【摘要】 1983、1984两年在河南新乡七里营从不同虫量、不同世代、棉花不同肥力水平三个方面,采用同步人工模拟的方法研究了棉铃虫对棉花的危害,明确了下面几点:1.据田间定期调查统计,每头二代幼虫约危害10～13个蕾,0.5～0.6个顶尖,每头三代幼虫约危害8～9个蕾,0.3朵花,2.5～2.9个铃。被害蕾全部脱落,被害顶尖不能继续生长,被害部以下长出疯条,蕾铃数大减。部分被害铃霉烂甚至脱落,另一部分仅蛀食部位受损。2.二代棉铃虫危害期棉株受害后有足够的时间补足失去的棉蕾。在一定受害程度内不引起减产,轻度受害甚至增产。受害超过限度,因补偿棉蕾数不足,秋桃比例增加而减产。三代棉铃虫危害期棉株的补偿能力已大为下降,减产比二代棉铃虫引起的严重。3.二代棉铃虫为害期,不同肥力水平的棉花对幼虫危害的忍受力有显著差异。肥力水平高的补偿能力强,减产少或不减产。反之,肥力水平差的棉田受害后减产重。4.由虫量（自然对数）损失率回归线间的协方差分析表明:两年重复试验之间无显著差异;二代三个肥力水平之间 a 值差异显著、b 值差异不显著;二代低产及三代三个肥力水平之间无显著差异。得到下面三个回归方程:（?）=-14.59565+4.21216lnx±2.5（?）=-9.82564+4.21216lnx±2.5（?）=-13.56878+7.04571lnx±3.7y₁、y₂、y₃分别代表高产二代、中产二代、三代（包括低产二代）的损失率,x 为百株虫量。由此得出高产地二代防治指标是36头/百株;中产地二代防治指标是12头/百株;三代及低产二代下方治指标是8头/百株。更多还原

【Abstract】 In 1983 and 1984,simultaneous simulations of the feeling amounts of cotton bollworm,Heliothis armigera（Hbn.）were carried out in cotton fields of Qiliying,Xinxiang County,Henan Province,to determine its damage to cotton in three aspects:the larval densities,the generation of bollworm,and the fertility levels of cotton fields.The conclusions were as follows: 1,There were enough time for the cotton to compensate its loss of squares caused by the second generation infestations.When the damage was within a definite level,no yield loss would occur,and the yield might even increase if the damage was slight.However,the compensation ability of cotton decreased conspicously as the plants grew,and the squ- are loss became incurable in case a considerable damage of third genera- tion might take place and thus caused a more serious yield reduction than the second generation did. 2,During the second generation infestations,the tolerance of cott- on plants grown in fields of different fertility levels differed significan- tly.The yield loss in high fertility fields was small or none,as compared with a highest loss at the low fertility fields. 3,Covariance analyses of larval densities（natural logarithm）and percentage reduction in yield indicated that:the difference between years was negligible;the “a” values of regression equations of second genera- tion infestation at three different fertility levels differed significantly, While “b” values were not;no conspicuous differences among the regres- sion lines of the third generation infestation（including a slight second generation infestation）at different fertility levels were found. Based on the results mentioned above,the three regression equations obtained were as follows. y₁=-14.59565+4.21216lnx±2.5 y₂=-9.82564+4.21216lnx±2.5 y₃=-13.56878+7.04572lnx±3.7 where y₁,y₂,y₃ and x represented the percentage reduction in yield of second generation infestation at high fertility level,second generation infestation at medium fertility level,third generation infestation（inclu- ding a slight second generation infestation）,and larval densities per 100 plants,respectively;and the Economic Thresholds calculated from these equations were 36,12,and 8 larvae（prior to its fourth instar）per 100 plants,respectively.更多还原