玉米螟不同虫态发生期、发生量对第1,2代玉米螟发生程度的影响

通过对第１，２代玉米螟各虫态发生期、发生量和为害率的连续调查结果分析表明：玉米螟各代的虫量基数只是影响当代发生程度的因素之一，并不能决定发生程度。玉米螟的发生程度与当代发生数量呈正相关，与田间落卵量关系更为密切，与发生时期关系不大。发生数理与发生历期呈正相关，第１，２代玉米螟的发生程度没有必然的联系，而表现为间断性和相对独立性。第２代玉米螟的田间产卵量是第１代玉米螟的３．７５～７．１倍，造成玉米被害率成倍增加。

Effects on Occurrence Extent of the First and the Second Generation of the Occurrence Time and Number of Different Stages of Maize Borer

Continuous sampling on occurrence time, number of population and rate of injury of different stage of 1st and 2nd maize borer have been carried out. Statistics results indicated as follows. The initial number of maize borer population was just one of the factors affecting on occurrence extent of the current generation, rather than a determinative factor. Occurrence extent of maize borer was positive correlated with number of the current generation, and had more relation with the number of eggs deposited in the field, little relation with occurrence time. Occurrence number was positive correlated with occurrence time scale. There was no necessary relationship between 1st and 2nd generations of maize borer on occurrence extent, Howere, it displaied discontinuity and relative independence. The number of eggs deposited in the field by 2nd generation was 3.75 to 7.1 times as which of 1st generation, therefore, the rate of injury increased by times.