Iodine Staining Test

The new BS3998:2010 Tree Work – Recommendations makes an interesting reference to Starch Testing (page 19, section 7.2.1) which I’m sure may flummox many practicing Arborists.

An Iodine Stain can be used to assess the energy levels of a tree and should, in the first instance, be a simple field test. The test ascertains the concentration of starch in a sample from the last three sapwood increments taken from small cores representative of the whole tree.

Trees require energy for all functions, including respiration and reproduction of cells, growing new tissues, and maintaining defences against invading insects and disease. Some of this energy comes directly from the leaves, as it is made. The rest comes from the stored reserves.

During the growing season, the tree manufactures sugars and carbohydrates in the foliage. These compounds contain the energy needed for metabolism. Whatever is not used for current needs in the tree is transported to the woody tissues and converted to starches for storage in the living cells of the branch, trunk, and root wood. The amount of available stored energy within the tree is an indication of the vigour of that tree, and its general health.

The starch content of the tree will help guide the Arborist as to the level of pruning any particular tree will tolerate.

There are some limitations to the testing including species and site specific discrepancies however the test could prove a useful tool and should perhaps become a common precursor to prescribing tree surgery operations.

We are currently evaluating the practicalities of the test for field use and are planning to offer a workshop in the not too distant future to raise of awareness of the process and hopefully encourage its use amongst tree surgeons/tree care professionals.

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