Nitrogen fertilization enhances sugarcane borer (Lepidoptera: Crambidae) injury and survival in sugarcane

Nitrogen content of plant tissues is known to be a key factor influencing the development and reproduction of insect herbivores. Thus, nitrogen management often affects insect pests. The impact of nitrogen in sugarcane on the sugarcane borer (Diatraea saccharalis), has not previously been studied. Sugarcane borer infestations were compared among four rates of nitrogen fertilization (0, 50, 100, and 200 lbs/acre) in four field trials in 2017 and 2020. Trials in 2017 were conducted in HoCP 96-540 and HoCP 09-804 at the LSU AgCenter Sugar Research Station and the USDA Sugar Research Unit, respectively. Trials in 2020 were conducted at the same two locations using a split-plot design with cultivar (HoCP 96-540 or L 01-299) applied to the main plots and nitrogen treatments applied to sub-plots. In 2017, laboratory analysis revealed nitrogen content of leaf tissue was 1.5-fold greater in plots which received 200 lbs N relative to unfertilized plots. In all trials, the percentage of bored internodes and adult emergence increased with increasing levels of nitrogen . In 2020, injury was greater in HoCP 96-540 than in L 01-299. Relative survival was reduced in unfertilized plots relative to other treatments in 2017. In 2017, stalk weight increased with increasing N rates, but did not differ between 100 and 200 lbs. Similarly, in 2020, sugarcane tonnage and sugar/acre increased with increasing nitrogen, but did not differ between 100 and 200 lbs. Collectively, results demonstrate that nitrogen fertilization influences D. saccharalis infestations. Excessive fertilization can increase susceptibility to D. saccharalis.