Apical shoot deformity in Melia dubia (Malai Vembu, Konda Vepa, Hebbevu) plantations:
Dear Friends,
Melia dubia (Malai Vembu, Konda Vepa,
Hebbevu) is now in lime light only because of its tremendous initial growth
i.e., during first two years even in marginal soils with sparse irrigation. Its
growth after that initial period vastly differs from field to field and the
current field reports are not that much encouraging in many parts of Tamilnadu,
Andhra and Karnataka states.
Growth variation is so huge that even in
my field, girth increment of some 4 year old trees are 200% more than 8 year
old trees. Since too much hype has been generated already, reality will sink in
slowly and in the coming years farmers will come to know about
the type of soil required, soil depth, climate, tolerance to maximum
temperature, drought tolerance and water requirement for successful cultivation
of Melia dubia.
Though drought tolerance of this tree is
moderate, it becomes ‘stunted’ during prolonged droughts. Tree will shed all
its leaves and the growth stops during extreme and prolonged hot conditions. Do
not plant in Alkaline soil, clay, sodic soils and wherever there is poor soil
depth. Melia grows well in irrigated (weekly once) soils where pH is below 7.5.
All the plants in a field will not grow
uniformly and the trees planted in bunds and near water channels exhibits rapid
growth and attain enormous girth within 4 - 5 years. The presence of this
kind of + trees though in small percentage are brought to centre stage by
ruthless traders to make quick money. The pictures and Videos of young yet
enormous Melia trees you find in 'Net' are carefully selected picks from the
above +trees among a vast lot of average plants. So, don’t get distracted and
be realistic in your estimates as the law of averages will always come to play
even in your field.
‘Apical shoot deformity in Melia dubia’:
I happened to notice in my field last
year that apical tip (actively growing top most tip of a plant) of about 5% to 8%
of my Melia trees were found to be deformed. On closer examination I could not
able to see any pest infestation (bore hole) leading to canker or any fungal
infestation. In the later months I happened to see the same mysterious
deformity in many parts of Tamilnadu and Karnataka states. I showed this
condition to CCF and ACCFs of Forest Extension Department in their own demo
plots itself in various districts.
The affected tree exhibits no vertical
growth and for identification purpose I named it as ‘Apical shoot deformity in Melia dubia’. The affected plant part is
usually about 1.5 to 2 feet, swollen, black in colour, rigid, one third of the
length curved like a sickle or coiled. A tree planted
in my backyard first showed this deformity about 2 years back. Now, the growing
tip of lower most side branch of the same tree is also got affected.
Picture of deformity in side branch:
At the time of my visit to Forest
College Research Institute (FCRI), Mettupalayam, Coimbatore
Then I happened to hear from few scientists
of Institute of Forest Genetics and Tree Breeding Institute (IFGTB), Coimbatore
that they have also observed this when they visited some pest infested Melia fields (Melia plantations affected by ‘Stem borers’ and ‘root grubs’) for on the spot
assessment. According to them the scale of ‘Apical shoot deformity’ is up to 10%
in some fields and their initial studies have revealed that this attack is neither
due to insect nor due to fungus. Lab tests were going on to assess whether this
is a viral infection since severely infected plots are located adjacent to fields
with gourd family (Cucurbitaceae) vegetables which are a major source of virus
pathogens.
Let these research institutions come
with their findings at their leisure. We can not blame them since they don’t
have virus testing facilities in their labs and even If they identify the cause
for this deformity it has to be proved scientifically, has to be documented, corroborated
by senior scientists before press release.
Regards,
A.Vishnu Sankar
