Lilac borer

[Your Letters 2]

Is there any way I can save my white lilac ( it has borer)? It's 20 years old.

- G. C. -

[Janet Macunovich 32]

Lilacs are born to survive! Yours will. You and a pruning saw can help it along.

 

Cut the borer-inhabited stems now - every cane bigger around than a shovel handle, cut it off at ground level. Then get all that wood out of the yard or burn it so the borer caterpillars inside cannot emerge, turn into borer moths and lay eggs on some other lilac to start all over.

 

Cut now! Those borers are about to emerge.

 

 

The borers need decent-sized wood to have enough cambium to sustain them, once they gnaw their way in. So there will not be enough sustenance in the young shoots that are there now or will sprout from your cut-down roots and stem base. New canes won't bloom for two or three years and after that they will have another 2 or 3 years of being small enough in diameter to be pretty safe from borers.

 

If a lilac is pruned regularly to renew the wood - that means taking an old cane or two out every year, right to the ground - and you let new replacement shoots come up, it will stay ahead of borers. So cut yours all the way back now -- all the canes that are bigger in diameter than a shovel handle - and mark your calendar for 2 years from now to begin taking a shovel-handle-sized cane or two out every year. Those you do not cut will bloom and the borer-free life the shrub has been leading can continue.