| Two-spotted spider mite Tetranychus urticae (Koch) is an important worldwide pest mites, has brought huge economic losses to agricultural production. Neoseiulus barkeri (Hughes) belongs to the euryphagous predator mites. Because of the short development period, low mortality, high spawning rate and the advantages of diffusivity, N. barkeri was considered to be one of the best biological control agents. This paper mainly discusses the toxicity and sublethal effects of bifenazate and etoxazole on T. urticae and N. barkeri, to provide certain theoretical basis for the protection of natural enemy, coordination of chemical control and biological control. The main research contents and results are as follows:1. Toxicity of bifenazate and etoxazole to T. urticae and N. barkeriThe results show that, the slide-dip method and leaf-residue method measured the LC50 of bifenazate on T. urticae female were 76.361 ug/mL and 26.537 ug/mL, respectively; Leaf-residue method measured the LC50 of bifenazate on T. urticae larvae and egg were 17.923 ug/mL and 19.298 ug/mL, respectively. The female of T. urticae were insensitivity to etoxazole, while the egg of T. urticae were extremely sensitivity to etoxazole, and the LC50 of etoxazole on T. urticae larvae was 2.363 ug/mL. Leaf-residue method measured the LC50 of bifenazate and etoxazole on N. barkeri female were 2.303 × 104 ug/mL and 1.938 × 103 ug/mL, but using secondary poisoning method won’t cause N. barkeri female death.2. Sublethal effects of bifenazate and etoxazole on T. urticae populationThe results show that Treated T. urticae female with sublethal concentration LCio and LC20 of bifenazate, oviposition period, reproductive and life span significantly reduced, were 4.25 d and 5.58 d,16.09 eggs/female and 5.58 eggs/female,5.00 d and 5.00 d, respectively. F1 generation juvenile period of females and males were significantly shortened, were 10.59 d, 10.19 d and 10.19 d,10.07 d, respectively. Oviposition period and life-span of female progeny extended, were 23.63 d,21.56 d and 27.00 d,23.95 d, respectively. The reproductive of female and male life-span were 167.98 eggs/female,167.98 eggs/female and 18.33 d,18.33 d, respectively, there is no significant difference with control.Population rm, λ, were 0.231 /d,0.233 /d and 1.261 /d,1.262 /d, respectively; Tc, Dt were 18.77 d,18.23 d and 2.99 d,2.98 d, respectively. When the eggs treated with bifenazate, the Ro, rm, and λ reduced with the increasing concentration,52.32 and 42.94,0.193/d and 0.177/d,0.177/d and 1.194/d, respectively. The Tc, Dt reduced with the increasing concentration, were 20.49 d and 21.17 d,3.60 d and 21.17 d. T. urticae larvae treated with subletal concentration of etoxazole, the survival rate decreased, although most of them successfully develop into adult stage, the female fecundity, life-span and male life-span were significantly reduced.3. The effects of treated prey with sublethal concentration of bifenazate and etoxazole on N. barkeri female and offspringThe results showed that, feeding prey that treated with sublethal concentration LC10 and LC20 of bifenazate, the preoviposition period of N. barkeri female extended, were 7.13 d and 6.38 d, respectively; the average female spawning was significantly reduced, were 36.41 eggs/ female and 36.41 eggs/female, respectively. The Ro, rm, and λ of F1 generation were significantly reduced, were 12.16 and 11.84,0.111/d and 0.111/d,0.111/d and 1.117/d, respectively; The Tc and Dt were significantly increased, were 22.53 d and 22.21 d,6.29 d and 22.21 d, respectively. Feeding prey that treated with sublethal concentration LC10 and LC20 of etoxazole, the preoviposition period of N. barkeri female significantly extended, were 7.43 d and 9.58 d, respectively. Oviposition period, fecundity declined significantly, were 31.78 d and 31.87 d, 31.54 eggs/female and 31.54 eggs/female, respectively. The Ro of F1 generation was significantly lower than the control, were 34.74 and 14.32, respectively. The rm, λ of Sublethal concentration treatment LC10 were lower than the control, were 0.128/d and 1.137/d; and the Tc, D, were significantly longer than the control, were 20.70 d and 5.43 d. But sublethal concentration treatment LC20 compared with control, except the Tc, while other parameters had no significant difference.4. The effects of feeding prey that treated with sublethal concentration drug on N. barkeri female functional responseThe results showed that T. urticae treated with sublethal concentration of bifenazate and etoxazole, can stimulated N. barkeri female feeding, searching effect also increased; at the same time the experimental results showed that feeding prey that treated with sublethal concentration drug, N. barkeri female functional response accord with Holling Ⅱ model, but the parameters changed. Feeding T. urticae female, the instantaneous attack rate a’increased with the increasing concentration, but feeding T. urticae larva, the a’decreased with the increasing concentration. Feeding T. urticae larva that treated with sublethal concentration of etoxazole, the a’and treatment time for prey Th of N. barkeri female decreased by the increasing concentration. |
PDF Full Text Request