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black twig borers, Xylosandrus compactus

Q: My neighbor’s oak died suddenly. What could have caused it?

Q:  My neighbor’s oak died suddenly. Now mine is doing poorly and I wanted to be sure it wasn’t a disease that might spread to mine.  What could have caused it?

A:  Thanks for bringing me cuttings of your oaks; one was a Laurel Oak and the other a Sand Live Oak.  It was important to us to be able to identify your oaks then determine what might be causing their decline. We were able to eliminate construction damage and poor pruning on your trees although that may have been what started the decline on your neighbor’s trees.  Compacted soil around the roots is another stress factor for trees so we discussed adding pine straw under the tree canopy and adding water to be sure the roots are hydrated.

After examining the twigs we discovered black twig borers, Xylosandrus compactus.  This is one of the few ambrosia beetles that will infest healthy trees, in fact, 224 species of trees are susceptible to infestation.  Most ornamental shrubs and trees do not die from the infestations but the twig borers can cause stem dieback which can be unsightly.  With additional environmental stress such as drought, construction or compacted soil around the root area; the tree may eventually die. In north Florida, adults spend the winter in damaged twigs of host trees and emerge during late February.  The females attack new twigs in March and brood production begins in April. Highest population levels occur from June to September.  Best management practice is to remove any fallen twigs and/or prune damaged twigs to control this beetle.  Regarding your trees, it was evident the Laurel Oak showed greater depth of decay from the beetle than the Sand Live Oak.  I suspect you may see the decline of the Laurel Oak before the Live Oak as the Laurel is less able to compartmentalize the decay.  Consider hiring certified arborist to come and do some corrective pruning if necessary.  You can locate a list of certified arborist in this area by going to the Florida Chapter of the International Society of Arboriculture: