Chemical Control of ‘Prata Anã’ Banana Suckers by Pseudostem Application: Efficacy and Subsequent Soil Bioassay Responses

Effective banana sucker management is essential for plantation renewal because physical removal may allow regrowth from viable rhizome buds. This study compared localized pseudostem application of glyphosate (480 g a.e. L−1; 1.8 mL shoot−1), 2,4-D (720 g a.e. L−1; 1.5 mL shoot−1), and KH2PO4 + paclobutrazol (PBZ; 2.0 g + 1.0 g in 5 mL water shoot−1) with untreated, cutting, and mechanical controls in ‘Prata Anã’ banana. Phytotoxicity, chlorophyll indices, relative water content (RWC), mortality, regrowth, growth, and biomass were evaluated for up to 120 days after application (DAA). Soils collected six months after treatment application were subsequently evaluated using lettuce and tomato as bioindicator species, together with soil chemical characterization. Glyphosate and 2,4-D progressively impaired banana sucker physiology and growth. At 120 DAA, both treatments resulted in 100% sucker mortality, completely suppressed new sucker emergence, and reduced shoot fresh and dry biomass by 100% compared with the untreated control. The response to 2,4-D was faster, reaching 100% mortality as early as 28 DAA. In contrast, KH2PO4 + PBZ caused temporary physiological impairment, with RWC decreasing to 63.83% at 60 DAA and recovering to 85.56% at 120 DAA. Six months after field application, seedling emergence was unaffected by soil origin, ranging from 86.32 to 89.84% in lettuce and from 94.53 to 95.70% in tomato, and chlorophyll indices were also unaffected. However, species-specific differences occurred in growth, biomass, and Dickson quality index, while soil chemical properties differed among field treatments. Overall, localized pseudostem application of glyphosate and 2,4-D provided sustained suppression of banana sucker regrowth, whereas KH2PO4 + PBZ produced only temporary suppression. No consistent biologically detectable effects were observed across the bioindicator responses six months after field treatment application under the conditions of this bioassay. However, these responses cannot be attributed exclusively to chemical residues because the compounds and their metabolites were not directly quantified and soil chemical properties differed among treatments. From a practical standpoint, localized pseudostem application of glyphosate or 2,4-D can provide sustained sucker suppression, but the present bioassay does not establish a safe rotation or replanting interval, which would require direct residue quantification and evaluation at multiple post-application times.