Stem borer attack in Melia dubia (Malai vembu)

Dear friends,
A keen follower of this blog has sent the following queries and pictures for clarification.

Question:

I have planted around 600 Malai Vembu in my agriculture land in Salem @ a spacing of 10 feet x 10 feet. The trees are about 8 month old, drip irrigated and have attained a height of about 10 to 12 feet. I am facing two problems now. There is bulging of stem in some plants and the earlier occurred plants broke subsequently. This bulging of stem occurs at various heights of the plant. Is it Stem borer ('Thandu Puzhu' in Tamil)? Whether Phorate application controls it?

Secondly I notice branches shooting out and in some trees they fall down on their own on reaching a length of 3 to 4 feet. Shall I allow these branches to grow? Please suggest me solutions for these.

Answer: The above pictures were sent to Dr.K.K.Suresh, Prof & Head, Dept. of Forestry and Silviculture, Forest College and Research Institute, Mettupalayam, and Mr.Sivakumar, Senior Scientist, IFGTB, Coimbatore for their opinion. Replies received:

• It looks like stem borer. You may make your observation in the point of breaking of stem for any bore hole for confirming the presence of stem borer.


• The treatment recommended for Casuarina stem borer attack may be followed. Inserting wire through the bore hole to remove the feeding larvae and applying insecticide soaked cotton (15ml of dichlorvos). Injecting insecticide into the holes where the larvae puss out their frass is the effective method. Inject after removal of frass.


• Application of Phorate in the soil may not be appropriate at this chronic stage. Since the pest is a borer, application of phorate in the soil around the stem disrupts its life cycle and multiplication.


• For clear examination, send cut portion of the infected region through courier for a clear examination and for recommending the right control measure.


• Once the stem break you will notice new shoots coming out just below the broken portion. You have to cut the tree at the base and allow the coppice shoot at the base to come up (See the picture below) and not the shoot at the top (near the broken point), as this may dislodge if there is heavy wind.

• Breaking of branches may also be due to attack by some insects as this tree does not shed branches of its own as done in Eucalyptus.

• Remove and burn all broken branches in which the breeding takes place.


• If the pest attack exceeds the threshold limit, spraying of 0.2% dichlorvos with 0.2% Chlorpyrifos or Monocrotophos as foliar application followed by soil application of 20 gm of Phorate or Carbofuran per plant will give desired result.

My sincere and heartfelt thanks on behalf of all the readers to the above two scientists for giving this detailed reply.

Regards,
Vishnu Sankar.