Figs can drop leaves for several reasons, including drought, poor nutrition, and disease. The latter is what I will discuss today. The most prominent defoliating disease of figs in our region is fig rust. Unfortunately for those of us in Mississippi, I cannot find any labeled fungicides for control of fig rust. If you are in another state, check with you local county extension office for other options. Some publications recommend a “neutral (fixed) copper spray”, but I can’t find a product in the database that fits that description. The option is to make your own, called Bordeaux Mixture. These links will tell you how to make it:
Application should start just before budbreak in late winter. Application in hot temperatures (>80F) will likely cause damage to the plant. If rainfall and humidity is high then multiple application may be necessary about 1 week apart. Fixed copper fungicide sprays (e.g. tribasic copper sulfate, copper oxychloride sulfate, and cupric hydroxide) may also work for this and is somewhat less toxic to the plant once it starts to grow in the spring. This disease may be difficult to control fully in our environment when it is rainy and humid. The leaves will eventually fall off the tree and be replaced by new ones (see photo below). Sanitation (picked up and discarding infected leaves) is important for future control too.I suggest starting a spray regimen that continues through the spring. Since the fungus only infects leaves it is not a problem on fruit. However, lack of leaves can cause a reduction in following years fruit production and also a reduction in cold hardiness.Pruning trees to allow more sunlight penetration into the canopy and making sure the trees are spaced far enough apart may also help.