Effects Of Insecticdes On Reproduction Of Brown Planthopper, And On Physiology And Biochemistry Of Rice Plant

Comparisons of stimulation effects of series of concentrations of four insecticides on the reproduction of Nilaparvata lugensNilaparvata lugens (Stal)(Hemiptera:Delphacidae) is a classical insect pest of resurgence occurrence which is induced by pesticides. Outbreaks of the pest frequently occur in Asia. The present study investigated effects of series of concentrations of four insecticides, imidacloprid, buprofezin, deltamethrin and triazophos, on preoviposition and oviposition durations (POD and OD), longevity of female (LOF), number of laid-eggs (NLE) and egg hatchability of N. lugens on two rice varieties, TN1and Xieyou963. The results showed that POD, OD, LOF, NLE and hatchability varied with insecticides, their concentrations, spray times and rice varieties. For imidacloprid and buprofezin, NLE and hatchability decreased, POD elongated, and OD and LOF shortened with increase of concentrations significantly. In contrast, for deltamethrin and triazophos, POD and OD shortened, LOF, NLE and hatchability increased with increase of concentrations significantly. Increase of spray times for the four insecticides amplified effects on these indices. For example, three sprays of deltamethrin significantly increased NLE and compared to single spray under the same concentrations and rice variety. In addition, rice variety also showed a significant influence on the indices. For example, NLE on TN1significantly increased compared to on Xieyou963under the same concentrations and spray times. Regression equations with significant correlation coefficients between each index and insecticide concentrations could be established for four insecticides on both rice varieties except for hatchability for single spray of buprofezin on TN1and for LOF for single of deltamethrin on TN1. The present findings have very important significance for the understanding of mechanisms of N. lugens resurgence and for management of the pest in commercial rice production.Imidacloprid-induced transference effect on some elements in rice plant and the brown planthopperThe widespread use of imidacloprid against insect pests has not only increased the rate of the development of target pest resistance but has also resulted in various negative effects on rice plants and Nilaparvata lugens resurgence. However, the effect of imidacloprid on elements in rice plants and the transference of these element changes between rice and N. lugens are currently understood. The present study investigated changes of Cu, Fe, Mn, Zn, Ca, K, Mg and Na contents in rice plants following imidacloprid foliar sprays and in the adult female of N. lugens that develops from nymphs that feed on treated plants and honeydew produced by females. The results indicated that imidacloprid foliar spray significantly increased Fe and K contents in leaf sheaths. Generally, Fe, Mn K and Na contents in leaf blades were noticeably decreased, but Ca contents in leaf blades for10and30mg/kg imidacloprid treatments were significantly increased. The contents of most elements except K and Mg in the adult females and honeydew were significantly elevated. Multivariate statistical analysis showed that Fe, Mn and Na in leaf blades and Fe and Mn in leaf sheaths could be proportionally transferred to N. lugens. The relationship between most elements in adult female bodies and in the honeydew showed a positive correlation coefficient. There were significant differences in the contents of some elements in rice plants and N. lugens from different regions. Effect of Ethiprole on reproduction of brown Planthopper and its effects on physiology and biochemistry of rice plantEthiprole (5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-(ethylsulfinyl)-1H-pyrazole-3-carbonitrile) is a phenylpyrazole insecticide, its compound acts on the y-aminobutyric acid-dependent neurotransmission system in insects. In the present study we investigated the effects of a series concentrations of ethiprole on the number of egg-laying (NEL) of Nilaparvata lugens (Stal)(Hemiptera:Delphacidae) and its effects on physiology and biochemistry of rice plants. The results showed that NEL decreased significantly with increase of ethiprole concentrations. The biochemical tests showed that the content of reducing sugar in rice plants varied with days after spray (DAS) and decreased significantly compared to control, also reducing sugar contents for all treatment decreased with increase of their concentrations but did not show significant differences between concentrations. In addition the contents of oxalic acid for all treatment decreased with increase of their concentrations but did not show significant differences between concentrations. We conclude that this finding have very important significance for the understanding of mechanisms of N. lugens resurgence and for management of the pest in commercial rice production.