Screening For Plant Extracts Synergistic To Dimefluthrin In Repellent Incense

Botanical pesticides have many advantages, such as high selectivity, low toxicity, easy to degradation, unease to form resistance for pest, etc, which cannot be substituted by chemical synthetic pesticides. As for mosquito control which has closed relationship to people'life, botanical pesticides are less poisonous to human beings and more environmentally friendly. So to decrease the dosage of dimefluthrin, botanical substances can be added into mosquito repellent incense without reducing its effect. What is more, the resources of plants are huge in China, and plant substances can effectively inhibit or defer the formation of insecticidal resistance, so botanical substances are profound to be used in the field of mosquito control. Because octachlorodipropyl ether (S₂) is forbidden, and Piperonyl butoxide (S₂) is high cost, hence it is meaningful to explore novel botanical synergists in mosquito repellent incense to make up the vacancy of synergistic agents.This study systemically tested synergism of 269 sorts of plant extracts to dimefluthrin based on previous research at Research and Development Center of Biorational Pesticide. Research showed that:1. The preliminary screening of synergism of 269 sorts of plant extracts to dimefluthrin were tested by the bioassay method of sealed cylinder whith Culex pipiens pallensas, results showed that 9 plant acetone extracts out of 269 plants were tested to be synergistic to dimefluthrin. Synergistic ratios of Phytolacca acinosa,Linum usitatissimum, Scutellaria barbata, Rhizoma Dioscoreae and Smilax glabra. were bigger than 1.300, and synergistic ratios of typha angustifolia, Rubus idaeus, Tribulus cistoides and Sanguisorba officinalis were between 1.2500 and 1.3000. These 9 plant extracts whose synergistic ratio was bigger than 1.2500 would be tested with 5.8m³ square chest.2. Further screening of 3 plant extracts (root extracts of Phytolacca acinosa,seed extracts of Linum usitatissimum and inflorescence extracts of Typha angustifolia)synergistic to dimefluthrin were tested by the bioassay method of 5.8m³ cube chest whith Culex pipiens pallensas, exhibited higher synergism to dimefluthrin, of which extracts of Phytolacca acinosa exhibited best synergism to dimefluthrin, synergistic ratio of which was 1.2368 in sealed cylinder method. Synergistic ratio of root extracts of Phytolacca acinosa to dimefluthrin was 1.3622, synergistic ratios from both sealed cylinder and 5.8m³ square chest were higher than 1.2000. 3. Culex pipiens pallens as testing insect, sealed cylinder as bioassay method, insecticidal activity of three plant extracts, root extracts of Phytolacca acinosa, seed extracts of Linum usitatissimum and inflorescence extracts of Typha angustifolia were tested. Results showed that these extracts did not exhibited obvious insecticidal activity.4. Culex pipiens pallens as testing insect, sealed cylinder as bioassay method, formulas were tested by combining the most obviously synergistic root extracts of Phytolacca acinosa with seed extracts of Linum usitatissimum L. and inflorescence extracts of Typha angustifolia with different proportion, respectively. Results showed that the synergistic activity was highest when the propotion of root extracts of Phytolacca acinosa extracts and seed extracts of Linum usitatissimum was 1:1. Used 5.8m³ square chest method to test the activity of this mixture, results exhibited that the mixture of Phytolacca acinosa extracts and Linum usitatissimum L. seed extracts showed obviously synergistic activity to dimefluthrin.