| The application of biochar to soils can improve soil quality and promote crop growth.In addition,biochar may contain population growth of herbivorous pests on rice.A growing attention has been attracted to the role of biochar in pest management program.There now lies a major challenge for the integrated pest management practitioners in how to coordinate agricultural practices and biological pest control techniques to achieve a sustainable management of agricultural pests.This thesis research examined effects of biochar amendments on developmental and reproductive performances of pesticide(buprofezin)resistant planthoppers of Nilaparvata lugens in laboratory experiments.In addition,a paddy field experiment was conducted to examine the effect on abundances of main pests and their natural enemies in paddy field of the eco-friendly techniques including biochar amendment to soils,Trichogramma parasitoid release,and field margin plantation.This research provides data for making ecofriendly pest management programs in paddy field.What follows is a summary of main results and conclusions from this research.1.Effects of biochar application on developmental and reproductive performances of buprofezin-resistant rice planthoppersThis laboratory experiment examined effects of biochar amendment to soils on life history traits of pesticide-resistant N.lugens.The experiment was designed by a factorial combination between two factors each with two levels: biochar amendment(yes and no)and buprofezin-resistance(high and low)of N.lugens.Groups of neonate nymphal planthoppers were followed on potted rice seedlings to assess their population growth potentials as measured by the Population Trend Index(PTI).The results showed that biochar and resistance interacted to affect population growth.Under the treatment of biochar application,the resistant planthopper had a marginally higher PTI(13.64)than the susceptible did(11.18);under the control the resistant planthopper had a nearly five times higher PTI(20.26)than the susceptible(4.84).The results suggest that biochar amendments to soils tend to decrease population growth of the buprofezin-resistant N.lugens compared to the susceptible strain.2.Effects of ecofriendly pest management on rice pests and their natural enemiesThree large plots in a paddy field were allocated respectively with three pest control practices:(1)ecofriendly pest management(EPM)including biochar amendment to soils,Trichogramma parasitoid release and field margin plantation of soybean,(2)pesticide application(PA),and(3)the control without any intervention to control pests.Sampling was made surveying the main pests C.medinalis and N.lugens and all relevant natural enemies across the season.Across the rice-growing season,density of the leaf-roller Cnaphalocrocis medinalis and N.lugens and leaf-rolling rate were lower in EPM plot than in the control during the early period while higher during the late period;Both pests and natural enemies were at lower levels in PA plot.Analyses of specific insect groups showed that average density across the season of C.medinalis and its rolled leaves,dragonflies,parasitoids,and spiders were similar in EPM and the control plot;the fly Sepedon violaceus and total natural enemies were higher in number in EPM plot than in the control;N.lugens was more abundant in EPM plot than in the control.The ratio between density of N.lugens and that of total natural enemies was 2.43 times higher in EPM plot(2.97)than in the control(1.22),suggesting the potential of biochar in suppressing the planthopper.The ratio between density of C.medinalis and that of total natural enemies was similar in EPM plot(3.16)than in the control(3.30),and the ratio between density of rolled leaves and that of total natural enemies was similar in EPM plot(0.35)than in the control(0.44).The results overall suggest that EPM plays somewhat a role in suppressing planthoppers,though has negligible effects on C.medinalis. |
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