Increasing nitrogen fertilizer rates lead to greater Diatraea saccharalis (Lepidoptera: Crambidae) injury in select Louisiana sugarcane cultivars

Authors: Penn, Hannah; WILSON, BLAKE - LSU Agcenter; VILLEGAS, JAMES - LSU Agcenter; Richard, Randy; Johnson, Richard

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2026
Publication Date: 2/26/2026
Citation: Penn, H., Wilson, B., Villegas, J.M., Richard, R.T., Johnson, R.M. 2026. Increasing nitrogen fertilizer rates lead to greater Diatraea saccharalis (Lepidoptera: Crambidae) injury in select Louisiana sugarcane cultivars. Journal of Economic Entomology. https://doi.org/10.1093/jee/toag030.
DOI: https://doi.org/10.1093/jee/toag030

Interpretive Summary: In crop systems like sugarcane, fertilizer is a vital part of production that is needed to boost yields. But pest insect damage may be higher on plants that have been given too much fertilizer like nitrogen (N), since this makes the plants better for the pests. But no study has looked at how applying different rates of N fertilizer impacts pest damage in Louisiana sugarcane where the main pest is the sugarcane borer or SCB. We used 3 field trials over 5 years to find if higher N rates increased SCB damage to plants and if this was the same across several commercial cultivars. We found that higher N rates had more pest damage but also greater yield. This happened in every cultivar we tested. We also found that applying higher N levels increased N and the amount of other nutrients like P, K, and Mg in the plant leaves, which might make the plant better for SCB caterpillars. To test if this was the case, we fed SCB diets made from plants grown at the different N rates tested in the field. We found that SCB gained more weight on diets with moderate levels of N compared to no N, showing that higher N makes the plants better for SCB. This study shows that while over-fertilizing sugarcane can increase yield, it may also increase pest injury and spraying costs.

Technical Abstract: Levels of plant nutrients, particularly nitrogen content, can drastically alter insect herbivory. In agricultural systems, nutrients, including nitrogen, are intentionally altered via fertilization to increase plant productivity. Prior studies found that greater nitrogen fertilizer rates can increase crop injury by Lepidopteran stem borers. However, little has been done to evaluate how nitrogen rates impact herbivory on local sugarcane cultivars by the primary insect pest in Louisiana, the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae). To assess this, D. saccharalis injury and yield metrics were evaluated in cultivars differing in D. saccharalis resistance with different nitrogen fertilization rates in five field trials conducted at three locations from 2017–2022. The influence of nitrogen rates on larval development was assessed in a laboratory assay. Higher nitrogen rates resulted in greater D. saccharalis injury and increased larval survival to adulthood but did not interact with cultivar. Greater nitrogen application corresponded with an increase in nitrogen, phosphorous, and potassium in leaves, potentially increasing the nutritional benefit to D. saccharalis. This was confirmed in the laboratory evaluation, where larval weights were greatest and development time shortest in moderate nitrogen-addition treatments. Despite the increased injury and developmental success with greater nitrogen, stalks weights and yield also increased, compensating for D. saccharalis-related losses. The present study aligns with findings in other sugarcane growing regions that nitrogen increases stem borer injury but not associated yield loss. Therefore, the adverse effects of D. saccharalis associated with higher nitrogen were minimal on the overall productivity of Louisiana sugarcane.