wholly successful. The introduction of Starane and continued use of 2, 4 - D Amine and manual control in the cropped areas and mechanical control in the non-cropped areas have reduced the population on Albion/Port Mourant Estate cultivation significantly. Non-cropped areas should continue to be targeted with non-selective herbicides and mechanical control methods. Manual and selective herbicides controls proved to be very effective in reducing the infestation levels to a more manageable state in the cropped areas. However, the infestation levels still proved a tedious task ahead but all efforts and resources are pooled to make it an achievable one. More efforts need to be made in evaluating the effects of applying agrochemicals on cane between four to eight months old. While eradication of Port Mourant vine from the Albion/Port Mourant Estate is a long-term possibility, reliable strategies to manage the weed have been put in place. The successful use of chemical, manual and mechanical control will guarantee effective control of the current infestation and reduced reinfestation. The increase in flood fallow practices will assist greatly in realizing this. Table 1 Costs for weed control and obstacles for the past five years ( ). CHEMICAL MANUAL OBSTACLES TOTAL Year US $ US $ US $ US $ , , , , , , , , , , , , , , , , , , , ,000 5

6 Table 2 Infestation levels of Port Mourant Vine at the beginning and end of Year Beginning of 2003 End of 2003 Density Area (Ha) % Of Cultivation Area (Ha) % Of Cultivation Slight ( 20 %) Moderate (21-30%) Heavy (> 30%) Total Acknowledgements We would like to thank Mr Aaron Dukhia and Mr Sahadat Baksh, General and Agriculture Managers resp.of EBE Estates for their initiative and support in this project. We are also grateful to Mr Peter Persaud and Jalil Ahmad for theinformation provided for this paper. References Persaud, P. and Bishundial, D. P. (1997) Management of Port Mourant Vine at Albion/Port Mourant Estate. Internal Circulation, Albion Estate, Guyana Sugar Corporation Ltd. Ahamad, J. (1998). Phaseolus scotti: Biology and Chemical Control. Final Year Project, University of Guyana. Seepersaud, N (2003). Management Approach to Control Port Mourant Vine, Internal Circulation, Albion Estate, Guyana Sugar Corporation Ltd. Salisbury, F.W and Ross, E. W (1998): Plant Physiology. 3 rd Edition. Wadsworth Publishing Co. California, U. S. A. GSES Annual Report (1982). Internal Publication. Guyana Sugar Corporation Ltd. GARU Annual Report ). Internal Publication. Guyana Sugar Corporation Ltd. 6