| Asian corn borer, which is the frequent corn pests in China, seriously affecting the yield and quality of corn, has been a problem urgent to solve. In recent years, with global warming, maize cultivars and cultivation model changing, the Asian corn borer occurrence regularity has changed, interval of the outbreak years continues to shorten (Lu Xin,2005; Zhou Shuxiang,2014). Under the new situation, the results of past studies can not accurately guide current prevention and control work to Asian corn borer. Revealling population dynamics of the Asian corn borer, borer resistance of different maize cultivars and yield loss damaged by Asian corn borer were critical for formulation and implementation of comprehensive management measures to Asian corn borer.This study cleared the population dynamics of Asian corn borer in the new situation through investigating the egg-laying of Asian corn borer and parasitic situation of it’s natural predator-tricho gramma; Furthermore, the borer resistance of common maize cultivars in Liaoning province were studied based on natural infestation; Maize conventional cultivar (LiaoDan565) and maize demonstrational cultivar (DiKa516) yield loss damaged by the second generation of Asian corn borer and it’s economic threshold were studied too, based on artificially infested field tests. The results are as follows:1. The survey of the egg-laying of Asian corn borer and parasitic situation of it’s natural predator-trichogramma had been carried out in Shenyang. The result showed that:the beginning date of egg-laying of first genegation were significant changed effected by early spring temperatures; the beginning date of egg-laying of second genegation were relatively fixed, which more concentrated in the July 24 to July 27; Intervals between two generations of egg laying shortened; The end date of egg-laying got later. Trichogramma parasitic was significant differences between generations. Egg parasitic rate of first generation was no higher 22.31%and the lowest rate being less than 2%; Egg parasitic rate of second generation was no lowest 48.78% and late up to more than 90%.2. Based on natural infestation, the borer resistance of 33 common maize cultivars in Liaoning Province were studied. The results showed that leaf feeding scales between different maize cultivars were significantly different (p＜0.01). XiWang3008, ShenHai49, LMin33, NinYu524, NongDa375, ZhengDan958, ZhongDan909, LiangYu99, JingDan28, XianYu023, PingAn194, TieYuan24, HuaNong887, XianYu 027, JingKe968, DanYu103 leaf feeding scale were less than 1, performed high resistance to the first generation borer; ShenYu21, NongDa108, TianNong9, GuanLi327, XianYu027, LiaoDan565, MC4592, HuaNong386, DongDan213, PingAn 169, DanYu405, PingAn186, PingAn166, DanYu405, XianYu335, FeiTian358 leaf feeding scale were between 1-3, performed resistance to the first generation borer; TianNong9 and JinQing202 leaf feeding scale were between 3-5, performed middle resistance to the first generation borer. All of 33 maize cultivars performed high stem resistance to the first generation borer, but ear damage rate were quite different between 33 maize cultivars.3. Field tests were conducted to infest the spring corn LD565 with a series of egg mass numbers (0,20,50,100 and 200 egg-masses per 100 plants). Results revealed that stalk holes per 100 plants and ear length per 100 plants were significantly different between different egg mass numbers (p＜0.01); Ear length, ear diameter, yield weight per plant and yield loss rate were all significantly different between stalk holes and ear length (p<0.01). Correlation analysis revealed that egg mass numbers per 100 plant and stalk holes numbers per 100 plant showed a significant positive correlation (r=0.982, p＜0.01); Stalk holes numbers per 100 plant and yield loss rate showed a significant negative correlation (r=-0.804, p＜0.01); Regression equations were y=3.1999x+24.8416 (R2=0.9525, P＜0.01) and y=0.0234.x-1.6167 (R2=0.9880, P＜0.01), respectively. Based on these two equations, the correlation between the number of egg-masses per 100 plant and corn yield loss rate conformed to the equation:z=0.0749x-1.0354. In conclusion, the economic threshold of using trichogramma form control Asian corn borer would be is 17.39 egg-masses per 100 plants in a field of 8411kg/hm2 per grain yield.4. Field tests were conducted to infest the spring corn DK516 with a series of egg mass numbers (0,20,50,100 and 200 egg-masses per 100 plants). Results revealed that stalk holes per 100 plants and ear length per 100 plants were significantly different between different egg mass numbers (p<0.01); Ear length, ear diameter, yield weight per plant and yield loss rate were all significantly different between stalk holes and ear length (p<0.01). Correlation analysis revealed that egg mass numbers per 100 plant and stalk holes numbers per 100 plant showed a significant positive correlation (r=0.9103, p<0.01); Stalk holes numbers per 100 plant and yield loss rate showed a significant negative correlation (r=-0.9797, p<0.01); Regression equations were y=81.65191nx-153.3374 (R2=0.9777, P＜0.01) and y=0.0244x-1.7078 (R2=0.9966, P<0.01), respectively. Based on these two equations, the correlation between the number of egg-masses per 100 plant and corn yield loss rate conformed to the equation:z=1.99231nx-5.4492 In conclusion, the economic threshold of using trichogramma form control Asian corn borer would be is 16.78 egg-masses per 100 plants in a field of 13104.9 kg/hm2 per grain yield. |
PDF Full Text Request