Pest management for preventing of their infestation after flooding : Infestation of weeds and their control

Salvinia cucullata found in Amphure Kamphaeng Saen, Nakorn Pathom Province, Amphure Bang PraMah Supanburi Province, Amphure Bang Sait Ayuthaya Province and Amphure Lard Bua Luang Ayuthaya Province grown naturally in the still water, mixed with other aquatic weeds, with the depth of water 37 to 58 centimeter. The quality of water from different locations were widely difference, the pH was 6.6 to 7.0, hardness was 116-433 ppm, TDS was 189-689 ppm, COD was 16-29 ppm, BOD was 3.8-9.8 ppm, total soluble N was 3.3-6.6 ppm, total soluble P was 3.9-8.8 ppm, total soluble K was 4.5-16.3 ppm. Dry weight and total N and K in Salvinia sp plants from Kamphaeng Saen were higher than in this weed from other locations, while the total K was equal. Growth of Salvinia sp from different locations grown in the same environmental condition were difference. Salvinia sp from Bang Pra Mah and Lard Bua Luang gave highest number of plants. However only the weed from Bang Pra Mah gave highest freshweight. Pumping of the air into the water at 6, 12 and 24 hours a day increased plant growth rate. Fertilizer, 15-15-15 at 10, 20 and 30 ppm and detergent at 5, 10, 20 and 30 ppm did not increased Salvinia sp growth. Salvinia sp plants mixed with P.D. 1 decomposing activator were decomposed at 42 days while water hyacinth plants were deconposed at 60 days. The decompose from Salvinia sp contained more dry weight than water hyacinth while the pH and organic matter content were simliar. However, the water hyacinth contained more P and K than Salvinia sp. 2 and 1.7 times respectively. Herbicides, glyphosate and glufosinate at 1.0 kg ai/ha or 0.25 ppm (the concentration in water where Salvinia sp was grown) and paraquat at 0.75 kg ai/ha or 0.19 ppm provided great control of Salvinia sp. The dried Salvinia sp plants which were affected by herbicides did not sink to the bottom of the cement pots. Glyphosate at 1.0-3.0 ppm, glufosinate at 0.5-2.0 ppm and paraquat at 0.5-2.0 ppm did not reduce fish fresh weight after they were fed for 10 days.