Reed avocado, root rot and bacterial leaf spot
Question from Dave:
Here’s a photo of the Reed avocado. It was my strongest tree last summer. Full of dark green foliage. As the rains progressed through the winter it became progressively more yellow. The adjacent patio drains into its planter and then runs off to the driveway The feeding through the winter months was 2/3 cup per month of 6-4-6 commercial citrus avocado fertilizer. In March, I gave it 2 quarts of alfalfa and worm casting solids (left over from making alfalfa and worm casting tea for the roses) and also sprayed twice with ironite and gave it 1/4 cup blood meal and 1/4 cup bone meal The photo shows the yellowing leafs as well as new growth at the end of the branch. Because the leaf cover is declining, I’m white washing the exposed branches to protect them from direct sunlight. Thank you.
Answer from Pat:
Thank you for sending the photo of your Reed avocado. The leaves show the signs of salt damage, bacterial leaf spot and overwatering. The plant may also have stem rot. Salt damage can come from too much fertilizer building salts in the ground. Salt damage usually shows up in burned tips and burned (brown) leaf edges as are seen on some of the leaves in this photo. Over-fertilization can also lead to crinkled and burned (brown) leaves as shown on the lower left. Usually when a plant has been over-fertilized the leaves will become distorted and bent out of shape, sometimes in stunted form as can be seen with some of these leaves. But the main problem here comes from wet soil. Yellowing of leaves comes from over-watering (or too much rain) and from waterlogged soil. The brown blotches on the leaves come from bacterial leaf spot which results from overly moist conditions.
An old rule of thumb says “Do not feed a sick plant.” It sounds as if you might have been over-feeding this plant in winter when the soil was cold and the plant had already lost some roots due to root rot. When plants are growing in wet soils with poor drainage, fungi present in soil can rot roots. Feeding a plant just increases the problem. Weakened and rotting roots cannot take in sufficient nutrients for healthy growth. Hence leaves go yellow. In this case the brown may be caused by salts but also general necrosis from inability to take in nutrients. Bacterial leaf spot is also present from overly moist conditions. (The round lighter brown blotches are typical of bacterial leaf spot and may also appear sunken.)
In circumstances like that it is better to allow the plant to recover before feeding it. Soluble gypsum applied to the ground and watered in can improve drainage of clay soils and wash away salts. If I were you I would take off all yellow and brown leaves and any rotting, damaged or sunken twigs that might have stem rot, and hope for the best. You could try spraying the cuts with Serenade, but I doubt it will do any good. I also hope your avocado plant will recover but I am not sure it will do so because of the loss of so many roots and the difficulty of preventing the spread of the disease once it has invaded the plant tissues. If the plant doesn’t show signs of improvement in a month or two as the weather warms up, it’s best to yank it out, give it a decent burial and start over. If this happens, you can cheer yourself up with the thought that every horticulturist has had a few failures. A good idea would be to build a raised bed in that spot for any future planting. A raised bed does not need to be very high to correct drainage. It only needs to be 4 inches high to allow a new plant to avoid root rot. Fill the raised bed with top soil while creating a marriage of soils by mixing the lower with the upper soil and then dig straight through into the soil below to make the planting hole.
Thank you for the guidance. We cleaned out the diseased and dead leafs and twigs, applied Serenade and applied 2 lbs of gypsum. We can build a short wall around the planting area to keep the patio runoff out in the future.
Thanks for writing back. I always feel that when we take action and do what we can do that’s all that counts. I hope that your actions will show results, but in this case I’m not sure. At least you have done your best. Let us know in a few months how your avocado responds.
Greetings Pat!
I have a mini-orchard in my backyard consisting of ten different (mostly dwarf) fruit trees. All are thriving except my avocado. I have tried a Gwen, then a Reed in the same place (because there was no root rot) then a dwarf from Armstrong in a different location, and then another Reed in yet a third location (which is the best spot in my yard for sun). The trees have all had a 3 foot ring around them that I try to fill weekly with water during the hot months of summer. The tree was looking good until recently when the leaf tips have started dying and the edges have followed suit. The color is getting yellower in the surviving part of the leaves. My soil does have a good amount of adobe in it, so I try not to water too often. Lastly, the completely dead fringes of the leaves appear to have little holes in them that look like they might have been caused by insects…but I don’t know if they caused the damage or are just the work of an opportunistic insect that came along after the leaves’ immune system was compromised. Do you have any suggestions about what I can do? I really want to have a healthy avocado tree in my backyard that produces edible fruit! Thank very much for whatever you can do for me.
Gil
Sounds like poor drainage or alkalinity is harming root tips and this is leading to leaf burn, I see this problem on many home-grown avocado’s growing in a similar situation or in pots. I suggest apply gypsum. If this tree dies, test drainage before planting. (See page 68 of my organic book for how.) If drainage is insufficient, improve it: Build a large raised bed 4 inches high—that is sufficient!—, fill it with top soil but blend it with native soil instead of just dumping it on top so it does not form a horizon of soil there. Then dig right through it to plant your new tree. Dig 1/2 coffee can of gypsum into bottom of planting hole to increase drainage if problem is alkalinity of clay soil. Remember, also, that yellowing leaves might mean lack of nitrogen. I can’t tell you what the holes in leaves are but stressed plants often fall prey to pests.
Hi Pat,
I came upon this page when searching (fruitlessly – no pun intended lol) for questions about our avocado tree. Never had one before but moved into a new house that has a mature one that appears to be diseased (?). Not sure what care it had either.
At any rate, the leaves are yellowing (but not drooping) with some brown spotting that appears to be more on the top than the underside; some have small bunches of brown spots, others are more like big brown blotches. There are also some that look like the pic in this post (with the veins brown) but others have green veins and yellow leafy parts.
I checked for bugs but am not sure that I found anything… I have pics that I enlarged to see what look to be teensy (smaller than this: “.”) raised brown growths along some of the underside veins that had holes / entries (?) in them, as well as black specks that are even smaller (though, could that just be dirt?). I saw nothing that looked like a mite. A couple had spiders, and I saw a few bigger black ants (carpenter-looking).
Whatever’s going on, it’s affecting both new and old growth and there are many dead leaves scattered underneath.
I’d love to treat but am unsure where to start, especially having read your advice about not feeding a sick plant!
Any help you can provide would be greatly appreciated and I’d be happy to send pics should you need ’em.
Thank you so very much! 🙂
I suggest you fertilize and then mulch the tree over the fertilizer. Neglected trees are usually half-starved. Check that the tree is getting adequate moisture and not too much and does not have poor drainage. If soil is heavy clay, apply gypsum according to package directions just before a heavy rain and let the rain water it in. Do not try to cure the tree by spraying and do not rake up the leaves. If you can refer to a copy of my my month-by-month book, follow the directions for fertilizing avocado’s given in the February chapter or look in the February chapter of the Kindle edition of my organic book available from Amazon.com.