Beet rust

Puccinia subnitens


In early spring, teliospores germinate from telial pustules after overwintering on inland saltgrass to produce basidiospores, which then are blown by wind where they can infect sugar beets or a number of other alternate hosts. The basidiospore infections give rise sequentially to the pycnial (also referred to as spermagonial) and aecial spore stages. Pycnial lesions are circular and light yellow, measuring 2 to 5 mm in diameter. Flask-shaped pycnia containing receptive hyphae and spermatia are found embedded within lesions and are located primarily on the upper leaf surface. Aecia, which develop directly from the pycnia after fertilization, are usually found on the lower leaf surface directly below the pycnia. The aecia consist of clusters of yellowish-orange, rounded structures that become cup-shaped after rupturing, releasing spores, and are often found aggregated in circular patterns. Newly formed aeciospores then re-infect the inland saltgrass, creating new uredia and telia, completing the life cycle.