Fig trees exhibiting rust spots on their leaves may have a fungal disease called fig rust. Fig rust defoliates an entire tree to defoliate in a year, according to Texas A&M University. Know the signs of fig rust in order to provide the best possible treatment.
Fig rust is caused by Physopella fici fungal spores. These fungal spores germinate and spread during the rainy season. Spores spread when the soil underneath the tree cools at night and a warm air current rises up the tree, carrying the spores to new leaves. Because the spores live underneath leaves, rain or washing the plant will not knock the spores off the fig tree.
The first notice signs are yellow to yellow-green spots on leaves. Eventually, these spots enlarge and turn brown. Leaves begin curling and fall off the fig tree. If the disease occurs early in the spring, the fig tree could defoliate and grow new foliage. The new foliage is susceptible to fig rust and cold injury.
Apply a neutral copper spray to your infected fig tree because it stops the fungal spores from spreading, according to Texas A&M University. Spray the tree with the fungicide once in May or June depending. Spray again three to four weeks later. Cover the fig tree with the fungicide spray. Direct the spray so that it coats both the top and the bottom of the leaves.
Mulch around your fig tree with an organic material, such as pine needles or compost. Spread a 3- to 4-inch layer of mulch 3 to 4 inches away from the tree's base of the tree. Do not let the mulch touch the base of the tree because fungal spores can live within the mulch. By allowing a free area around the base of the fig tree, fungal spores dry out from the sun. Applying fertiliser from March to September helps the tree fight the disease.