Changes in sugar cane quality and yield through damage by Sesamia grisescens.
Sesamia grisescens is a serious pest of sugarcane at Ramu sugar estate, Papua New Guinea. The larvae damage the apical meristem with consequent reduction in cane growth which is estimated to cause yield loss of 0.36 t cane/ha for each 1% of cane population with a dead top. The effect of top loss is amplified by invasion of the damaged stalk by Fusarium spp. The larvae also mine the expanded internodes of the cane stalk and cause a loss of 0.15% in pol (sucrose) for each 1% of internodes mined, with losses being relatively higher in the younger internodes at the top of the cane than in the lower, older internodes. Larval mining also results in increased fibre, glucose and fructose contents of the internodes and reduces the glucose:fructose ratio, indicating a preferential utilisation of glucose either by damaged tissues or by invasive microflora. Damaged internodes are characterized by an increase in raffinose content over the very low levels associated with undamaged cane.