Ornamental fruit trees dropping brown leaves - Ask Extension
Our ornamental crabapple has been turning orange and dropping its leaves for the last 3 years. Local extension agent thought it was a fungal problem....
Knowledgebase
Ornamental fruit trees dropping brown leaves #869202
Asked May 20, 2024, 9:59 AM EDT
Our ornamental crabapple has been turning orange and dropping its leaves for the last 3 years. Local extension agent thought it was a fungal problem. Have been spraying w/Immunox regularly to no avail. The ;eaves in background of closeup are 1 week's accumulation after last mowing.
This year a neighbor's ornamental (not crabapple) seems to be having a very similar problem. Progression of discoloration is different but same results.
Is this fungal or something else? What is the proper course of action? What is the life expectancy of the tree?
Charles County Maryland
Expert Response
The symptoms pictured don't imply a fungal infection to us, though to be fair, crabapples as a group are vulnerable to several diseases. The image titled "Ray's tree"...is that the same tree or the neighbor's tree that you mentioned? It does look like a crabapple also (there are hundreds of varieties, most ornamental, but some edible), and its damage looks like phytotoxicity. (That is plant tissue damage from chemical exposure.) Do you know if anyone applied any type of pesticide on or near either tree prior to each year's expression of symptoms? There are conditions in which any chemical intended for use on plants can still cause damage if applied in just the right conditions (such as when it's too warm) or if it's accidentally overdosed. Was any weed killer used in the lawn that surrounds the crabapple?
The crabapple's symptoms suggest environmental stress, which could involve several factors like soil moisture level (too wet? too dry?), drainage (does anything add water to the area, like a nearby roof downspout?), or possibly injury to the trunk. We notice that lawn looks like it's growing right up to the trunk, with no mulch circle, which can risk injury to the bark from mowers or weed-whackers. If that happens, there is no treatment for such a wound, and opportunistic wood-boring insects or wood-decay fungi can enter the trunk and cause damage. A compromised root system (was any digging done in that area in the past few years?) can also result in premature leaf shed, which is what appears to be happening here.
Crabapples are somewhat short-lived trees (perhaps 20-30 years) given the range of ailments they can contract, but this can also depend greatly on how stressed (or not) a tree is over the course of its life, and whether an injury or other event allows for a pathogen or pest to gain a foothold that happens to cause serious damage to the live wood under the bark.
There is no cure for wood decay, no treatment for borers already in wood, and no other actions we'd recommend at this stage with regards to chemical intervention. If herbicide sensitivity/exposure did occur, the tree will have to outgrow the damage as best as it is able, and ideally in that situation the exposure is not repeated in a future year. Fertilizer should not be needed, but if you suspect a soil nutrient deficiency or out-of-range acidity level (pH), you could have a laboratory soil test performed to see if anything is amiss. (We can help to interpret the results if desired.) This doesn't look like a situation where soil testing will provide much information, but it's hard to say with certainty, and aside from the minor testing fee, it wouldn't hurt to try.
This is a less-likely cause, but...is there a buried gas line that might be leaking? A source of ethylene gas can cause premature leaf drop in plants, and some plant species can be more sensitive to ethylene than others. Is the tree growing near a driveway or road where a vehicle is regularly idled, where exhaust would be drifting into its canopy?
Miri
The crabapple's symptoms suggest environmental stress, which could involve several factors like soil moisture level (too wet? too dry?), drainage (does anything add water to the area, like a nearby roof downspout?), or possibly injury to the trunk. We notice that lawn looks like it's growing right up to the trunk, with no mulch circle, which can risk injury to the bark from mowers or weed-whackers. If that happens, there is no treatment for such a wound, and opportunistic wood-boring insects or wood-decay fungi can enter the trunk and cause damage. A compromised root system (was any digging done in that area in the past few years?) can also result in premature leaf shed, which is what appears to be happening here.
Crabapples are somewhat short-lived trees (perhaps 20-30 years) given the range of ailments they can contract, but this can also depend greatly on how stressed (or not) a tree is over the course of its life, and whether an injury or other event allows for a pathogen or pest to gain a foothold that happens to cause serious damage to the live wood under the bark.
There is no cure for wood decay, no treatment for borers already in wood, and no other actions we'd recommend at this stage with regards to chemical intervention. If herbicide sensitivity/exposure did occur, the tree will have to outgrow the damage as best as it is able, and ideally in that situation the exposure is not repeated in a future year. Fertilizer should not be needed, but if you suspect a soil nutrient deficiency or out-of-range acidity level (pH), you could have a laboratory soil test performed to see if anything is amiss. (We can help to interpret the results if desired.) This doesn't look like a situation where soil testing will provide much information, but it's hard to say with certainty, and aside from the minor testing fee, it wouldn't hurt to try.
This is a less-likely cause, but...is there a buried gas line that might be leaking? A source of ethylene gas can cause premature leaf drop in plants, and some plant species can be more sensitive to ethylene than others. Is the tree growing near a driveway or road where a vehicle is regularly idled, where exhaust would be drifting into its canopy?
Miri
