What is the Potential of Sugarcane Borer in Reducing Sorghum Fitness and Grain Production?

Abstract

Pest attack is an important factor in the loss of sorghum productivity, and one of the main insect pests of grain sorghum is sugarcane borer (SCB) Diatraea saccharalis. Despite the importance of this insect species, little is known about the relationship between infestation and reduction in grain production as well as on economic thresholds for decision-making to control SCB populations. This study evaluated the influence of SCB infestation on plant fitness and grain production in three commercial grain sorghum hybrids. For this, the hybrids AG1090, BRS 373, and DKB 590 were planted in three crop seasons: March 2018 (2018/1) (crop season 1), September 2018 (2018/2) (crop season 2), and March 2019 (2019/1) (crop season 3). Six treatments were assessed in the experiments, consisting of the three grain sorghum hybrids with and without chemical treatment using the insecticide chlorantraniliprole (Altacor®) at 150 g ha-1 under SCB natural infestation. The parameters evaluated on sorghum plants were the length of galleries, plant height, length and weight of panicles, infestation intensity, and grain yield. The infestation intensities of SCB in the three crop seasons were higher when sorghum plants were not treated with insecticide, and consequently resulted in lower productivity. Regarding the difference between seasons, crop season 1 had lower infestation intensity. The hybrid DKB 590 had the lowest tolerance level, whereby insecticide treatment increased yield by 150% in crop season 1 (149.77 %). In crop season 2, hybrid BRS 373 exhibited the lowest increase in grain yield with insecticide control (29.79%), followed by AG1090 (33.13%), and DKB 590 (40.79%) with greater dependence on chemical control to increase yield. Crop season 3 obtained the lowest yield among the three crop seasons, and hybrid AG1090 responded better to chemical control, with yield increase of 105.90%, followed by DKB 590 with 54.26%, and BRS 373 with 38.19%. This is the first study that effectively shows how much grain production is lost by SCB attack in grain sorghum hybrids.

Keywords: Infestation intensity, Diatraea saccharalis, Yield, tolerance, IPM