Two common ornamental plant diseases which occur during our
South Florida winter are guava rust (Puccinia psidii) and downy
mildew (Plasmopara viburni). We typically associate fungal
diseases with wet and warm conditions, but there are a few
pathogens which thrive in our “cooler” winter periods and do
fine with just a misting of water. Downy mildew attacks stressed
Awabuki (commonly referred to as mirror-leaf viburnum), a
variety of sweet viburnum (Viburnum odoratissimum). This species
can be recognized by the green-pepper fragrance when you crush
its leaves as well as the big dark green, shiny leaves. During
the winter, downy mildew will move in on weak plants and cause
spotting (light green to reddish-brown), yellowing and
defoliation. This is a minor disease usually, but it may cause
extensive defoliation. Once the hotter days of late spring
arrive, the disease tends to dissipate. A key point in control
is removal of fallen infected leaves. Get those out of your
landscape and do not mix them in with the co