Gardeners' thumbs will be turning a sickly shade of green this summer as the plant disease, Impatiens Downy Mildew, continues to rapidly infect America's flower beds.
According to a representative from the Master Gardener Program at Penn State Extension's Carbon county office, Impatiens Downy Mildew is a disease affecting standard bedding Impatiens as well as the double-flowered, miniature, fusion, and butterfly variations. New Guinea Impatiens are resistant to the disease.
Impatiens Downy Mildew is spread by spores that infect not only the flower, but the flower bed in which the plant grew. In the press release, "Guidelines for Growing," the Ball Horticulture Company said the disease has been recorded in the U.S. since 2004 but did not occur in regional outbreaks until the summer of 2011. By 2012, reports of Impatiens Downy Mildew were confirmed in 33 states.
The representative from the Master Gardener program said a flower that is infected with Impatiens Downy Mildew will first appear as if it is only in need of watering. Its leaves will begin to yellow before curling or flagging. The identifying symptom is a white coating of fungus on the undersides of the yellowed leaves. Eventually, an infected plant will drop leaves and flowers.
Once infected with Downy Mildew, the plant will not recover, and its stems will collapse in the final stages of the disease.
Impatiens Downy Mildew is a highly resistant disease with a lengthy infection period. Tom Ansilio, owner of the franchise company Flower Tent USA, said once the spores infect a flower bed, the bed will remain infected for the next three to four years. This fact was reiterated by the representative of the Master Gardener program who added that not even a series of harsh winters will kill the spores.
Workers at Flower Tent USA's Tamaqua site distributed an informational handout to customers that explained Impatiens Downy Mildew and provided gardeners with preventive measures. Gardeners are instructed to water their plants only in the morning, taking care to wet the soil and not the leaves.
At the end of the season, gardeners should remove plant debris from their beds. If the gardener notices an outbreak of the disease in their flower beds, they should remove all plants immediately to prevent the spreading of spores. Composting is unadvised, and infected plant beds should not be replanted for at least one full year.
Ansilio said standard Impatiens were the company's highest selling bedding flower but, because of the disease, Flower Tent USA will not be selling Impatiens in bedding trays for the next couple years. However, they will be selling some potted arrangements of the plant as potted Impatiens are not as susceptible. Despite losing their highest selling bedding flower, the business will not face significant losses as there are numerous alternatives such as Angelonia, Begonia, Coleus, Dragon Wing Begonia, New Guinea Impatiens, Sunpatiens, Torenia, and Vinca plants.