Valsa Canker of Apple in China: Can Host Nutrition Tame a Devastating Disease?

China is the world's top apple producer, with 44% of the world's apple-producing area in 2022. However, apple production in China suffers from a devastating fungal disease known as apple Valsa canker (AVC). AVC causes severe tree damage, and its control adds considerable labor and economic costs to growers. The traditional practice of surgically removing cankers does not prevent AVC recurrence. Eventually, AVC destroys tree vigor and leads to the abandonment of many orchards. Research on the etiology, pathogen infection biology, and plant-pathogen interaction mechanisms of AVC has accelerated during the past 2 decades. Studies at Northwest A&F University have shown that potassium nutrient status significantly impacts AVC resistance and can be exploited to manage AVC. In this review, we summarize research advances on AVC and emphasize that sustainable AVC management should focus on disease prevention through improvement of tree health via both belowground and aboveground measures. We discuss key factors related to tree health improvement and outline future basic and applied research needs relevant to sustainable AVC control.