Pesticide-fertilizer synergistic alginate-based hydrogel for enhanced pesticide retention and nutrient optimization against apple Valsa canker

Abstract

The prevalence of apple Valsa canker (AVC) poses a significant threat to the vitality of apple trees, jeopardizing the progress of the apple industry. Current strategies have proven inadequate in managing the disease effectively due to challenges such as extended duration and frequent relapses, especially low-adhesion vertical target. Herein, we introduce a pesticide-fertilizer synergistic alginate-based hydrogel (P&F-Gel) to enhance long-term pesticide retention and offer nutrient supplementation without labor-intensive practices. By sequentially spraying a suspension concentrate with sodium alginate (SA) as thickening agent, followed by a cross-linked fertilizer (CCF) dominated by Ca²⁺ and other nutrient, rapid in-situ gelation is achieved on the low-adhesion vertical xylem surface. P&F-Gel demonstrates strong in-situ adhesion, long-term retention, and flush resistance, with temperature-triggered pesticide release making it suitable for field applications in humid and warm climates where AVC often breaks out. Additionally, P&F-Gel exhibits superior antifungal efficacy in vitro and in orchard, due to its capacity to isolate oxygen and inhibit fungal proliferation. Overall, our P&F-Gel represents the first use of a hydrogel strategy in trunk treatment, which provided a possibility to control AVC without intensive labor and protect apple trees from recurrence for over 6 months, paving the way for modern sustainable agriculture.