New Zealand Treecrops Association

Research - Canker

Cypress suffer from Boron deficiency?

I have been reluctant to go to print on this one because I thought it was too good to be true, but for the past 2 to 3 years I have seen a significant decrease in canker problems within a cypress stand that has been treated with adequate amounts of boron.

As I have previously mentioned, all trees need the trace element boron, particularly pine. This species is more vulnerable to boron deficiency, though all conifer benefit from an application of boron i.e. Douglas fir, and the cypress species.

In my opinion, boron not only reduces the effect of canker but also helps to eliminate it. As long as boron levels in the foliage do not fall below 20 ppm, cypress which are boron rich appear to have a resistance to canker infestation. Even when canker is present, a boron application stops the infection travelling up the tree. I know this sounds a bit far fetched but I likened canker to a cancerous growth. Once the tree is effected it is better removed from the stand because the wood quality will be extremely poor, and the canker gradually increases in size until it kills the tree.

In the old days pruners were dipped in fungicide to stop canker going in through the pruned stumps; it was a real threat when 20-30% of trees showed symptoms of canker. It appeared to attack vulnerable trees which were weak due to weather or other reasons. If a tree was healthy it was resistant to canker.

I have no hesitation in recommending boron application to a cypress stand knowing the tree health will benefit, but ideally I should wait a couple more years before I can guarantee that a boron rich tree is not only more resistant to canker, but also can be cured of this cancerous growth.

But this may be too late for some people, so, if you are growing cypress, seriously consider a boron application especially if the trees will be under stress from intensive pruning because the canker enters through the pruned stubs. If the tree is not healthy the sap flow is non existent. We have found that boron rich trees have an increased sap flow.

From NZTCA Aoraki Branch newsletter, July 2002.

http://www.treecrops.org.nz/research/canker/cypress.html
Created: Wednesday, 30 July 2003 - Modified: 2008 July 11