This morning my apple trees where just fine. At 6 PM I found that a lot of leaves turned yellow. Same happened last year: in two days half of the leaves dropped and the fruitlets followed in next few days. No single apple stayed. The weather pattern was similar - extremely hot for a few days and completely dry for 2 weeks. However, the mulched soil is pretty moist, so it shouldn’t be lack of water. The leaves look like diseased, but I can’t find any disease that goes that rapidly. Three trees on the front of the house is affected, the trees on the back is not. This is a city, nobody but me grow anything, so most likely not a herbicide damage. I am puzzled.
Leaf damage looks like scab. Have you sprayed for that?
No, I didn’t spray for scab. But should it be so rapid?
Couple of questions-
It appears only the small leaves (bract leaves) are effected. Are any of the large full sized turning yellow and dropping too?
Did you examine the dropped fruitlets and if so do they look normal?
What is your estimate of the % of fruitlets that dropped so far?
What are the cultivars of apple?
What roostocks are they on?
What type of soil- sandy, loam or clay?
Is there any differences between the front yard and back yard- soil differences, light levels, etc?
I’m not sure that I’ve seen it manifest as quickly as you described, but I do have a tree (a Crimson Gold) on which I’ve seen many leaves develop that appearance in less than a week. It’s never resulted in fruit drop, though.
See my responses below:
Contact your nearest agricultural university to see if you have a county extension agent nearby to send your pics to. Often these agents are up to speed on identifying your issue and telling you best practice to solve it.
For example here in western wa I go to these experts at WSU:
wsu extension office
Located in: Tacoma, WA
Closed ⋅ Opens 8AM Mon
Phone: (253) 798-7180
It could be scab. It also could be a different fungal infection. But the leaves that have yellowed are in a late state of infection and that makes it harder to tell. I would try looking for small bract leaves that haven’t yellowed yet and see what they look like.
Here are a couple of links that have pics of scab infections in the earlier stages to give you pictures you can compare to the small bract leaves that are still green.
Apple Scab: Improving Understanding for Better Management - Agriculture and Agri-Food Canada (AAFC)
I suspect what happened last year is the older small bract leaves were infected at earlier date sometime in the Spring and they harbored the infection. They then served as source of infection that later spread within the tree when conditions were favorable.
It also would explain why the disease spread was fast since the disease only needed to jump a short distance from leaf to leaf rather from the ground. The amount of spores would of been much higher too in this case. This link explains how the process works on cherries with cherry leaf spot.
Are these trees kept under netting? I see a netting cube in the background. That could raise the humidity levels around the tree and increase the likely hood of fungal infections.
While your checking the leaves you could consider doing a couple of things-
You could pick off the yellowed leaves. It looks like the tree is small enough to do that. This would help slow things down and give you more time to figure out what is going on.
I would consider spraying with sulfur if you’re an organic guy. If you’re okay with synthetic fungicides I would spray with Captan or Immunox or a mixture of both. That would put a protective coating on the larger still green leaves.
Is this the second year of the trees being planted? If so it is not that uncommon for some to take that long to settle down, specially if the weather stresses them, and you let them try to ripen fruit on year one.
My first five trees; one got knocked down before planting (wind, twice) and lost all the apples. I let the other four mature about five apples each. The next year the non apple bearing tree was trying to go gang busters, the other four were completely stunted; All four barely leafed out and had pretty much 0 growth for the entire season. The year after that (third then) they woke up in perfect health.
Ripening fruit is metabolically taxing to the point that even some established trees end up putting fruit every other year, needing a whole season to recover. Young trees should never be allowed to set fruit the first year and if you are eyeing maximum production not even the second year; this little sacrifice pays big time with larger crops from better established trees.
What varieties are they?
Thanks for detailed response. Under netting are sour cherry and plum, apples are not covered. I looked at the bract leaves more closely. I see some of them not yellow at all but with definite fungus spots on them. But I also see some yellow with green specks that has no obvious fungus spots. I will pick them up and spray Immunox this morning… However, I found that most affected tree should be scab resistant:
Ashmead’s Kernel has good disease resistance especially to scab and mildew, two of the most common apple tree problems.
They planted in 2017-2018, so they are not very young. The varieties are Ashmed Kernel on G41, Antonovka on B9 and and Yellow Transparent on G202
I saw scab on the leaves you showed. However, I think the problem is more than scab because your trees in the back do not suffer this issue.
I personally think the issue could be soil-related.
All of the trees that you listed ( Ashmead’s Kernel, Antonovka, Yellow Transparent) are moderately resistant to scab. I have a Ashmead’s Kernel and it gets scab but not as readily as my Roxbury Russet. Both of these still have quite a bit less resistance than my Enterprise tree which has the cleanest leaves in the orchard and is highly resistant to scab. It maybe the micro-climate in the front yard is different for some reason and it makes it easier for fungi to reproduce. Sometimes the micro-climate is different but we can’t see the difference.
I look at it this way. You can’t hurt the trees by spraying a fungicide. If the trees do have a fungal infection the fungicide will help them. Even if the infection turns out to be a leaf spot or a leaf botch the fungicide should help. It’s possible it is some kind of bacterial infection but I think that is very unlikely. If it’s a bacteria the fungicide would be ineffective. It’s also possible you’re seeing a combination of two things. A fungal infection with some heat stress from the recent weather which gives you a mix of yellowed bract leaves some with fungal spots and some without.
You might also take up DennisD’s suggestion and take a bunch of leaves in various stages of the disease to an extension office and see if they can help you get a diagnosis. Or post some pics of the green small bract leaves here and we can take a look at them.
If it were less sudden, I would think iron deficiency. Have you checked your soil ph?
You said the soil is moist. Sometimes the surface is moist but if you dig down a couple of inches it is dry. This happens sometimes when you just get light rains under dry conditions or you water with a sprinkler or hose. I would dig down a couple of inches in the soil and make sure it is moist below the surface. You might try this in a couple of locations around the tree.
If it has been hot and dry, and the tree that gets less direct sun is not having the problem, my guess would be heat stress and/or lack of water. Your soil may still feel moist a couple of inches below the surface, but if you have been having a hot spell, the moisture in the root zone has been depleted.
I propose to consider something like necrotic leaf spot. ?
While it is said to afflict Golden delicious And it’s sports…
I speculate similar things on other varietys.
Many different articles on line …
Some look , and fit with what you described.( Others not so much)
Sudden onset, corresponding with change to warm weather.
A physiological disorder ?
Your tree looks very healthy overall.
We had good snow cover and deep rains in April - beginning of May. Since then we had no rain at all and I didn’t water. I expect the top of the soil be dryer in this case than deeper. And yes, I dug down 2 inches when I checked the soil moister
How are your trees doing now? Are you losing more leaves or has the condition stabilized?