Impact Of Sublethal Doses Of Imidacloprid On Myzus Persicae, Tetranychus Cinnabarinus And Diaeretiella Rapae

The sublethal effects of imidacloprid on biological, ecological and biochemical characters of Myzus persicae (Sulzer), Tetranychus cinnabarinus (Boisduval) and Diaeretiella rapae M'intosh were investigated, respectively. The results will help to understand the sustainable influence of imidacloprid on target and nontarget pests. The main research results are summarized as follows:1 Influence of sublethal doses of imidacloprid on M. persicae1.1 Impact of sublethal doses of imidacloprid on experimental population of M. PersicaeThe impact of sublethal doses of imidacloprid on M. persicae was assessed by comparison of life table parameters, population trend index (I) and the interfering indexes of population control (IIPC) through the construction of the life table for the experimental population of F₁ generation. The results showed that longevity of F₀ generation was shortened and meanwhile there was a decreased fecundity; as for the population of F₁ generation, prolonged development duration and reduced r_m, R₀,λand I were observed. The values of IIPC were all less than 1. All these results suggested that there was a sustainable control effect of imidacloprid of sublethal doses on M. persicae.1.2 Time and dose effects of imidacloprid with sublethal concentrations on acetylcholinesterase of M. persicaeThe effects of sublethal doses of imidacloprid on acetylcholinesterase (AChE) of M. persicae were studied using microplate reader. The results showed that the specific activities of AChE in M. persicae reduced significantly after treated with different sublethal doses of imidacloprid; the K_m value of AChE decreased compared with that of the control while the V_max value of AChE increased. With change of time in LC₁₀, the specific activities of AChE changed and were restrained obviously; the K_m increased at the beginning and then decreased, and increased and then decreased, while the V_max increased constantly. Additionally, the results of the subcellular distribution of AChE in M. persicae with the treatment of the LC₁₀ sublethal doses of imidacloprid showed that the descending sequence of the activities of AChE was: microsome > cell nucleus and debris > mitochondrion > cytosol fraction; although the treatment of the sublethal doses of imidacloprid did not affect the subcellular distributions of AChE, the K_m and V_max changed significantly.1.3 Time and dose effects of imidacloprid with sublethal concentrations on carboxylesteras of M. persicaeThe results showed that the specific activities of CarE in M. persicae increased significantly after treated with LC₁₀ of imidacloprid while there was no significant difference of specific activities of CarE between LC₂₀ and LC₃₀ treatment; the K_m value of CarE decreased compared with that of the control while the V_max value of CarE increased at the beginning and then decreased. With change of time in LC₁₀, the specific activities of CarE changed; the K_m and V_max increased at the beginning and then decreased. Additionally, the results of the subcellular distribution of CarE in M. persicae with the treatment of the LC₁₀ sublethal doses of imidacloprid showed that the descending sequence of the activities of CarE in imidacloprid was: cytosol fraction > cell nucleus and debris > mitochondrion > microsome, while that of the control was: cytosol fraction > mitochondrion > microsome > cell nucleus and debris; although the treatment of the sublethal doses of imidacloprid did affect the subcellular distributions of CarE, the K_m and V_max, changed significantly.1.4 Time and dose effects of imidacloprid with sublethal concentrations on glutathione S-transferases of M. persicaeThe results showed that the specific activities of GSTs in M. persicae increased significantly after treated with different sublethal doses of imidacloprid while with higher doses of imidacloprid the specific activities of GSTs increased significantly; the K_m value of GSTs decreased compared with that of the control while the V_max value of GSTs increased at the beginning and then decreased. With change of time in LC₁₀, the specific activities of GSTs, the K_m and V_max changed and increased at the beginning and then decreased. Additionally, the results of subcellular distribution of GSTs in M. persicae with the treatment of the LC₁₀ sublethal doses of imidacloprid showed that the descending sequence of the activities of GSTs in imidacloprid was: cytosol fraction > microsome > mitochondrion > cell nucleus and debris, while that of the control was: cytosol fraction > mitochondrion > microsome > cell nucleus and debris; the treatments of the sublethal doses of imidacloprid did affect the subcellular distributions of GSTs but the values of K_m and V_max changed significantly.2 Influence of sublethal doses of imidacloprid on T. cinnabarinus2.1 Influence of exposure to imidacloprid on reproduction and vitellin of T. cinnabarinusThe results showed that there was no significant effect on both the hatching rate and larval survival rate when treated with LC₇₀ (23.4730 mg/L) dose of imidacloprid on the eggs, while sublethal doses of imidacloprid LC₁₀, LC₂₀ and LC₃₀ (0.5778, 1.4247, 2.7308 mg/L) led to significantly higher hatch rate and larval survival rate compared with the control; there was no significant change of adult longevity and fecundity of T. cinnabarinus with the treatment of imidacloprid and no change was observed in oviposition duration as well; vitellin did increase significantly between various of concentrations of imidacloprid and the water-treated control populations. After the exposure of adult mites to sublethal concentrations of imidacloprid, fecundity of T. cinnabarinus increased significantly, adult longevity also ascended significantly and hatching rate and larval survival rate increased significantly.2.2 Effects of imidacloprid with sublethal concentrations on three enzymes in T. cinnabarinusAfter the treatment of imidacloprid with sublethal concentrations, the specific activities of AChE, CarE and GSTs did not change significantly, that is to say, there was no time and dose effects of imidacloprid with sublethal concentrations on AChE, CarE and GSTs in Tetranychus cinnabarinus.3 Influence of sublethal doses of imidacloprid on D. rapae M'intoshThe results showed that safety coefficient of imidacloprid on D. rapae ranged from 5.5948 to 9.9080, and the toxicity ratio of benefit to harm amounted 24.7511, which revealed the safety of imidacloprid on D. rapae was relatively proper. However, there was some inhibitory effects of sublethal doses of imidacloprid on eclosion, adult survival and parasitism of D. rapae.In brief, there was some sustainable control effects of sublethal doses of imidacloprid on experimental population of M. persicae, time and dose effects on AChE, CarE and GSTs in M. persicae existed and the biochemical characters of subcellular distributions for AChE, CarE and GSTs were also influenced. Meanwhile, there was some inhibitory effects of sublethal doses of imidacloprid on eclosion, adult survival and parasitism on D. rapae. The study of sublethal doses suggested that the sublethal treatment might induce resurgence of T. cinnabarinus but there was no effect on the specific activities of AChE, CarE and GSTs in the species. The effect there was no effect on the specific activities of AChE, CarE and GSTs in the species. The effect of pesticide application on organisms is very complicated. It differ with the pest species, pest age and pest physiological conditions. However, It is very difficult to carry out the direct experiment to evaluate such influence. Nonetheless, the effects of insecticides on target pest, nontarget pest and natural enemy of target pest were systemically studied in the current paper and the results provides a new research avenue for the influence of insecticides of sublethal doses on pest insects.