Location: Sugarcane Research Unit
Title: SUPPLEMENTING NATIVE SUGARCANE BORER INFESTATIONS BY ARTIFICIAL INFESTATION Author
Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: May 3, 2007
Publication Date: June 13, 2007
Citation: White, W.H. 2007. Supplementing Native Sugarcane Borer Infestations by Artificial Infestation [abstract]. Journal of the American Society of Sugar Cane Technologists. 27:62. Technical Abstract: When conducting assessments of the response of sugarcane varieties to feeding by the sugarcane borer (Diatraea saccharalis), we routinely intercrop sugarcane (interspecific hybrids of Saccharum spp.) rows with a row of corn (Zea mays) and infest these corn plants with laboratory reared, first-instar sugarcane borer larvae. The raison d’être for this practice is the assumption that artificial infestation is required to obtain consistent and uniform insect pressure needed for varietal screening and yield-loss studies. On occasion, native infestations of the borer have been virtually non-existent or slow-developing and during those years it seems certain that infesting intercropped corn allowed evaluations to be conducted that would not have been possible with native infestation alone. We have not, however, previously attempted to quantify infestation intensities or determine the consistency of borer infestations resulting from the artificially infested intercropped corn. During the 2004, 2005, and 2006 growing seasons we collected infestation data from the corn intercropped among plots of sugarcane in our yield reduction studies with the objective of determining the uniformity and intensity of sugarcane borer infestations derived from artificially infested corn. Corn (Pioneer hybrid 3085) was intercropped with sugarcane in a 3:1 sugarcane to corn skip-row pattern on the following dates: 3 March 2004, 24 March 2005, and 27 March 2006. Planting in this manner resulted in each three rows of sugarcane being bordered by one row of corn. The corn averaged 5,300 plants per acre. We infested the corn using a hand-held inoculator the first week of May; a time corresponding to the first generation of sugarcane borer in Louisiana. We collected data on number of larvae per inoculation, percent of corn plants infested, number of adults emerging from each corn plant, percent of sugarcane stalks infested, and percent sugarcane internodes bored. Percent of plants infested (inoculated with 10 larvae per plant) averaged 65% producing an average of 145 adults per acre. By the third week in June, 30% of the sugarcane stalks in the yield reduction study were infested by sugarcane borer larvae. Year to year variability was high for infestation intensity, but bored internode counts revealed that, on average, the percent of the first five internodes bored was 20% (18% in 2006, 21% in 2005, and 22% in 2004). Our descriptive data indicate that we are being successful in initiating infestations of borer in our field evaluations and that these infestations occur early in the season, a time that the most economically important internodes are being formed. We will continue the practice of supplementing native infestations of sugarcane borer in our evaluation plots as the assurance of having a successful evaluation justifies the time and expense required to implement this practice.