Mildew Disease Decimates Impatiens Walleriana in Palm Beach

Impatiens walleriana, an evergreen perennial native to the tropical forests of East African, is the most popular plant for landscape beds in Florida and the nation. This year, beginning in January, downy mildew disease (Plasmopara obducens) began decimating walleriana plantings in Palm Beach, Fla.

The Palm Beach Post reports the annual planting of millions of colorful impatiens in Palm Beach County this year has resulted in countless numbers of the plants being pulled out because of downy mildew disease (Plasmopara obducens).

High daytime humidity and cool nights reportedly create the perfect conditions for the mildew disease. The disease is also affecting Europe and South Africa.

The Florida Department of Agriculture?EUR??,,????'???s Division of Plant Industry issued a pest alert on Feb. 9, 2012.

The disease, fortunately, only attacks the Impatiens walleriana variety, but unfortunately, that species is the most popular in Florida.

According to the University of Florida, impatiens are Florida's and the nation?EUR??,,????'???s most popular bedding plant.

When downy mildew disease attacks Impatiens walleriana, this is what?EUR??,,????'???s left. Two less common impatiens varieties, ?EUR??,,????'??SunPatiens?EUR??,,????'??? and ?EUR??,,????'??New Guinea?EUR??,,????'???, are not susceptible to the disease, but are more expensive and aren't available in as many colors.

Palm Beach County nurseries are disposing of large stocks of the plants, and won?EUR??,,????'???t be growing them next season. One local nursery normally sells some three million impatiens a year in 13 colors, but this year has thrown out about 150,000 impatiens.

The mildew disease is quite aggressive and the dieback happens fast. The first sign of the disease is white spores on the underside of leaves.

The failure rate of impatiens this year in Palm Beach County is estimated at 70 percent.