ارزیابی خسارت کمی و کیفی ناشی از ساقه‌خواران (Lepidoptera: Noctuidae) Sesamia spp. در دو رقم تجاری نیشکر

Sugarcane is a strategically important industrial crop that has a prominent economic role in many countries around the world. The most important region for the production of sugarcane in Iran is the province of Khuzestan where it is cultivated on more than one hundred thousand hectares per annum, under the supervision of ten sugar agro-industries. As a mono-cultural system, sugarcane is sensitive to a wide range of biotic stresses including arthropod herbivores and pathogens. Moth stalk-borers are the most detrimental insect pests of sugarcane. Direct damage of stalk borers are caused by larval feeding at tillering stage, apical meristem is damaged and leaf changed to white color and caused dead-heart. During stem elongation, tunneling into stalks leads to reduced growth, weakening the stalks and resulting to stalk breakage. When severely damaged, stalks can rot; apical dominance can be lost resulting in the formation of side-shoots. The main indirect effect of stalk borers is reducing quality of sugar and purity. For investigation of stalk borers' effects on sugarcane quantity and quality, trial was carried out during 2014 harvesting season at Salman Farsi Agro-industry Ahwaz, Iran in a randomized block design with three replications. The commercial varieties under study were CP69-1062 and SP70-1143. In each variety, 400 whole stalks were sampled and they were put into five infestation level based on %internode bored 0%, 1-4%, 5-10%, 11-15% and >15%. At harvest season, quantity (height of plant, weight of one stalk and length of borer tunnels) and quality (%purity and brix) characteristics were evaluated. This assessment was conducted on three samples (replicates) of 10 whole stalks per variety grouped in five infestation levels. The results showed that height of plant, weight of one stalk, length of borer tunnels, %purity and brix were significantly affected by stalk borers. In CP69-1062, brix (20.7±0.18 and 17.9±0.1) %purity (90.3±0.13 and 87.3±0.12) length of borer tunnels (22.5±5.6 and 0±0.0 cm) weight of one stalk (890±7.6 and 825±2.9 g) and height (226.7±1.2 and 198.4±2.02 cm) were recorded for highest and lowest infestation level. In SP70-1143, brix (20.1±0.17 and 18.2±0.12) %purity (89.7±0.2 and 88.3±0.12) length of borer tunnels (18.6±3.9 and 0±0.0 cm) weight of one stalk (776.7±4.4 and 749±0.58 g) and height (211±1.53 and 194±0.58 cm) were recorded for highest and lowest infestation level. Our results indicate that stalk borers could significantly reduce the quality and quantity parameters of sugarcane and integrated pest management program should be applied to mitigate negative effects of stalk borers.