Synergism Of Beta-cypermethrin Mixed With Three Adjuvants Against Three Insect Species

The co-toxicity of beta-cypermethrin mixed with azone, diesel fuel and JXL(a kind of trisiloxane surfactant) against 3 insects (Spodopteraexigua (Hübner), Helicoverpa armigera (Hübner) and Plutella xylostella (L.)) was investigated in this papper, also the penetrability and surface tension of these chemicals, epicuticle ultrastructure of Helicoverpa armigera treated with adjuvants was observed in lab, The main results were showed as follows.1. The synergistic interaction of azone, diesel fuel and JXL which mixed with beta-cypermethrin was assayed in Spodoptera exigua (Hübner), Helicoverpa armigera(Hübner) and Plutella xylostella (L.) by dip method in lab. The synergistic ratio is 1.55, 2.25 and 2.58, respectively, in Spodoptera exigua (Hübner) when beta-cypermethrin was added with azone at the ratios of 4:1, 2:1 and 1:2, which indicated that the synergism was enhanced with the azone content was increased. Samiliar results were assayed on beta-cypermethrin mixed with diesel fuel, and the maximum synergistic ratio was 3.61 in Spodoptera exigua(Hübner). The same synergism was also confirmed by beta-cypermethrin with JXL diluted 8000 and 16000 times in 3 insects. The synergism of beta-cypermethrin was further enhanced when the azone-JXL mixture or diesel fuel-JXL mixture was added.2. The penetrability experimental results indicated that the penetration time of beta-cypermethrin was 110s, and that of azone or diesel fuel was 62s or 78s, respectively. The penetrability of azone or diesel fuel was better than beta-cypermethrin. The cement layer was disappeared and the wax layer was partly destroyed in Helicoverpa armigera(Hübner) treated with azone(500mg/L) and diesel fuel(500mg/L) by scanning electron microscope(SEM) and transmission electron microscope(TEM), but there were no effects on arrangement of wax layer and cuticulin layer. There was positive correlation between penetrability of adjuvants and the destroy of insect epidermis.3. The surface tention of adjvants and beta-cypermethrin were determined, the results showed that critical micelle concentration (CMC) and the corresponding surface tension of the beta-cypermethrin were 125mg/L and 32.0 mN/m. The CMC of azone, dissel fuel and JXL was 500mg/L, 125mg/L, 125mg/L and their corresponding surface tension of 3 adjuvants was 29.5mN/m, 30.3mN/m and 19.0mN/m, respectively. The surface tension has remained at 19mN/m of beta-cypermethrin added with JXL diluted 8000 folds. The surface tension of JXL was the lowest among the tested chemicals.4. The penetration time of JXL was 39.90s, which was obviously less than beta-cypermethrin. The penentraion time was further shorten when beta-cypermethrin mixed with JXL. The epidermis could not wetted,in other words,formed liquid drop on cuticle of Spodoptera exigua(Hübner) and Helicoverpa armigera(Hübner) treated with beta-cypermethrin emulsifiable concentrate(EC) at 50mg/L and 125mg/L. Compared with beta-cypermethrin, JXL diluted 8000 folds wetted on epidermis in a split second, as well as beta-cypermethrin mixed with JXL diluted 8000 folds.