Thursday, March 27, 2008

ISA HK/Chia --- Introduction to IPM (Part 3 & 4)

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Dear Station Members,

Further to the issue of the Part 1 & 2 of the same article a few weeks ago, please kindly find the remaining Part 3 & 4 in consecutive Station Mail to complete this series.

The attached article advised upon how to implement IPM together with PHC. After all, what's good is it to know the benefits of IPM but not knowing how to apply? Arboriculture is a Practitioner Trade & Arborists are front-line professionals solving problems on the spot. It is therefore important for them to understand how to deal with practical situation at all time.

Many trees in our territory actually developed symptoms from poor nursery stock selection & incorrect cultural practice without the landscapers really knowing why. For example, China stocks are usually planted very close together like sugar canes with trunks shaded from canopies during production. When a selected tree is pulled out from the crowd, the trunk without Taper which has been protected from sunlight all the time would be suddenly exposed to light & wind. Many would develop sunscald in this manner which would lead to cracks & then wounds; & to cavities & eventually decay. With decay in trunk & branches, there is always a chance for failure in the wind.

Another major challenge for China stocks is that they would usually come with undersized rootballs. An internationally acceptable rootball would be at least 10 times the size of the trunk diameter, i.e. a 3 inch trunk would come with a 30 inch rootball. This is to ensure that the transplanted tree could retain adequate roots to carry on the normal functions demanded by a tree. Without enough roots, the tree would go into ' Transplant Shock', & would sit there suffering or dying, defeating the purpose of installing a tree in landscape. Yet tree arrival on site is rarely inspected on the spot before installation in our territory. Post planting inspection is usually carried out, but this will be too late to spot for anything especially rootball size. The tree would then develop symptom of one or the other later on without anybody knowing why.

Other common defects associated with China stocks would be Girdling Roots due to production in containers, & incorrect pruning such as Topping which produces large wound & destroys Tree Structure. A lot of trees are also installed with added fertilizers in the backfill which would burn off the emerging roots to impede recovery. Symptoms would eventually appear.

The combination of poor nursery stocks & incorrect cultural practices is actually harming our trees. Sophistication in chemical spray appears to be the depended solution in our territory. Some tend to think that the better we spray, the better trees we'll get.

Then does it work out this way?

Please try to find the answers in the attached article.

best regards,

Sammy Au
Station Manager

The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (