Be a Bonsai Sleuth: What is Needle Cast and What is Overwatering for Pines?
Many of the problems we see on our bonsai look very much the same. Needle Cast, a fungus, and overwatering, a care mistake, often look a lot alike.
Here are two photos that might help determine if you have one or the other of them in your yard:
This pine, a Ponderosa, has been overwatered. Notice the nearly equal lengths of browned tips. Whenever you see this, think, ‘This soil has stayed wet for too long.’ It may be because of water retentive soil, or perhaps it’s been watered too frequently. Adjusting the watering pattern for this tree, or changing its soil, should solve this problem in a year’s time.
This Ponderosa Pine has Needle Cast, a fungus. Notice the discoloration, the uneven browning of the needles, and the the green/yellow/red banding, especially in the green parts of the needle. The treatment for this tree is spraying with Daconil or a copper fungicide when the new needles are coming out. In most areas this means spraying in the springtime (though in some unusual areas such as the Pacific Northwest of the United States it can also be late summer and fall). It will usually take a year or two of careful management to get beyond this problem, so have patience.
Not that easy to tell apart, are they? And yet, identify which is which, apply the correction, and you’ll likely have success. Don’t identify it and you’ll likely have what history buffs know for certain…a repetition of the same thing over and over and over again. And again.
I’m glad that you brought up this topic because one of my larches has needle cast. I’m wondering, do I Daconil only the affected tree(s) or do I treat everybody? Is it species specific so I treat only the larches, or would I need to spray all conifers in the garden?
I am unfamiliar with the larch needle casts, so I’m sorry that I can’t comment on that-
If I were to make a guess though, many needle casts of multiple genera may be treated with Daconil—so that’s a possibility—but be sure it isn’t a tip blight which are often treated with other fungicides. Get a good identification of the fungus through a local Agriculture college, they often have labs to test them, or an independent tree service which also will have labs.
How do you tell the difference between these and the early stages of Diplodia tip blight, which has been showing up here in northern California?
Great post. Is there any value in removing the needles affected by the fungus?
Yes, if it is only a few needles. If there are more than that effected there is often more harm in taking them off than good, and spraying to prevent the new spores from starting new infections is the best route, and patience. Daconil prevents the spore from getting going.
Michael, Perfect post for me, as I am wrestling with this very issue now. The tree I have with brown tips is new to me, and I believe the soil is too water retentive, but I am not certain. It is hard to distinguish the difference between the two problems, as you note. Question: is there any harm in spraying a tree with Daconil as prevention? In other words, a person could monitor the moisture level carefully AND spray the tree, if unsure which problem the tree has. Also, if you have time (ha ha) it might be helpful to post a picture of several of the needles of the two trees laid out on a background that shows the difference. I think your most telling descriptor is the word “banding.” Luckily, I think I’m dealing with brown tips without the banding. Anyway, thank you for the excellent and very timely (for me) post.
Yes, prophylactic spraying is often done for pines in many areas because of the prevalence of pine needle casts. Be sure you’re spraying at the right time of year, be consistent, and you should have a turn around the next year.
Great article Michael, a friend of mine won a ponderosa pine in the auction at olympia. it barely has and new growth and has put on 7 giant cones, also has the fungus. i believe it’s in the throws of a decline and our weather here is wetter than your area. thoughts??d
Sounds like a good candidate for some spraying. I can’t say for sure of course without being there, but in the Northwest we have several needle casts and they can easily get the upper hand on bonsai which are already stressed simply by being in a pot. Ponderosas in our area also have trouble getting enough sun, so the tree will need to be in a very open area without big towering doug firs, etc— otherwise all the spraying may not do a lot.
I live in So. Texas and have several Japanese black pine. Predicated on the differing temperatures and seasonal differences would you know when would be a benefical time to spray?
The most important time to spray for most needle casts is when the needles are just beginning to grow. For a black pine that you’re decandling, that would be as the second flush is growing out.
Hi. Excellent article, I have some scots pine trees with fungus on the needles where I already applied fungicide but they have the white buttons (resin type) is normal ?!
Yes, the resin spots are common for needle cast damage areas. Keep up a spraying schedule as recommended on the bottle and expect to lose those needles in the next year, then hopefully the new needles will remain disease free.
Ohayo Gozaimasu, I own a Japanese BP and Ryukyu Matsu (Pine) with similiar needle damage, in my case I had camouflaged caterpillars feasting on the tips. I’ll keep a close eye on my trees for any further damage to verify if I’m over watering. Thank you for your post.
thank you Michael…..
On Mon, Jun 11, 2018 at 3:03 AM, Michael Hagedorn wrote:
> crataegus posted: “Many of the problems we see on our bonsai look very > much the same. Needle Cast, a fungus, and overwatering, a care mistake, > often look a lot alike. Here are two photos that might help determine if > you have one or the other of them in your yard: ” >
Michael – what about situations in extreme heat (100F or more) and in very low RH (today was 4% reported by my station) with regard to watering and watering a lot? I suspect the trees are fine and perhaps all the watering has been necessary but I am wondering if I run the risk of over watering even in these situations. I will say that while the top is bone dry, I have used the lift method to gauge just how dry my pines have been and the water goes quickly.
Great question— Certainly high heat and low humidity will make pots dry out faster. In most circumstances. But one does have to check, as you’ve been doing, that this is actually going on. The top will dry very quickly in such situations but the middle and bottom might not be. Trees can go into summer dormancy in summer and suddenly begin using much less water than they did the week before. Watering by rote is the thing to avoid—keep looking, keep asking if it’s really drying out or not.
Try a couple of the watering articles I’ve had on the blog here- just type ‘watering’ in the blog search field.
Hi Michael can needle cast kill your pine if not treated?
It can, it is one of the many diseases that isn’t a problem for a strong tree, even if it has a bit of it, but a weak tree can be taken down by it so that it loses so many needles that it can no longer support forward momentum.