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Last Update: 22 Jan 2018
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Jln. Tun Abdul Rahman Yakub, Petra Jaya, 93050 Kuching, Sarawak
Tel. No.: 082-441000   Fax No.: 082-447821
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For more enquiries, please contact us:

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Department of Agriculture Sarawak, 7th, 12-14, 16-17th Floor, Menara Pelita, Jln. Tun Abdul Rahman Yakub, Petra Jaya, 93050 Kuching, Sarawak

Tel. No.:  082-441000  
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Managing The Treat of The Apple SnailManaging The Treat of The Apple Snail
MANAGING THE THREAT OF THE APPLE SNAIL

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>> Snails feeding on rice leaf

 

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>> Life Cycle of The Apple Snails

INTRODUCTION
 

The apple snail are here to stay in Sarawak. It is therefore important to prevent any further spread and to learn how to live with them.

The widespread distributionof the snails was mainly through people bringing them into uninfested area for food. This is so because they were also found in oil palm estates and logging camps. This means that they have been brought into the State by some one for rearing in ponds for food.

The presence of the snails must be detected very early so that when their numbers are still small, total eradication can be carried out. Total eradication is the only measure to prevent any further spread or new incursion. This is because the presence of a single female can be disastrous as it can produce up to one million offspring in a year.

The maximum size with which you can possibly do total eradication is one hectare. However if the snails are already in the river system, total eradication may prove futile because you may not be able to find and destroy all of them in the water bodies. Also the snails can hide in dry places by burrowing deep under the earth surface.

AN INTERGRATED APPROACH IN MANAGING THE APPLE SNAIL

Once the apple snails are known to be already present the main objective in the management of the apple snails is to reduce the population so that the damage done to the rice seedlings are within tolerate limit.

The best approach is adopting the IPM (Integrated Pest Management) package which includes the following:

A. Cultural
B. Biological and
C. Chemical Control
A. Cultural Control
A1. Manual picking of snail

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>> Collect and destroy the eggs


Manual picking of adult snails and the eggs should be carried out as frequent as possible. For eggs it is a must because each egg mass contains about 500 eggs. Hence it is critical to collect the eggs once they are seen. As for the adult snails their numbers must be reduced as much as possible prior to planting the rice seedlings.

To ease the collection of the snails, placed baits such as leaves of papaya, tapioca and gliricidia. After 24 hours pick up the snails and destroy them.

A2. Rotovating the rice field
This is recommended for dry field. By rotovating, the snails will be exposed to the sun and die. Also some snails will be crushed. This is particularly suitable if a farm tractor or mini power tiller or a buffalo is available.
A3. Keep field dry
By keeping the field dry all the time after harvesting, the snail will not be able to lay eggs and breed.
A4. Use collecting trap


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>> Laying Trap


Traps are made of wire mesh of size 2 mm or less. Traditional bamboo traps can also be used. Place traps strategically to prevent the movement of snails from one field to the other. Inspect traps twice or at least once a day to prevent blockages.
A5. Prevent movement of machinery and animal
This is especially important when the amchinery or animal has gone through infested field. If they have to go to another field which is still free from snails, then they must be thoroughly cleaned. Inspect thoroughly that they do not harbor any snails or eggs.
A6. Use older seedlings and control water depth

Use 30 or 40 days old seedlings for transplanting.

For 30 days old seedlings the water depth must be maintainedb at 1 inch for 3 weeks. At this depth the adult snails do not move actively. After this water level can be raised to 2 inches.

For 40 days old seedlings the water depth can be maintained at 2 inches because at this age the tougher leave blades are not attractive for the snails to eat.

At bunting stage the water depth can be raisedf to 4 inches or more as the old leaves are no more attractive.

B. Biological Control

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>> Biological Control Using Ducks

Use ducks at a stocking rate of 5-10 ducks per hectare. The recommended duck breeds are William Siam, Taiwan, Mallard, Peking, Khaki Campbell and Muscovy. In Sarawak the Peking and the Muscovy breed are easily available.

Suitable time to use the ducks are:

  • During Off Season.
  • During land preparation and when water is introduced into the field.
  • 4 weeks after transplanting or 6 weeks after direct seedlings. This is to prevent the damage of the seedlings by the ducks.

Avoid releasing the ducks when seedlings have just been planted or during ripening of the grains.

C. Chemical Control

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>> Dead snails after chemical control


Chemical control is used when the population is too high and there is not enough labour to collect the snails manually. Use tea seed powder or metaldehyde 5 %.
C1. Tea Seed Powder

Use when the population of the snail reaches 5 snails per metre square and labour is not enough to do cultural control. Introduce water to the entire padi field for a few days to induce the snails hiding underground to surface. Ensure that the water depth is at least 2 inches and that the water does not move freely when the powder ia applied.

The powder is effective for up to 4 days; afterwhich rice planting can commence. The recommended rate is 51 kg/ha.

C2. Metaldeyde 5%

This can be used as an alternative especially for remote areas where logistics is a problem. Apply this snail pellet at 15 kg/ha; planting can commence 2 days later. The pellet is applied to pools or standing water soon after draining water away from the field.

Note: Bayluscide at 315gm/180 litres of water applied over one hectare of ricefield can be applied provided there is no concern over the death of fishes in the padifield or the waterways connected to the padifield. It is used for quick knockdown of snails in a newly discovered infested ares; provided the area is small (perhaps less than one hectare)

 
MANAGING THE THREAT
 
It is most important to bear in mind the measures one should undertake to manage the threat of the apple snails. In areas where wet rice are planted, farmers or growers should take serious note of what to do when the snails are not present and when snails are already present.

3.1 For uninfested area

Ensure no machinery or live animal such as buffalo from snail infested areas moves into snails free areas. Ensure that they are free of snails or eggs if they have to enter.

Inspect all water bodies such as drain, stream, rivers, puddles, etc for any sign of snails soon after flooding has occured.

Organize awareness program on the dangers of the snails and how to recognize them and also to emphasize the need to report immediately so that eradication measures can be done as soon as possible.

Distribute leaflets, poster, etc. Place posters in strategic areas or location; particularly where wet padi are grown.

3.2 For infested area

Managing the snails once they are already present must be done with the main objective of reducing the population especially prior to planting time. This must be done using the integrated approach as explained above. As far as possible adopt the cultural and biological methods before resorting to the use of chemicals.

CONCLUSION

The apple snail is a serious pest of rice and it poses a very serious threat to the livelihood of the rice growers. The main reason is that once snail are introduced into a new area it can establish and spread extremely fast.

An adult female can start laying eggs at just two months old. Each time it can lay up to 500 eggs. In the absence of many natural enemies, it is no wonder that a female can produce up to 1,000,000 offspring in a year.

When the field condition is dry the snails can hide underground for up to 8 months and resurface once the field is filled up with water.

The snail lays very distinct pink egg masses on any plant parts, stick-uprights, bridges etc. above the water surface. Rice growers must make the habit of picking-up and destroying the egg masses so as to effectively reduce the population.

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Source: Crop Protection Branch