GOLDEN APPLE SNAIL SITUATION AND INTEGRATED MANAGEMENT ACTIVITIES IN SOUTH VIET NAM Back

 

Nguyen Huu Huan1 and Ravindra C. Joshi2

1 Vice Director General, Department of Plant Protection, Ministry of Agriculture and Rural Development, Ho Chi Minh City, Viet Nam
2 Senior Research Fellow, Philippine Rice Research Institute (PhilRice), Maligaya, Muñoz Science City, Nueva Ecija 3119, Philippines
E-mail: ppdsouth@hcm.fpt.vn; rcjoshi@philrice.gov.ph; joshiraviph@yahoo.com

 

Introduction

The Golden Apple Snail (GAS), Pomacea canaliculata (Lamarck), is an important pest of irrigated rice in Viet Nam, especially on the direct-seeded rice in the Mekong Delta. Since 1988 some Vietnamese farmers introduced GAS from Taiwan and Philippines, because of its fast growth, high protein content, and good taste and ease of rearing. Two years later, there were 2 private entrepreneurs (one of them in Ho Chi Minh City and the other one in Kien Giang Province) engaged in large scale snail farming involved farm organizations to promote and sell GAS to other countries. Until 1993, through FAO office in Viet Nam, we were aware of the damage of GAS. The alarming state of GAS infestation became more vivid through out a workshop on the GAS management, which was organized in Tien Giang Province, South Vietnam. The Prime Minister of Vietnamese Government released Decree No. 528/TTg, date September 29, 1994 on GAS prevention, control programs and it was banned raising and transportation.

From September, 1994 to June, 1995 we assessed the distribution of GAS between rice and non-rice habitats and carried out control in whole country, we found out that it appeared in most of provinces. Total funds for GAS control were 2,079 million VND. GAS and its eggmasses destroyed were about 689 tons and 102 tons, respectively.

Today, the average rice area infested annually by GAS in the South Viet Nam is around 80,000 ha. This pest is difficult to control and it spreads everywhere even in the canals of communities.

This report presents information on status of GAS and the effective control measures in the South Viet Nam.


GAS Outbreaks in Recent Years

Based on the survey results made by Plant Protection Department in 1995, the GAS had been spread to all provinces in the whole country (61 / 61 provinces). Infested areas includes 22,717 ha of rice, 460 ha of water morning glory (Ipomoea aquatica) ponds and pools, and 1,147 km of community canals.

GAS is causing serious damage on rice, every rice-cropping season. Its attack force rice farmers to re-seed 2-3 times.

According to Matthias Halwart (1994) showed that the approximate distribution of the GAS in rice in the South Viet Nam first observed in1988.

In the past 5 years, there were 3 years (1999, 2000 and 2001) of widespread GAS outbreaks in South Viet Nam. The GAS population and the infested area (including rice and non-rice habitats) were usually much higher and larger than before 1999 (Table 1 & 2). The floods in the Mekong Delta probably explain this.

Although, the geographical distribution of the GAS is in all provinces in the south
of Viet Nam, but the provinces which grow rice with available irrigation suffer most from GAS damage. In many waterways in the southwestern part of Ho Chi Minh City GAS occurs much more abundantly and frequently than in other northeastern part.

On the other hand, the translocation movement of the GAS during flooding time
(July to October) from one province to another province is very clearly in the Mekong Delta.

 

Table 1. Infested Rice area by GAS in Past Five Years, South Viet Nam.

Year Infested Rice Area (ha)
1997 64,087
1998 36,079
1999 136,575
2000 99,356
2001 199,414
Total 435,511

 

Table 2. Volumes of GAS and its Eggmasses Caught in the Yearly Campaigns.

Year GAS (kg) Eggmasses (kg)
1997 125,853.3 4,139.5
1998 575,491.0 813.0
1999 24,940,436.2 263,893.3
2000 8,607,117.0 145,868.5
2001 6,955,614.9 19,414.2
total 41,204,539.4 434,128.5

 


Current Activities of GAS Management

Today, the GAS infestation in the South Viet Nam is known to public and private sectors. Thus, individuals acting alone cannot manage GAS through integrated management system. It is best if groups of farmers’ act together to help establish such a system to obtain stable yield or reduce cost of GAS control.

Generally, with funds coming from Government or local Government for basic research or extension; the technicians of Sub-Department of Plant Protection or Extension Agency in provincial levels do GAS management. Their efforts include research, farmer training by many methods such as “talk and chalk”, panels, leaflets, TV, radio, etc. On the other hand, leaders of local Government organize yearly campaigns on “community GAS control” by soldiers, students, and a large of farmers to reduce GAS populations in community waterways by handpicking method.


