Bacterial stalk rot is caused by the bacteria Erwinia carotovora subsp. carotovora and E. carotovora subsp. atroseptica. Bacterial stalk rot is primarily a disease of stressed or senescing plants, and infection generally occurs late in the season after extended wet periods. Infections occur in areas where water collects, such as leaf petiole axils, and is aided by wounds created by insect feeding (i.e., sunflower budworm), other pathogens such as Alternaria leaf spot, or mechanical injury. The bacterial stalk rot pathogens are readily disseminated in and among sunflower fields by splashing rain and irrigation water, as aerosols, and surface irrigation waters. The pathogens survive between sunflower crops in infected crop debris and as pathogens on many other plants, including potato, onion, and carrot.
Bacterial stalk rot symptoms first appear as a blackening of stems, often centered around a leaf petiole axil. The pith of infected stems is black and watery, and the rot eventually hollows stems. Plants often lodge as stems rot. Heads can be infected occasionally, causing a soft, watery rot that discolors seeds and flowers. The disease can reduce yield and seed quality, but is of little economic concern in the High Plains.
No biological control strategies have been developed for bacterial stalk rot.
Avoid rotations with susceptible crops such as potato and other vegetables. Do not reuse irrigation tail water from vegetable crops if sunflowers are irrigated. Practice strict sanitation of weeds, volunteer sunflower, and crop debris to reduce pathogen survival between sunflower crops.
No chemical controls are effective against bacterial stalk rot.
Categories: Sunflower, Disease, Bacterial Stalk Rot
Date: 3/10/2005