Submitted to: Inter-American Sugar Cane Seminars Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/6/1998
Publication Date: 9/6/2000
Citation: White, W.H., Legendre, B.L. Towards Cultivar Specific Economic Thresholds for Maximizing Profits and for Minimizing Field and Factory Losses to the Sugarcane Borer. Proceedings of the 1998 Inter-American Sugar Cane Seminars. 1:123-126. Interpretive Summary: Crop damage by insects is a major source to revenue loss by sugarcane farmers. Not only is there loss associated with crop damage, but there are also costs incurred with insecticide applications used to control damaging infestations. In Louisiana the insect most often causing economic losses is the sugarcane borer. Farmers in Louisiana must periodically apply insecticides to avoid excessive damage when larvae of this moth feed on their crop. Growers would benefit from knowing how each of the varieties that they grow respond to feeding by this insect. Our manuscript reports findings that characterize the damage associated with larval feeding on the major sugarcane varieties grown in Louisiana. Subject varieties were found to exhibit a wide range of responses to feeding by this insect. Some varieties were shown to exhibit remarkable resistance and therefore sustained little yield loss. Other varieties were remarkably intolerant to feeding and therefore suffered heavy losses. Provided with detailed information of this type allows growers to better manage each variety on their farm. For example, susceptible varieties should not be planted near waterways, schools, and housing areas. Resistant varieties would be better here. Also, resistant varieties may permit the grower to delay insecticide treatments long enough to allow other mortality factors such as ants and weather to reduce borer populations to below damaging levels. Less use of insecticides means greater profits for the grower and less damage to the environment.
Technical Abstract: The sugarcane borer is the major insect pest of sugarcane in Louisiana. Losses to this insect occur in the field and at the factory. Current economic thresholds in Louisiana recommend that sugarcane be treated with insecticides when 5% of the stalks sampled contain larvae behind the leaf sheath. This threshold was established over 30 years ago. Since then much has changed with respect to the cultivars grown, the methods of estimating quality of processed cane, cost associated with insecticide applications, and environmental and political consequences of making applications of insecticides. Experiments were conducted to establish cultivar specific economic thresholds for current commercial and candidate cultivars. Evaluations were conducted with half of the plots treated with insecticide and the other half not treated. Data analyzed as percent yield reduction were found to be highly variable with a significant cultivar within crop year interaction and a significant crop by cultivar within year interaction. Cluster analysis provided a useful procedure for summarizing data. A cluster group was found to contain cultivars resistant to the establishment of the borer and suffered little yield reduction. A separate cluster group contained susceptible cultivars that were heavily bored and suffered heavy yield losses. This study provides growers with detailed information on yield losses associated with borer damage and should help them effectively manage their cultivars by minimizing inputs as well as minimizing losses to borers.