Page 98 - Tài liệu Ebook cây cảnh Bonsai Basics

100 HEALTHY BONSAI

With most fungal control, prevention through a flame). The only effective way
is better than cure. For instance, of controlling canker is to cut out in-
although powdery mildew is treated by fected areas - cutting away a branch or
simple methods, it can be very persistent. removing infected tissue. Be careful to
Therefore start treating potential mil- dress the wounds made in this way with
dew victims before the mildew appears. mastic to help them heal and to exclude
further infection. It is vital to burn all
diseased wood immediately and to steril-
Root rot ize the tools you have used.
This serious fungal disease affects only
the roots. It is most often caused by
contamination from poorly decomposed Viral diseases
organic fertilizer used straight on the These are, fortunately, seldom encoun-
roots (fresh manure, for example). The tered, for one can only control this
fungus is encouraged by over generous trouble by destroying infected plants to
watering, poor drainage and by standing stop the disease spreading to other
the contai,ner on a tray or saucer. plants and becoming an epidemic.
As root rot affects the underground The most dangerous viral disease of
part of the plant, it is difficult to treat. If cultivated plants is without doubt mo-
you are worried, you should examine the saic, which appears as a mottling -
roots carefully when lifting or repotting alternate green and yellow stripes or
the bonsai. It is hard to combat root rot. other shaped areas - on the leaves, and
The best way is to remove all infected by a highlighting of the leaf veins. The
roots, which could itself have grave leaves eventually shrivel, dry up and fall.
consequences for the bonsai, as the
imbalance between roots and top growth
could kill it. Lift the plant and brush Control materials
away all contaminated soil as quickly as The chemical products used to control
possible. After transplanting in fresh these diseases are offered either as
compost, spray the foliage well to com- dilutable liquids (or powders to be dis-
pensate for the water the plant roots are solved in water), or as powders to be
unable to provide. used in that form . So you need a sprayer
and a powder blower as well.
The sprayer is also valuable for damp-
Canker ing over the plants' foliage as necessary,
This is a bacterial rather than a fungal so it is an indispensable item of equip-
disease, which shows as swelling of the ment. A powder blower, on the other
bark and callosities. It often arises after hand, is used less frequently, and only in
pruning with tools that have not been special situations. What is more, some
sterilized after cutting infected material products which are offered in powder
(which shows the wisdom of passing the form can only be used when conditions
blades of a grafting knife or secateurs are right for dusting.