关键词: 白背飞虱, 稻纵卷叶螟, 褐飞虱, 组合侵害, 籽粒生长

Abstract: According to the characteristics of occurrences of the three insect pests Sogatella furcifera, Cnaphalocrocis rnedinalis, Nilaparvata lugens in Jianghua rice district, their combined infestations and effects on grain growth of rice werestudied in paddy field and cement pool with cage by random plot design of complete combination in 1991-1992. Weights of the strong grain and the weak grain were determined once every four days from heading to harvesting. The growth equation, W=K was used to describe the grain growth process of each treatment.From first, second and third order derivatives of the equation, some parameters were derived as follows: a Bk Kbe' * ~-~,Vm,x~ '4- 'dr =tz-tl,CT-Vm~,. ('2-*l),R0'== (1 -t- e~)2where t=turning point of growth curve, V_max=maximum growth rate, △_t=activegrowth stage, (grain growth becomes slow before t₁ and after t₂), GT= cumulative weight of dried content in active growth stage, and R₀=initial growth power. Effects of combined infestation of the pests on the strong and the weak grain growth were analysed by these parameters. The results of analysis of variance showed that interaction effects were also significant in addition to the main effects of the combined infestations on yield which were significant. This indicated that the combined infestations of the pests caused economic damage even though density of each species was below economic threshold. Values of V_max GT t and K decreased as the infestattlons aggravated. Moreover, the result of analysis also showed the effect of the infestation on the weak grain being greater than that on the strong grain.

Key words: Sogatella furcifera, Cnaphalocrocis medinalis, Nilaparvata lugens, com- bined infestation, grain growth