Thesis (M.Sc.) - Asian Institute of Technology, 2003

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science. Inter-University Program on Environmental Toxicology, Technology and Management.

Cypermehrin is a synthetic pyrithroid used to control a variety of pest. As the natural pyrithroid is readily degradable in the natural condition with known to environmental friendly, the synthetic pyrithroid was introduced in to the market. A commercial cypermethrin product containing (RS) - oc -cyano-3 - phenoxybenzyl (lRs, 3RS; IRS, 3RS) - 3 (2, 2-dichlorovinyl) -2, 2-dimethylcyclopropanecarboxylate having effective concentration 25% w/v, was obtained from a local market and had been used through out the study. The experiment was designed in a randomize complete block design (RCBD) consisting of four blocks (Block I, Block II, Block II, & Block IV) and three replicates (T1, T2, & T3) under each block. The soil of the experimental plot has its pH is slightly acidic (5-6.5), soil organic carbon is high (4%) and the soil type is clay (60% clay content). In this experiment, three concentrations of pesticide were applied. In treatment 1 (T1) no pesticide was applied, so the active compound applied was 0 gm /ha; and for treatment 2 (T 2) and treatment 3 (T 3) the dose was 10 gm/ha and 30 gm/ha respectively. T 1 and T2 were covered by plastic at the surrounding of the plot at all times, and on the top during the application of pesticide in this and surrounding fields but T 3 was uncovered all the time. The experiment was conducted in rainy season and there was also an option to watering the vegetables twice a day from the shallow cannel surrounded. Both the soil and vegetable were collected according to the schedule and tested in the laboratory. Dose dependent yield and maximum residual limit in the Chinese kale was found in the study. The amount of cype1methrin found in the soil samples were directly correlated with the doses applied. In this experiment, it was found that water has no potential effect in removing the pesticide residue from the Chinese kale plants. The degradation time needed to be degraded 50% of the compound (DT50) was found from 4 to 5 days and DT90 was found from 17-19 days. A filter paper acute toxicity test using earthworms as the test organism was also conducted in the laboratory condition with the local Thai earthwo1ms and the median lethal concentration that kills 50% of the organism (LC50) was found at 1.03 mg/cm2 , LOEL was observed at 0.001 mg/ cm2 and the NOEL was observed at 0.0001 mg/cm2 of the filter paper.