Black spots on fig tree leaves


#1

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.

We grow organic. Can anyone tell me what this is and how I can treat it organically? Pictures attached.Brown%20leaves%20on%20Smith%20IMG_2968%209-12-18|640x480 Brown%20leaves%20on%20Smith%20IMG_2969%209-12-18 Brown%20leaves%20on%20Smith%20IMG_2973%209-12-18


#2

I should add that the figs are also sharing space with 3 small apricots, 2 Chinese Honey Peaches, 2 Robadas and an Inca Plum.


#3

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.


#4

That was my initial thought, too. Although we have ventilation fans high up on both ends I felt that I also needed to get some floor fans to move air. Thank you for confirming my suspicions!


#5

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.

Infected fig

The fallen leaves infect whatever they touch.


More leaves

Mummified fruits

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.


#6

Thank you for weighing in on this. I am removing the dead & browned leaves as I go. What are the organic treatments for anthracnose?


#7

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?


#8

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.


#9

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.


#10

Brent: What about organic Neem Oil? I was researching the literature yesterday and it seemed to recommend Neem.


#11

I forgot to mention that I saw something that talked about Anthracnose in tomatoes. Do tomatoes carry this? If so I made a very grave tactical error in growing those in the same greenhouse.

We are going to find my old high school microscope - about 100 years old:-)) - and examine the leaves today.


#12

Had the same hot humid weather here in NY. Yes anthracnose has been a big problem for me this year on peaches and tomatoes.


#13

So I was correct that tomatoes may be affected or even spread it?


#14

Yes


#15

I think the neem would work well as a preventative, have had trouble with it burning leaves before though so have not really used any for a number of years.


#16

Thank you for that observation.