First report of Diaporthe ambigua causing Phomopsis stem canker on sunflower in Argentina

Abstract

Phomopsis stem canker, a disease emerging on sunflower (Helianthus annuus) in response to environmental change, has already been described in Argentina with Diaporthe helianthi as the main aetiological agent (Ridao et al., 1994). During a survey (2020-2021) in the Argentinian sunflower-growing region of Pampeane, 208 sunflower plants with canker symptoms were collected from 75 cultivated fields (Fig. 1). Necrotic triangular dark leaf lesions invaded the stem, forming a conspicuous brown to black canker at the corresponding nodes.