FORMULATION OF ETHEPHON BASED LOW-COST YIELD  STIMULANTS FOR COMMERCIAL RUBBER PLANTATIONS IN SRI LANKA 

Ethephon is the only agro-chemical used as the yield stimulant in commercial rubber plantations when practicing low intensity harvesting systems. However, the current reliance on imported ethephon products presents challenges for the industry in terms of cost,  compatibility with local conditions, and availability. This study aimed to develop locally sourced ethephon products and evaluate their effectiveness in Sri Lankan conditions.  After identification of suitable raw materials available in the local market, new water-based  (NWB) and oil-based (NOB) ethephon products have been developed. Xanthan gum was  performed well as the thickener and sulphuric and acetic acids have been selected to maintain the pH of media below 2. Tebuconazole based preservation system has been used to improve the shelf life of the products. Oleic acid was selected to improve slow releasing  properties further in NOB product. With the use of soluble liquid form 48% ethephon, 2.5% water based and oil-based 2.5% products have been developed and tested for the shelf life over a 30 month period. Sustainability of both products have been tested in experimental  scale initially and finally most prominent water based product has been tested in commercial  scale. The results showed that the NWB product did not show significantly different yield compared to the existing products, while the new oil-based (NOB) product achieved significantly higher yields. This suggests the potential for achieving significantly similar yields using a lower concentration of ethephon with the NOB product. Both NWB and  NOB products did not have any adverse effects on latex physiology, flow parameters, or raw rubber properties. Shelf life studies indicated that both products remained stable for 30  months, with no deviations in physical, chemical, or microbiological characteristics. However, the NOB product exhibited phase separation issues after approximately of three months. Cost analysis revealed that the total cost of producing 1 kg of the 2.5% water based and oil-based products were LKR 550.76 and 661.36, respectively, including market prices of ingredients, labour, electricity, packaging, and machinery. Further investigations are required to assess the long-term sustainability of these newly developed ethephon products. 

Keywords: ethephon, low cost, low-intensity harvesting systems, rubber cultivations, water-based product and oil-based product, yield stimulant.