Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: Atomic-S on 11/10/2014 03:44:17
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Being plagued by Bermuda grass under oleander bushes a number of years ago, I sprayed the grass with an herbicide (glycophosphate, I believe). It eliminated the grass. This actually took place on different occasions in different places over more than one year. Care was taken to avoid spraying the oleanders. In subsequent years but not shortly after the spraying, the oleanders sickened and mostly died out. At first I had thought that this was due to watering error, namely, too much water at one time and possibly too long intervals between waterings (this is southern Arizona where the summers can get very hot and the soil is alkaline and dense, although the oleanders grew well for many years prior to this). More recently, I have wondered if the herbicide could have had anything to do with it. Is it possible for this herbicide, used according to directions on low grasses under shrubs, to remain in the soil over a long period of time and migrate into the roots of the shrubs?
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Glyphosate degrades fairly quickly.
According to wiki it typically lasts 47 days (range 2 to 197) so anything happening in subsequent years isn't due to glyphosate.
It must be some other problem- a fungus or insect attack would be my guess.
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Glycophosphate is pretty much harmless to the soil, it works on the leaves and new shoots during the growing season.
As BC wrote, this is some other problem. In S. Arizona, I would suggest oleander leaf scorch could be the culprit. It is a bacterial disease, similar to that which causes grapevine & almond leaf scorch.