Impact of insecticide, rate, and timing combinations against sugarcane borer, 2019–2020 Open Access

The impacts of treating sugarcane borer (SCB) infestations with standard rates applied at SCB threshold or higher rates earlier in the growing season (prior to SCB threshold) of 2 insecticides were compared to untreated checks in a sugarcane field of HoCP 09-804 in plant cane during 2019 and first ratoon during 2020 at the USDA-ARS Sugarcane Research Unit Ardoyne Farm in Schriever, LA. Plots consisted of three, 30-ft rows, spaced 6 feet apart, with 6 replications in an RCBD. Early, higher rate insecticide applications (Prevathon [chlorantraniliprole] 20 fl oz/acre or Confirm [tebufenozide] 8 fl oz/acre) were made on 5 June 2019 and 2 June 2020. Lower rate insecticide applications (Prevathon 14 fl oz/acre or Confirm 6 fl oz/acre) were applied at SCB threshold (5% of stalks with SCB larvae present in leaf sheaths) on 25 June 2019 and 29 June 2020. All insecticide treatments were mixed with a surfactant (Interlock Winfield United at 4 fl oz/acre) in a 5-gal container of water and applied with a Lee Agra Highboy Sprayer at a 40 psi and 10 gpa. SCB injury to sugarcane was assessed immediately prior to harvest (13 November 2019 and 5 November 2020) by counting the total number of internodes and the number of bored internodes and SCB adult emergence holes per stalk (12 stalks/plot). Plots were harvested using a single-row billet chopper harvester and weighed using a weigh wagon with sucrose content determined by analyzing a subsample of billets for percent fiber and theoretically recoverable sugar (TRS) within 24 h. Plot weights were used to calculate cane tonnage (tons/acre) and then combined with TRS to estimate sugar yield (lb/acre). Bored internodes, juice contents, and yield metrics were analyzed in JMP v14 (SAS Institute) using generalized linear mixed models with a normal distribution and means separated using Tukey’s HSD (α = 0.05).

There were significantly fewer bored internodes in plots treated with Prevathon relative to untreated check plots in 2019 plant cane (Table 1). Plots treated with Confirm had lower levels of bored internodes than the untreated check plots, but were not significantly different (Table 1). Additionally, there were no differences in bored internodes between the early-applied higher rates and the lower rates applied at SCB threshold for either Confirm or Prevathon (Table 1). Though not significant, Confirm-treated plots tended to have more bored internodes later in the season/higher on the stalk with early applications. There were no significant differences in bored internodes among treatments in 2020 (Table 2) as SCB damage was low. Only 2 adult moth emergence holes were documented in 2019 and 1 in 2020, so these data were not analyzed. There were no differences among treatments in fiber (which was generally high for this variety) or TRS in either 2019 (Table 1) or 2020 (Table 2). Similarly, there were no significant differences in cane tonnage or sugar yield among treatments in either 2019 (Table 1) or 2020 (Table 2).¹

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