Results of Researches

Ecology

According to Kim Cuc (1991), the GAS has gills and a lung-like breathing organ.
Thus, it could life in wetland or upland habitat inspite of even low oxygen conditions (0.3 mg O2 per liter).

GAS is a botanical polyphagous animal; when female GAS grow up at 3 gram
weight (around 30 day-old) or more they can mate and lay eggs. The female GAS crawls out of the water level to lay eggmasses which are bright pink (each eggmass has 10-500 eggs). The female GAS once finished mating, separate out of male. After 8-10 days of mating the female lays eggs. It is possible that sperms of male can still alive in female body until 8-10 days after mating.

The increase in weight of GAS depends on the stages, water temperature, rearing conditions, food for feeding, fecundity etc. However, in the pond conditions the juvenile GAS (<1gr/GAS) and adults (5-10 gr./GAS) can increase weight at 0.035-0.065 gr./day/GAS and 0.330-0.700 gr./day/GAS, respectively.

Figure 1 showed that females reach maturity and took them into the productivity where at first 10 days an average number of egg masses around 3 per female with 3-4 day intervals/egg mass; most of egg masses were laid at the first month. There was decrease of number of egg masses after 30-90 days.


Attractiveness of some Botanical Leaves on GAS
(Source: Le Duc Dong, 1998).


Attractiveness of botanical leaves to GAS was replicated thrice and tested in ponds sized 350m2. In future, baiting with botanical leaves (Table 3) would help to trap GAS in community waterways and thus facilitate easy GAS collection and minimize environmental toxicity.

 

Table 3. Attractiveness capacity of some botanical leaves to GAS.

Raw materials Number of GAS caught in bait traps
1 DAT 2 DAT 3 DAT 4 DAT
Euphorbia leaves (Ricinus communis) 5.67a 6.33a 3.33a 2.67a
Papaya leaves (Carica papaya) 4.67a 5.00a 3.67a 2.00abc
Cassava leaves (Manihot utilissima) 4.33ab 5.00a 3.33a 2.33ab
Jack fruit filament (Artocarpus heterophyllus) 3.33b 2.33b 1.33b 1.33abc
Taro leaves (Colocasia macrorrhiza) 1.67c 3.00b 0.67b 0.67bc
Water convolvulus (Ipomoea aquatica) 1.67c 1.67b 0.33b 0.33c

Note:
Means followed by a common letter are not significantly different at the 5% level by DMRT.
DAT: Day after treated.

Effect of some pesticides on mortality of GAS.

Effect of some pesticides on mortality of GAS was carried out with 3 replications, using randomized complete block design (RCBD). Each plot measured 1m2 with 50 rice hills and 15 GAS (3.5-cm shell height). Bayluscide 250EC (niclosamide) at rate 0.12ml/m2 resulted over 99% mortality at 5, 7, 10 and 14 days after treatment application. Plots treated with Padan 95% WP at rate 0.12g/ m2 also exhibited high GAS mortality (>99%) at 10 and 14 days after treatment application. The remaining pesticides caused low levels of mortalities (Table 4).

 

Table 4. Effect of some pesticides on mortality of GAS.

Pesticide

Dosage

(gr.ml/m2)

Mortality(%)

3 DAT

5 DAT

7 DAT

10 DAT

14 DAT

Bayluscide

Padan

CaCO3

Meta 6%

Meta 5%

CuSO4

Control

0.12 ml

0.12g

65.0g

0.80g

0.20g

0.65g

Untreated

44.34a

21.68b

36.09ab

0.01c

0.00c

0.01c

0.00c

99.99a

55.57b

53.33b

23.61c

14.89c

0.00d

0.11d

99.99a

91.70b

58.01d

66.78c

24.37e

3.00f

0.00f

99.99a

99.12a

60.06c

88.670b

36.80d

36.00d

0.00e

100.0a

100.0a

62.43c

89.11b

48.87d

46.38d

0.00e

Note:
Means followed by a common letter are not significantly different at the 5% level by DMRT.
DAT: Day after treated.


Effect of some botanical pesticides on mortality of GAS.

Botanical pesticides were tested for their toxicity to GAS (Table 5). The Rotex 5%WP (Rotenone from Derris) (30kg/ha) resulted in 73% and 86% GAS mortalities at 5 and 7 days after treatment application, respectively. While the rest of treatments were less lethal to GAS.


Farmer Training & IPM

In order to guide the farmers manage GAS in the rice fields, plant protection network in Viet Nam in different locations yearly conduct “community IPM”. Current activities on the management of the GAS includes:


Difficulties/Limitations in GAS Management


References

 

 

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