Bacterial wilt of annual bluegrass (Poa annua) caused by Xanthomonas translucens pv poae has become a serious problem of annual bluegrass in the Northeast. Annual bluegrass turf is predisposed to bacterial wilt by various stresses including intensive mowing and grooming, poor growing conditions, and ice formation during the winter. The increased incidence of the disease is most likely related to intensive management practices to increase green speed such as very low mowing heights, low nitrogen fertility, and aggressive grooming practices.
The disease tends to develop first in pocketed or shaded areas, high or low areas, periphery or clean-up areas, and wherever drainage is impeded. Symptoms first appear as small, yellow spots. Often etiolation (bleaching and elongation of foliage due to lack of photosynthesis) occurs, followed by wilt, collapse, and death of the plants. The putting surface may become speckled with numerous pits and in severe cases, spots will coalesce creating a general blight. The bacteria are spread by moving water and by mowers which create wounds and allow bacteria entry into the plants. Contaminated mowers can spread the disease to uninfected greens.
Correcting cultural practices that favor the disease can lessen bacterial wilt, but the bacteria are very difficult to eliminate.
- Mowing turf only when it is dry may slow the progression of the disease.
- Increase mowing height and reduce mowing frequency to every other day.
- Avoid mowing when greens are excessively wet and spongy.
- If possible, when the disease is limited to one or a few greens, a dedicated mower (preferably light-weight, walk behind mower with solid rollers) for these greens should be used to prevent disease spread.
- Grooming, aerification, and topdressing should be avoided when the disease is active.
Management with Bacteriacides
Chemical control options are virtually nonexistent. Antibiotics such as oxytetracycline may suppress bacterial wilt, but these products are phytotoxic, expensive, and not registered for use on turfgrass. General biocides such as copper (Kocide), JunctionTM (mancozeb), or ZeroTolTM (hydrogen peroxide) can reduce bacterial populations on leaf surfaces, but must be applied very frequently (after each mowing) which would result in severe phytotoxicity. The only truly effective management strategy is to eliminate annual bluegrass.
For a listing of fungicides currently labeled to manage this disease, refer to the Disease Management chapter of UMass Extension's Professional Guide for IPM in Turf for Massachusetts.
Written by: M. Bess Dicklow