Effect of leaf cutting at different growth stages on growth, yield and physiological traits of two rice cultivars

Leaf cutting tests simulating the damage caused by leaf folder,Cnaphalocrocis medinalis Guenee,were carried out to measure yield loss of rice at different growth stages( seedling stage,tillering stage and booting stage). Also, chlorophyll content and root system activity were measured after various extents of cutting( 10%,30%,50% and 70% in the seedling and tillering stage,10%,20%,30% and 50% in the booting sage) of the leaves of two rice varieties,super rice variety Yongyou 8 and japonica rice variety Ning 88. 10%- 70% cutting at the seedling stage and tillering stage did not affect rice yield and growth,and might actually increase rice yield. At the booting stage,yield was not affected when less than 10% of the leaf was cut; yield loss was less than 10% when 20% of the leaf was cut; and yield loss was 20%- 25% when 50% of the leaf was cut. Leaf cutting at the seedling and tillering stages caused little change in chlorophyll content,while root system activity was enhanced. This implies that rice has strong tolerance for leaf damage before the booting stage. We suggest that chemical control of the leaf folder can be reduced in the early growth period of rice.