RUSTS

• Pathogen:  Puccinia spp. Uromyces spp.
• Grasses Affected:  Annual bluegrass (Poa Annua), creeping bent grass (Agrostis palustris), tall fescue (Festuca arundinacea), bermuda grass (Cynodon dactylon) Kentucky bluegrass (Poa pratensis), red fescue (Festuca rubra), manilagrass (Zoysia matrella), tall fescue (Festuca arundinacea), zoysia grass (Zoysia japonica), emerald zoysia (Zoysia tenuifolia x Zoysia japonica).
• Season of Occurrence:  The primary time of the year when rust diseases are more severe are late summer and early fall.  However, they can also occur during spring, late fall and throughout the winter months if the air temperatures are moderate.
• Symptoms and Signs:  Early leaf lesion development is seen as light yellow flecks.  As these lesions enlarge, they may become somewhat elongate, and , in cases of high incidence, show definite orientation in rows parallel with the veins of the leaves.  Finally, with the rupture of the cuticle and epidermis, the lesions develop into reddish brown pustules.  As the pustules enlarge, the cuticle and epidermis that formerly covered each is pushed back to produce a characteristic collar effect, revealing yellow, red or brown spores.  In cases of high disease incidence, the leaves of the affected plants turn yellow, beginning at the tips and progressing toward the sheaths.  At this state of disease development, the entire stand of turf grass may appear yellow.
• Conditions Favoring Disease Development:  The development of rust is favored by a period of 2 to 3 days of (a) overcast or cloudy weather, (b) air temperatures in the low 70s, and (c) high humidity brought on by fog or frequent, light rain showers, followed by bright sunny weather with air temperatures in the 80s.  Rust is most severe on turf grasses under low nitrogen fertilization.