Submitted to: Sugar Bulletin
Publication Type: Trade journal
Publication Acceptance Date: 6/20/2000
Publication Date: 6/20/2000
Citation: White, W.H. 2000. Canes are not created equal or progress towards variety specific action thresholds. Sugar Bulletin. 78(10):27-29. Interpretive Summary: Louisiana sugarcane growers are continually seeing their profit margins diminish. A major expense is the cost of insecticide applications needed to control damaging infestations of the sugarcane borer. The current action threshold(the point where the grower must spray to avoid economic damage) of 5% of the stalks sampled containing larvae is based on the average response of varieties grown 30 years ago. The original pest management program considered all varieties as being equal in their reaction to the borer. As a result, resistant varieties often receive equal amounts of insecticides as susceptible ones. However, commercial varieties express a wide range in their response to feeding by the borer. We report research supported by Louisiana growers to establish variety specific thresholds for five of the most important varieties grown in this state. Although preliminary, it would appear that the published 5% infestation threshold for three of the major varieties is valid. The threshold could be increase for a fourth and should probably be lowered for a fifth. Thresholds that tell growers when they need to spray to avoid economic damage and set for individual varieties, would be a great benefit to growers. Such thresholds would help to maximize grower profits by avoiding unneeded applications and would minimize field and factory losses caused by poorly timed or unneeded insecticide applications. Fewer insecticide applications would also be important by reducing the risk of insecticide run-off into this sensitive agro-ecosystem.
Technical Abstract: For approximately 30 years, season-long control of damaging infestations of the sugarcane borer (SCB), Diatraea saccharalis, in Louisiana has been obtained by an IPM program. This multi-tactic program is composed of the following components: cultural practices , biological control agents, resistant varieties, and chemical controls. Insecticide applications are made only after weekly scouting of fields determines that infestation levels exceed 5% of stalks sampled with live SCB larvae in the leaf sheath. This threshold was established when the IPM program was first developed and was based on the average response of varieties being grown at that time. Present pest management practitioners have learned that varieties differ in their response to SCB feeding and have adopted the practice of adjusting thresholds upwards or downwards depending upon the variety. However, these decisions are based on intuitive judgements derived from trial and error and are not thresholds based on data derived from replicated field trials. This article, written for a trade journal, reports preliminary findings from research conducted to establish variety specific economic thresholds for the five major varieties currently being grown in Louisiana. The data from these experiments were obtained from replicated field trails with half the plots infested with borer and the other half kept borer free. Results suggests that the economic threshold will probably remain the same for three varieties; it may require increasing for a fourth variety; and decreasing for the fifth. If ultimately successful, variety specific thresholds will provide growers with information allowing them to be more efficient with their insecticide applications. Thus reducing the amount of chemicals going into the environment and increasing their profits.