Concern about additives to soil causing death of trees and shrubs - Ask Extension
We have a large wooded yard. In the past 2 years we have noted --in different areas of a nearly one-acre yard--groups of shrubs or trees that are comp...
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Concern about additives to soil causing death of trees and shrubs #889365
Asked November 05, 2024, 11:16 AM EST
We have a large wooded yard. In the past 2 years we have noted --in different areas of a nearly one-acre yard--groups of shrubs or trees that are completely dead after being vigorous for nearly 50 years. Even a large grove of bamboo has mysteriously died. We have never discouraged any bamboo disappearing, but it has been our experience that it is virtually indestructible. We have always maintained a completely organic approach to yard care and we have lived here for more than 35 years. We would like to have the soil tested in the various areas where the damage has occurred.
Please advise how we can proceed. Thank-you
Montgomery County Maryland
Expert Response
We can share information about basic soil testing (see linked page), but it only screens for nutrient content (not all nutrients, just most of the major elements), acidity level (pH), organic matter content, and when certain labs offer it, heavy metal levels. Unfortunately, while that information would still have value (especially if the pH were to be wildly out of the normal range), it probably won't help diagnose a problem affecting so many different species. A standard soil test can't screen for pathogens, pests, or herbicide residues. An environmental testing lab could test for chemical residues, but they would need to know exactly what compounds to look for, as they cannot test for the large number of chemicals and additives used in various pesticides (even organic pesticides). If there hasn't been a chemical spill, suspected misapplied pesticides (mainly herbicides, given the dieback issues), then a toxin is not likely the cause.
Did anything flood the property (or areas of dieback) prior to the plant losses? As resilient and invasive as running bamboo can be, for example, it still has its limits, and too little soil oxygen from oversaturated conditions may kill it, and can definitely kill other, more sensitive species. Was there any digging in the root zones prior to dieback, such as from construction, regrading, or utility work?
Trees die for a variety of reasons, including root loss, stress and secondary pest/disease issues, physical damage, girding roots, and so forth. It's not uncommon for decline and dieback to begin weeks, months, or even years before symptoms become prominent, making it hard to trace back the original cause. Even if different species die around the same time, they won't necessarily share a common cause.
A certified arborist or licensed tree expert can help evaluate struggling trees to narrow-down a diagnosis and look for sources of tree stress that might be able to be alleviated, either for that specimen or, if it's unsalvageable, for a replacement tree. If it's too late for the current trees (little can be determined if they are already fully dead or decline is advanced), you can try that approach if this keeps occurring in the future.
If you'd like us to make some educated guesses as to contributing factors, we would need to know what plants have been lost, what seasons they declined in (or at least when it was noticed as being prominent), and what symptoms manifested. For example, we've seen numerous examples lately of dead or dying 'Green Giant' arborvitae around central Maryland landscapes that succumbed to this year's prolonged drought. (Which in most of the state, has still not abated; see linked map.) The drought of this year, combined with last year's drought, and even the excessive rains of 2018 (and to a lesser extent, 2019) have all been stressing even mature, well-established plants.
Some species have a greater tolerance for wet soil (such as Pin Oak) while others have a greater tolerance for dry soil (such as Bur Oak), so each will be stressed or suffer root loss under different circumstances. Unfortunately, in recent years, we've experienced both extremes of precipitation at different times, and while winters have been mild overall, summer heat waves are also taxing some species. Those who lost lots of roots to soil saturation one year might be more easily damaged by drought a few years later, since the root system may not have recovered fully yet and can't keep up with the moisture demands of the canopy. Some pathogens, like Volutella Blight in boxwoods and Botryosphaeria and Hypoxylon cankers in many shrubs and trees, can become infectious and damaging when their host plants are under stress, when before they lived harmlessly alongside the same plant. Similarly, some wood-boring insects preferentially attack plants stressed by either too much or too little soil moisture.
We're happy to help puzzle-out what might be going on, but unless it's one event that impacted such a wide area, each plant might have to be assessed on a species-by-species basis, since their vulnerabilities to different environmental stress factors or pests/diseases won't always overlap. We can also provide feedback on the results of a soil test if you opt to do one.
Miri
Did anything flood the property (or areas of dieback) prior to the plant losses? As resilient and invasive as running bamboo can be, for example, it still has its limits, and too little soil oxygen from oversaturated conditions may kill it, and can definitely kill other, more sensitive species. Was there any digging in the root zones prior to dieback, such as from construction, regrading, or utility work?
Trees die for a variety of reasons, including root loss, stress and secondary pest/disease issues, physical damage, girding roots, and so forth. It's not uncommon for decline and dieback to begin weeks, months, or even years before symptoms become prominent, making it hard to trace back the original cause. Even if different species die around the same time, they won't necessarily share a common cause.
A certified arborist or licensed tree expert can help evaluate struggling trees to narrow-down a diagnosis and look for sources of tree stress that might be able to be alleviated, either for that specimen or, if it's unsalvageable, for a replacement tree. If it's too late for the current trees (little can be determined if they are already fully dead or decline is advanced), you can try that approach if this keeps occurring in the future.
If you'd like us to make some educated guesses as to contributing factors, we would need to know what plants have been lost, what seasons they declined in (or at least when it was noticed as being prominent), and what symptoms manifested. For example, we've seen numerous examples lately of dead or dying 'Green Giant' arborvitae around central Maryland landscapes that succumbed to this year's prolonged drought. (Which in most of the state, has still not abated; see linked map.) The drought of this year, combined with last year's drought, and even the excessive rains of 2018 (and to a lesser extent, 2019) have all been stressing even mature, well-established plants.
Some species have a greater tolerance for wet soil (such as Pin Oak) while others have a greater tolerance for dry soil (such as Bur Oak), so each will be stressed or suffer root loss under different circumstances. Unfortunately, in recent years, we've experienced both extremes of precipitation at different times, and while winters have been mild overall, summer heat waves are also taxing some species. Those who lost lots of roots to soil saturation one year might be more easily damaged by drought a few years later, since the root system may not have recovered fully yet and can't keep up with the moisture demands of the canopy. Some pathogens, like Volutella Blight in boxwoods and Botryosphaeria and Hypoxylon cankers in many shrubs and trees, can become infectious and damaging when their host plants are under stress, when before they lived harmlessly alongside the same plant. Similarly, some wood-boring insects preferentially attack plants stressed by either too much or too little soil moisture.
We're happy to help puzzle-out what might be going on, but unless it's one event that impacted such a wide area, each plant might have to be assessed on a species-by-species basis, since their vulnerabilities to different environmental stress factors or pests/diseases won't always overlap. We can also provide feedback on the results of a soil test if you opt to do one.
Miri
