Answer: Oleanders are susceptible to a bacterial gall or knot. Knots start out as small protuberances but grow into larger wart-like growths with rough surfaces. They can be about one-half to one inch in size. The bacteria enter through open wounds caused by pruning, frost damage or even natural openings in plant tissue. Splashing water or pruning tools can spread the disease from one plant to another. To treat, prune out all the infected parts and apply a solution of one part bleach to nine parts water to each cut. Wipe pruning tools with the bleach solution between cuts to help limit the spread. You can try trimming out the diseased portions, but new growth is often susceptible to re-infection. If large plants are severely infected, they may have to be completely removed. Note that all parts of oleander are poisonous. Wear protective clothing and do not burn the plant tissue as the poisonous fumes can be inhaled and respiratory difficulties created. Once established, oleanders can be hard to eradicate as they have tenacious root systems.
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