Influence of Rice Leaf Morphology on the Folding Characteristics of Rice Leaf Folder, Cnaphalocrocis medinalis

The leaffolding characteristics of Cnaphalocrocis medinalis (Guenee.) (Lepidoptera: Pyralidae) larvae were studied on different categories of rice genotypes viz., resistant, moderately resistant, susceptible, hybrid, scented, popular and wild genotypes at AC & RI, Madurai, Tamil Nadu during 2005–2008. The larval starting point of leaf folds predominantly occurred in the distal midquarter and proximal midquarter of the leaf blades on the selected genotypes and least in distal and proximal quarter of leaf blades. The larvae performed more longitudinal folding than vertical folding, invariably on all the selected genotypes preferably on abaxial sides of the leaves than adaxial side. Only one leaf blade or blades of two leaves were involved in a fold, and folds with three and four leaves were rare. The presence of pupa within the leaf folds was significantly lower on resistant and wild genotypes. Results also revealed that the preference of leaf blades for feeding by larva was higher in the order of second from top > first from top > third from top > fourth from top and fifth from top in the entire selected rice genotypes. The correlation studies elucidated that the plant morphological characters viz., plant height and leaf blade length were negatively correlated to fold length and stitches per fold while, the leaf blade width was positively correlated.