Question

holes on eucalyptus li   QUESTION: I just like to ask whether the attached eucalyptus tree pic is infested by borer insects. I have read so much of this pest but I'm not sure if the holes on the limbs are caused by borer insects particularly the longhorned beetle. If it is really borers, can it kill the tree?

ANSWER: From what I can see I would say that the holes are from borers. The limbs should be dying?? Borers are associated with stress of the tree usually drought. Here is a web  link to information on the borer and management methods. The important thing would be keeping the trees drought free and healthy.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7425.html

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Eucalyptus Tree Foliag   QUESTION: I had the leaves tested last October and it was found out that the they had galls caused by wasps. The leaves also have spot fungus. And now they have borer insects as you identified the previous image sent. Does the presence of these pests make the tree hazardous? I attached the picture of the entire tree and could not really tell if the tree is declining or if it can still recover.

Answer
Borers can kill a tree if left untreated. I am not familiar with what type of insecticides might be available in New Zealand but here in the US we have an insecticide called Bayer Advanced Tree and Shrub Insect control. It is applied around the tree and the roots take the chemical to the trunk and branches and kill any insect feeding on the tree. It will also work for the gall insects. Gall insects do not cause mortality to a tree but the borers can. I would also fertilize the tree with a common fertilizer like 10-10-10. Use about  1 lb. of fertilizer per inch of trunk diameter scattered around the tree and watered in good. This will increase the overall health of the tree and reduce the stress it seems to be under now.

Here is a web link to the Bayer product. Check with a store that sells insecticide and fertilizer for this OR an insecticide for Borers on trees. Good luck!
http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect