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

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Posted in: Insect Pests – Rhizome Weevil / Corm borer

Insect Pests – Pseudostem Weevil / Borer

Insect Pests – Pseudostem Weevil / Borer:

Symptoms:

The Pseudostem weevil (Odoiporus longicollis) are normally black coloured ones but red coloured variants are also found in some areas. The pest breeds and become more active during summer and monsoon seasons.

Early symptoms of infestation are the presence of small pin-head sized holes on the pseudostem, fibrous extrusions from bases of the leaf petioles and exudation of a gummy substance from the holes of the pseudostem.

The weevil larvae are fleshy and yellowish white. Larva bores hole through the pseudostem and thrives inside. This results in exudation of plant sap followed by dropping of the faecal matter. As the central core is destroyed due to the boring of the larvae, upward movement of the nutrient is hampered which ultimately results in poor growth and development of the plants.

If the larva tunnels pseudostem during advanced pre-flowering stage, the ascending flower bud and peduncles are destroyed resulting in non emergence of the flower bud which decays inside the pseudostem. This leads to choked throat appearance of bunch and breaking of Pseudostem.

During advanced stages of infestation, we can observe by splitting the stem, the pests' extensive tunneling both in the leaf sheath and in the rhizome. Rotting occurs due to secondary infection of other pathogens and foul odour is emitted. When the rhizome and peduncle are tunnelled after flowering, the fruits do not develop properly, exhibiting a dehydrated condition with premature ripening of the bunch.

Pseudostem weevil affected plant with immature bunch

Pseudostem weevils / grubs

Pseudostem weevil attack - Bore hole on Banana

 Control:  

1. Keep the plantation clean.  
2. Remove trashes and burn the refuse. 
3. Do not dump infected plant into manure pit. 
4. Uproot infected trees, chop into pieces and burn. 
5. You can be rest assured of infection free planting material if you go for ‘Tissue culture plants. If you opt for suckers, then 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 2.5 ml in 1 litre solution of Trizophos for 30 minutes. Alternatively application of 40g of Carbofuran in the soil at planting can also be followed. 
6. Do not plant susceptible varieties in the endemic areas such as Nendran, Mondan, Ney poovan etc. 
7. Dilute Monocrotophos 150 ml in  350 ml of water and inject 4 ml in the pseudostem about 2 feet higher from the ground (preferably below bore hole) using Pseudostem injector in a 45 degree slanting angle. For more details click this link: A novel method for effective control of Pseudostem weevil using Pseudostem Injector. 
8. Rake the soil around the pseudostem and apply 0.1% Metasystox or 0.05% Quinalphos or 0.03% Chlorpyriphos or 0.2% Carbaryl followed by light irrigation, at 15 days interval.  
9. Method to trap the weevil with spilt pseudostem: The freshly cut pseudostem is a good breeding place for weevils. So, after the bunch has been harvested, cut the pseudostem close to the ground then cut it into small pieces in lengths of up to 60 cm, split each along its length and place them in the soil in the way that the cut portion faces the ground. These cut pieces (split traps) attract adult female weevils to feed and lay their eggs. As soon as the larvae emerge, these pieces become dry and eventually the larvae die because of dehydration. This split trap method to trap the weevil is just to monitor the extent of infection in the field and control measures have to be taken up immediately.
10. The open cut side of the above pseudostem cut pieces about 30 to 40 numbers (split traps) can be sprayed with 0.5% solution of Beauveria bassiana or  Metarhizium anisopliae,  both are entomopathogenic bio control agents before placing them face down on the soil. The weevil gets infected by the fungal conidia (spores) when it enters the pseudostem trap. It is enough for the conidia of the fungus to come in to contact with the body of the weevil or ingested where it grow and colonize the host body. Then they germinate and the hyphae that emerge penetrate the cuticle of the insect host. After extensive invasion of the host body, the Destruxins produced by the fungus eventually weaken and kill the insects within 72 hours.
11. Use Pheromone traps (2 traps/acre) and destroy the collected weevils. 

A Pseudostem Injector and a Pseudostem cut piece for weevil trap

Regards,
A.Vishnu Sankar

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Posted in: Insect Pests – Pseudostem Weevil / Borer

Fungal Disease (Pre & Post Harvest): Fruit Freckle / Leaf Freckle

Fungal Disease (Pre & Post Harvest):
Fruit Freckle & Leaf Freckle: 

Symptoms:

Causal organism of this disease is a fungus which has two names, Phyllostictina  musarum and Guignardia musae because the fungus produces two types of spores causing brown to black coloured small and large spots on the leaves and fruits.

