Though it is more of an eyesore than a real life-and-death issue, there are times when fig rust, caused by Physopella fici, can be a very troublesome problem. Understanding its causes and the times of year it is likely to appear are keys to treating it. In most cases, the rust should not go untreated or could cause permanent damage. Not only will your trees begin to look unattractive, they may experience other problems, such as fruit loss.
The fig rust fungus is first noticed as smaller yellow-green spots on the leaves of the fig trees. These spots may enlarge over time and often will eventually take on a brown appearance as they spread. Eventually, the entire leaf will die and drop from the tree as the fungus continues its progression. It will also quickly spread to other leaves. The name "rust" is actually derived from the color many of these fungi produce on the leaves.
Rust can be particularly bad in some years and this is often dependent on the weather. All fungi tend to like wet and cool conditions and fig rust is no exception. The wetter the conditions, the more likely fig growers are to experience problems with the condition. Thus, you should always carefully inspect trees, especially when conditions are wetter than normal.
As fig tree rust continues to develop, the entire tree may eventually be affected. In fact, severe cases can actually produce a complete defoliation of the tree for the rest of the season. Fortunately, for those who like figs, this often happens after the tree has produced its crop of fruit for the year and been harvested. If you have a late-ripening species, then you may find that there are times when you will lose fruit as well.
Once you have determined that your tree may be at higher risk of attack because of the conditions or previous infections, then you should begin preventative measures. Before the first sign of rust the next season, spray the tree with an antifungal spray. May is often the best month to spray and more than one application may be needed, but this will likely be a matter of trial and error.
If you have trees that are possibly affected and have dropped their leaves, take the time to gather the leaves and dispose of them. These leaves can still harbor the fungus, even though they are off the tree. Therefore, new vegetation is still at risk of receiving spores from the dropped leaves.