川东地区玉米螟损失率测定与经济阈值

ECONOMIC THRESHOLD AND LOSS CAUSED BY ASIATIS CORN BORER IN EAST SICHUAN

玉米心叶末期,采用田间小区试验和被害单株减产测定,以研究玉米螟害对产量损失的影响。田间小区试验结果表明,花叶株率与玉米产量成极显著负相关,其回归方程y=23.88-0.1002x,即田间每增加1株花叶株平均减产50.1克;被害单株减产测定结果,平均花叶片数与单株平均减产数成极显著正相关,r=0.9104,回归方程y=8.3309+3.2177x,并由此计算得出,1株花叶株导致的田间产量损失:3.2177g/叶×5.6叶/株×2.67=49.83g/株,与小区试验结果基本一致。在公顷单产3750kg的玉米田,当每公顷用“广灭丹颗粒剂”15kg点心时,其经济阈值(ET)为花叶株率的4.1％。

Field plot and single plant tests were conducted at the late centtal-leaf stage to evaluate yield losses of maize induced by the Asiatic corn borer (Ostrinia funacalis) . Field plot test revealed a very close negative relationship between the percentage of 'mosaic' leaves (X) and maize yield(Y),the regression function being: y = 23.28-0.1002x,implying that increase of one 'mosaic' leaf would reduce 50.1g of grains on average. The result of the single plant test showed that the number of 'mosaic' leaves (X) was strongly possitively correlated with the mean yield incline (y) on single plants: y = 8.3309 + 3.2177x (r = 0.9l04 ..) from which calculation of yield loss per attacked plant could be performed as, 3.2177g/leaf x 5.6 leavs/plant x 2.67 = 49.83g/pl-ant, a result agreeing essentially with that of field plot experiment. If protection of a field crop with 3750kg/hm2 of yield is carried out with the method of dropping 'carbfuran' particles into the central-leaves, the economic threshold should be approximately 4.1% of 'mosaic' leaves.