Sunday, January 20, 2013

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, Tamilnadu on May, 2012, I pointed out the same deformity of apical tip in some Melia dubia trees  (2 %to 3%) in their demo plots also that had not been observed by them earlier. The photos I had with me at that time were not good (long shots) so requested the FCRI people to take close up shots since they have a very high portable aluminum ladder to reach the tree tops easily. I fervently hoped that with all the correct persons, knowledge, equipment and lab, FCRI can find the reason and suggest a remedy which will definitely benefit poor ‘Melia tree grower’. After continuous follow up I came to know that exact cause of this condition is still not identifiable and they are also receiving same complaints from many Melia fields in T.N.
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.

May be this deformity is due to physiological or environmental factors also. I kindly request our knowledgeable readers and ‘Melia growers’ to come out with their view. May be some of you might have invented cure for this infection. Speak out !, since you are the correct person to judge the cause and suggest remedy for this mysterious ‘Apical shoot deformity in Melia dubia’.


A.Vishnu Sankar

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