3-Chlorophenoxypropionic Acid as a Plant Growth Regulator in Fruit Crops: A Critical Review of Crop-Specific Responses and Unresolved Mechanisms

This critical review examines 3-chlorophenoxypropionic acid (cloprop), its propionamide and Fruitone CPA formulations in peach/nectarine, pineapple, grape, and pecan. A structured literature update supplements known sources, distinguishing chemical identities and overlapping reports. Inspected direct reports span 1960–2026, driven by pineapple; grape and pecan evidence remains historical. Peach thinning responses vary with developmental stage, cultivar, and dose, while effects of tree physiological status remain hypotheses. Pineapple responses include delayed natural flowering, altered fruit maturation, and crown reduction, with protocol-specific efficacy and phytotoxicity. Hormonal measurements in treated peach and pineapple tissues do not establish a causal mechanism. The pineapple physiological experiment reported in a thesis and subsequent article combined delayed flowering with tissue injury and represents one experimental series. Grape evidence comprises one screening report; four historical pecan reports have important formulation, design, and harvest limitations. These crops delimit the review rather than encompass every investigated crop. Incomplete retrieval and citation tracing limit coverage. The synthesis supports chemically explicit, controlled research on unresolved responses and mechanisms. Historical findings do not establish contemporary efficacy, safety, or authorization. No application or dosing recommendations are provided; contemporary validation and jurisdiction-specific regulatory assessment would be required before practical use.