Pesticide Research Journal Vol. 24(1): 55-64, June 2012 Quality Enhancement of Soybean Seed Coated with Nano-formulated Thiamethoxam and its Retention Study Dhruba Jyoti Sarkar, Jitendra Kumar*, NA Shakil and S Walia Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi 110 012, India The use of insecticides for seed treatment is one of the most effective modern pest control practices. Therefore, the influence of these products on the physiological quality of treated seeds should be known. This study aimed to evaluate the physiological quality of thiamethoxam treated soybean seeds stored for three different periods. Seed coating was performed with 12 controlled release (CR) formulations of thiamethoxam based on amphiphilic polymers along with commercial formulation and control. The percent thiamethoxam recovery ranged from 86.1-93.2% from different CR formulation seed coats. Better thiamethoxam retention was observed on soybean seed coats treated with CR formulations. Different seed quality parameters viz., seed germination, seed vigour, seed moisture and seed storability was evaluated during the six month experimentation. The seeds coated with different nano-formulations had better seed quality over control and commercial formulation. Key words: Controlled release, amphiphilic polymers, thiamethoxam, retention, seed germination, seed vigour Seed quality comprises several physical, chemical and biological components. Seed being a biological or living entity, deterioration in its quality with time is inevitable. However, the rate of deterioration could be slowed down either by storing seeds under controlled conditions or by imposing certain treatments with either chemicals or other protectant. As the controlled environment involves huge cost, the seed treatment remains the best alternative approach to maintain seed quality. The most common seed treatments alleviate biotic stress by reducing the damage caused by seed or soil borne pests and pathogens (e.g., insects and fungi) on seeds and seedlings 1-3 . The term “coated seed” has been applied to a seed, which was either pelleted, coated or covered with an adhesive film. Coated seed may, in some circumstances, be produced by a dry powder process, which can have several disadvantages, such as poor adherence, non- uniform application, generation of significant amounts of dust, etc. 4,5 . Seed coating with polymers is one such pre- storage treatment that can be used either singly or in combination with other pesticides as formulation to protect seeds against a pests and diseases. The possibilities of using polymers along with other chemicals to ensure the keeping quality of seeds are reported 6 . The main advantage of this technology includes better adherence of active ingredients, uniform coating and improved seed flow through planter. Coating with a hydrophilic polymer has been reported to regulate the rate of water uptake, reduce imbibitional damage and improve the emergence of soybean seeds 7 . Maize seed coating was performed with temperature responsive polymer to regulate seed germination 8 . The effects of polymer coating on seed vigour in rice have also been reported 9 . In this work, the effect of nano sized controlled release seed coat formulations of thiamethoxam based on amphiphilic polymers is reported on germination percentage, weight, height, moisture content, vigour of soybean. In addition, the tenacity of adherence of thiamethoxam by amphiphilic polymeric formulations on seed coat is reported. MATERIALS AND METHODS Seed coat agents: Amphiphilic nano-polymers were synthesized in our laboratory using different molecular weight PEG (1000, 2000, 4000) as hydrophilic head and aliphatic di-acids and aromatic di-esters namely azelaic acid, sebacic acid, dimethyl terephthalate and dimethyl isophthalate as hydrophobic moiety using conc. H 2 SO 4 as catalyst 10 . The synthesized polymers Poly [poly (oxyethylene-1000)-oxy azelaoyl] (A1), Poly [poly (oxyethylene-2000)-oxy azelaoyl] (A2), Poly [poly (oxyethylene-4000)-oxy azelaoyl] (A-4), Poly [poly (oxyethylene-1000)-oxysebacoyl] (S1), Poly [poly (oxyethylene-2000)-oxysebacoyl] (S2), Poly [poly *Corresponding author E-mail: jitendrakumar7@yahoo.com