Insect Pests – Rhizome Weevil / Corm borer

Insect Pests – Rhizome Weevil / Corm borer:

Symptoms:

Adult weevil (Cosmopolites sordidus) is black and mostly found in between leaf sheaths and in the soil at the base of the rhizome. Rhizome weevil interfere with the root initiation, kill existing roots that limits nutrient uptake, reduces plant vigour, delays flowering and increases susceptibility to other pests and diseases.

Larvae of the weevil furrow into the rhizome at different locations creating a network of hollow tunnels which are not visible externally. Larvae sometimes bore into the pseudostem also. 
Infestation at the early stage reduces plant vigour. Sick appearance and yellow lines on the top leaves are early symptoms.

In the advanced stage of infestation, plant shows tapering of stem at crown region, reduction in the leaf size, poor bunch formation and choked throat appearance due to grub damage in the corms. Attacked rhizome and pseudostem gets girdled with holes that result into toppling of the plants. The weevil spreads through infested suckers to different places.

Rhizome weevil / Corm borer affected plant

Rhizome weevil / Corm borer affected corm

Rhizome weevil / Corm borer affected suckers and corm

Usage of Pseudostem injector to control Rhizome weevil / Corm borer

Control:

1. Keep the plantation clean without weeds, remove trashes and burn the refuse. 
2. You can be rest assured of infection free planting material if you go for ‘Tissue culture plants. Avoid planting of borer infested suckers. To make sure that you have clean suckers, the roots should be trimmed and pared-off all tissues on the surface to make it free of any infestations and dip the pared corm in a solution containing 0.5% Monocrotophos or Trizophos 2.5 ml in 1 litre solution for 30 minutes. Alternatively application of 40g of Carbofuran in the soil at planting can also be followed. 
3.  Dilute Monocrotophos 150 ml in  350 ml of water and inject 4 ml in the rhizome using Pseudostem injector in a 45 degree slanting angle. For more details click this link: A novel method for effective control of Weevil attacks in Banana plants. 
4. Rake the soil around the rhizome and apply through drenching 2 gm / litre Carbaryl or 0.03% Chlorpyriphos or 10 g / plant Carbofuran 3G or 10 gram / plant Phorate 10G two times at 10 days interval followed by tight watering.

Regards,
A.Vishnu Sankar