Insect pest management approaches among currently recommended sugarcane varieties in Louisiana

The sugarcane borer, Diatraea saccharalis (F.), (Lepidoptera: Crambidae), is responsible for more than 90% of the total insect damage to sugarcane in Louisiana. The decision to apply insecticides is complex and influenced by numerous variables. Included among these variables are insect infestation levels, varieties, weather conditions, production input levels, and environmental concerns. Predicting damage that may result from infestations occurring at a particular time of the crop production season is also important. The objective of this research was to evaluate the impact of these variables on sugarcane borer populations and subsequent yield loss. Results from a two-year survey indicated a state average of 2% sugarcane borer damaged internodes in the 2000 growing season and revealed that most fields received only one application of insecticide. However, in Central Louisiana, where spring rainfall occurred, some fields required three insecticide applications for sugarcane borer control. In 2001, the survey showed a state average of 4% bored internodes, and most fields received less than one application of insecticide. In a two-year sugarcane borer management study conducted at the St. Gabriel Research Station, St. Gabriel, Louisiana, results from the plant cane crop (2001) and from the first ratoon crop (2002) showed some differences among the variety-management threshold regimes in percent bored internodes resulting from sugarcane borer larval feeding. For the resistant variety HoCP85-845, all thresholds for percent bored internodes were not significantly different from the untreated control, suggesting some flexibility in management when using the recommended 5% threshold level. In 2001for the highly susceptible variety HoCP91-555, the 10 percent threshold had significantly higher percent bored internodes than did the 5% and 5%/10% threshold treatments. HoCP91-555 also reached insecticide treatment levels before the other varieties. The selected threshold management regimes varied insecticide application timing and frequency to maintain sugarcane borer infestations below the designated thresholds. This study showed the importance of rainfall as a contributing factor for an increase in sugarcane borer levels and the role of resistant and highly susceptible varieties in a management strategy