These spots can run together to form streaks. Severe infection results in yellowing followed by withering and ultimately death of the leaves.

The most characteristic symptom of both types of spots is a sand paper feel of the leaf and fruit surface. The fungus normally grows on the dead hanging leaves and spreads to fingers during rainy and windy weather.

 

Freckle disease on banana leaf

Freckle disease on banana fruit

Control:

• Removal infected and dried leaves at regular intervals. 
•  Spray at weekly interval once or twice or dip the unripe harvested fruits in 0.05% Bavistin or 0.25% Mancozeb. 
•  Using Polythene bunch cover is found to be effective.

Regards,
A.Vishnu Sankar

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Posted in: 50. Fungal Disease - Fruit Freckle / Leaf Freckle

Fungal Disease (Pre & Post Harvest) – Speckle

Fungal Disease (Pre & Post Harvest) – Speckle:

Symptoms: 

Fungus Deightoniella torulosa causes 'Speckle disease' and the symptoms are minute reddish brown black spots surrounded by a green halo which develops at all stages of fruit maturity. The spots are 2 mm in diameter but may reach up to 4 mm as the fruit approaches harvesting. The fungus normally grows on the dead hanging leaves and spreads to fingers during rainy and windy weather.

Speckle disease in Banana - Initial stage on green leaf

Speckle disease in Banana - Mature stage on dead hanging leaf

Speckle disease on Banana fruit

    Control:  

• Removal of decaying leaf trash including transition leaves and bracts at regular intervals especially during rainy season. 
• Spray 0.05% Bavistin or 0.25% Kavach on weekly basis till bunch emergence and sleeving. 
•  Using Polythene bunch cover is found to be effective.

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Posted in: 53. Fungal Disease – Speckle

Fungal Disease (Pre & Post Harvest) – Brown spot or Diamond Spot:

Fungal Disease (Pre & Post Harvest) – Brown spot or Diamond Spot:

Symptoms:

The disease is caused by Cercospora hayi often in conjunction with Fusarium spp. These fungi are common saprophyte (fungal organisms which obtain nutrients from dead organic matter) on banana leaf trash and on senescent (aged, from full maturity phase to death) weed leaves. Spores are produced on the dead leaves and are released onto fruits even at very low wind velocities.

Cercospora hayi causes black, sunken, diamond shaped lesions on the harvesting grade fruits.  Inconspicuous spots may become prominent lesions during shipping and ripening. The first symptom caused by this fungus is slightly raised yellow spots, 3 – 5 mm in diameter on the green peel.  Fusarium sp. and Cercospora hayi inoculated together extend the initial yellow lesions into the typical diamond shape lesions. The infected cells fail to expand as the fruit grows and a longitudinal crack surrounded by a yellow halo develops resembling a diamond shaped lesion.

Brown spot or Diamond Spot disease in Banana fruit

 Control:

• Regular removal of drying and decaying leaves including bracts especially during rainy season. 
•  Using Polythene bunch cover is found to be effective. 
• Spray or dip the raw or harvested hands with 0.05% Bavistin or 0.01% Tilt or 0.25% Indofil M45 at 15 days interval.

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Posted in: 51. Fungal Disease – Brown spot or Diamond Spot

Fungal Disease (Pre & Post Harvest): Pitting Disease

Fungal Disease (Pre & Post Harvest) – Pitting Disease:

Symptoms:

The disease is caused by Pyricularia grisea and this is characterized by round, sunken pits of approximately 4 – 6 mm in diameter on the fruits after harvest or as the fruit reaches maturity. The sunken centre is surrounded by a reddish brown zone with a greenish, narrow, water soaked halo. Smaller pits occur on the finger stalks and crown pads which can lead to finger drop. Although the pit centres sometimes split, the damage is confined to the peel and does not extend to the pulp.

Symptoms are identical with those of ‘Johnston fruit-spot’ disease and are rarely seen in the field until 70 days after bunch emergence. . The extent of pitting may increase considerably while fruit is in transit and during ripening causing serious losses in the quality of fruits.

The main sources of inoculam for pitting disease are conidia produced on hanging banana leaf trash. Conidia are most abundant during rainy season and are wind dispersed onto the fruits. The fruit on the side of the bunch facing away from the pseudostem is more severely affected than fruit facing towards the pseudostem.

Pitting disease in banana fruit

Control: 

•  Regularly remove dried and decaying leaves hanging around the pseudostem. 
• Using Polythene bunch cover is found to be effective. 
•  Spray affected unripe fruit bunches or dip harvested hands with  Bavistin @ 1 gm / 1 litre at 15 days interval.

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Posted in: 52. Fungal Disease – Pitting Disease