Impact of selected adjuvants combined with Vantacor against the sugarcane borer, 2023

The efficacy of 3 adjuvants combined with a standard rate of insecticide applied for sugarcane borer (SCB) control was compared with untreated controls in second ratoon sugarcane (HoCP 00-950) in 2023 at the USDA-ARS Sugarcane Research Unit Ardoyne Farm in Schriever, Louisiana. Plots consisted of 3, 60-ft rows, with 4 replications assigned using a RCBD. All insecticide applications used the insecticide Vantacor (FMC) at a rate of 1.2 fl oz/acre and were applied when the infestation reached the threshold level (3% of stalks with SCB larvae present in leaf sheaths) on 29 June 2023. Each insecticide treatment included 1 of 3 adjuvants: Destiny HC (Winfield at 1%v/v), InterLock (Winfield United at 4 fl oz/acre), or Latron AG-98 (Rohm and Haas at 4 fl oz/acre). One gallon of each combination was mixed in separate 2-gal tanks and applied with a DJI Agras T10 spray drone at 2 gal/acre. SCB injury was assessed prior to harvest (13 October 2023) by recording the total number of internodes, the total number of adult emergence holes, the internode location of each injury, and the number of bored internodes per stalk (12 stalks/plot). SCB injury per stalk was also split into thirds where the bottom third indicated early season damage, the middle third grand growth damage, and the top third damage nearer to harvest. Plots were harvested (18 October 2023) using a single-row billet chopper harvester and weighed using a weigh wagon with a billet sampler. Sucrose content was determined by analyzing a subsample of billets for percent fiber and theoretically recoverable sucrose (TRS) within 24 h. Plot weights were used to calculate cane yield (tons/acre) and then combined with TRS to estimate sugar yield (lb/acre). SCB injury, juice contents, and yield metrics were analyzed in R v.4.3.1 using generalized linear mixed models where block was specified as a random effect and using a normal distribution with means separated using Tukey’s honestly significant difference (HSD) (α = 0.05).

When the total percentage of bored internodes was evaluated, there were no differences among the treatments (Table 1). Similarly, there were no differences in the total percentage of emerged moths among treatments (P = 0.545, data not shown). However, when the stalk was split into thirds to evaluate the relative timing of damage, plots treated with the combination of InterLock and Vantacor had significantly less bored internodes in the bottom and middle thirds (Table 1). The top third of the stalks had very low levels of bored internodes, and no differences were observed among treatments (Table 1). The differences among treatments in bored internodes did not translate into any significant differences in fiber content, TRS, cane or sugar yield (Table 2).¹

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