Cindy asks: I have a Plumeria that keeps getting this orange colored fuzzy stuff on the underside of the leaves. And when you touch it, your fingers look like you’ve been eating Cheetos! (I call it the Cheeto disease.) What can I do to get rid of it?
The Scoop answers: The problem Cindy is having is a fungus called Plumeria rust that presents itself as tiny, raised, bright yellow or yellow-orange powdery pustules on the underside of the leaves. The spores are easily rubbed from the leaves, explaining why when Cindy touches them it looks as if she’s been eating Cheetos. On the upper leaf surface, yellow spots are visible. Plumeria rust can lead to premature defoliation of all of the plant’s leaves.
Why? Plumeria rust is carried by the wind from infected leaves and leaf debris, sticking to moist leaves of uninfected plants under wet or humid conditions. Heavy leaf canopy, reduced temperatures, and more moisture and humidity can all promote spread and growth of the disease.
Treat? Remove and throw away any infected leaves, whether they are still attached to the Plumeria or have fallen off, and do at first sign of disease. Then spray the remaining leaves with an approved fungicide to prevent additional rust development. Follow label instructions and rotate between fungicide products with different modes of action to inhibit the development of fungicide resistance in the fungus.
Prevent? To prevent the disease from forming new infections, plant your Plumerias in drier, less humid areas. While this can prove to be a difficult task in Central West Florida, we can reduce relative humidity and increase air flow in Plumeria canopy by preventing tall weeds from growing near Plumeria trees as well as not overcrowding Plumeria. Wider spacing will enhance aeration in the canopy and the drying of leaf surfaces after rainfall. Another way to prevent the fungus is to mix Plumerias with other plants that are not hosts of the rust disease. Space out Plumeria to increase air circulation and remove some of the leaves or branches late in the season to thin out the canopy.
Anything else? Plumeria rust is very difficult to get rid off and, with our climate, nearly unavoidable.
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