Hi Folks We are growing figs in our 26’ X 48’ high tunnel for the first time this year. We planted tomatoes and peppers as the understory. We’ve had a blisteringly hot summer in Maine. The humidity in the high tunnel was high despite our opening the side walls for cross ventilation each day.
Our Smith fig developed what appears to be rust on the leave (rough and not glossy) and a few of these black dust areas. We planted too many tomatoes and they likely helped to hold in some of the humidity. Oddly only one of the smaller figs surrounded by tomatoes has this the others are not suffering from this. Just the Smith. The tree is fruiting, some leaves are curling up brown and falling.
I think the black stuff on the leaves is just a result of high humidity. I think it’s probably just on the surface, sort of like a mold. If your humidity is that high the fruit quality on figs probably won’t be that good. Other fruits may suffer also. Try to increase ventillation to lower the humidity.
It looks like the mildew caused when insects excrete sugary sap, check anything growing above those leaves for scale, mealybug, etc. The 2nd picture is a little more worrying, that might be the early stages of anthracnose, you should pick those off and dispose of them if the dead areas advance, here are some pictures.
Antracnose on leaves. Edit… These are all pictures of web blight, i believe.
The pale spots on your leaves could also be caused by fig bud mites, they are a microscopic species of eriophyid mite that spread fig mosaic virus and can also cause symptoms such as chlorotic blotching on leaves, dropping of new leaves (first picture shows that), browning on the interior of figs (yes, they spend time inside of figs), browning/russeting, and deformed leaves in the spring. They are hard to detect and also hard to eradicate, combined with an indifferent attitude towards FMV (which fig bud mite symptoms are often confused for) from sellers it has resulted in many new growers getting a rocky start. To confirm that is what caused the spots (other insects can cause similar spots as well) you need to look at the undersides of the newest leaves with a cheap handheld microscope (30-60x), they look more like tiny grubs than spiders or mites and move slowly, can be tough to see because new leaves are “hairy” with longer trichomes.
It seems to me like you are creating the perfect environment for pests to grow and survive, and giving them food. Also pests are more likely to attack trees if they are weak and stressed out, which I think is what is also going on, how hot and humid does it get in there?
Hi Alan: You are probably (unfortunately) correct. When it reaches 90 F the fans on either side of the top end walls go on. The humidity is high but I cannot tell you exactly what. I’m planning on correcting that. This has been very odd weather for Maine. Never seen such a hot, humid summer.
There are no fungicides approved for figs in the US, but Australia recommends copper. As long as you pick the leaf before it deteriorates to the point where the fungus has traveled down the petiole, or it drops onto another branch you should be fine.