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Countermeasures Suggested Against Acacia mangium Seedling Damage

Despite a week-long field investigation by forestry experts from Hanoi, the causes of unusual Acacia mangium seedling damage that occurred in the project pilot site (Ta Leng Site) in 2012 are still largely unknown, but several recommendations have been made for successful afforestation in 2013.

The Damage Begun

In the summer of 2012, the project supported tree planting in five villages in its pilot sites in Dien Bien Phu City, Dien Bien District, and Dien Bien Dong District with provision of around 193,000 A. mangium seedlings. The planting was preceded by a simple training course on tree planting techniques for the villagers. However, after the planting, the villagers claimed that many of the A. mangium seedlings were damaged, provably by grasshoppers, particularly in two villages, namely Na Nghe and Ke Nenh in Dien Bien Phu City. According to the local authority, the damage on A. mangium seedlings was "not very common" in the past although it was occasionally observed in the province.

The Initial Investigation by the City Authority

Immediately after the damage was reported, on 1 August 2012, the Dien Bien Phu City People's Committee invited specialists from several local organizations to observe the sites and investigate the causes of the damage. Although these specialists could suggest various possible reasons, they could not identify neither conclusive evidences nor practical countermeasures at that time. As a result, they could only agree on the replacement of dead seedlings with another species (Manglietia sp.).

However, the damage was continuously reported in the other village (Phieng Bua) in Ta Leng Site in Dien Bien Phu City. The project thus commissioned an investigative study on A. mangium seedling damage in the pilot site to a group of scientists from the Vietnam Academy of Forest Science (VAFS) in Hanoi in October 2012.

The Investigation by VAFS

A total of 58 households in four sample villages, including the three villages mentioned earlier and Phieng Ban Village in Dien Bien District (that had not experienced serious damage to their seedlings), 14 stakeholders, and 114 sample plots (100m2 each) were interviewed or surveyed during the a week-long field investigation for in mid October 2012. The result of the sample plot shows that 55.9% of the planted seedlings had been dead while 37.6% of the seedlings had been survived by the time of the survey in Ta Leng Site. This result is quite contrasting with that of Phieng Ban that recorded around 70.1% survival rate although 25.6% still experienced death.

As for the reasons for the seedlings' death in the three villages in Dien Bien Phu City, the sample plot survey could not conclude on the causes of such for most (92.2%) of the seedlings due to the late organization of the field survey (i.e., little evidence remaining in the field). However, remaining evidences show that the damage or death might have come from rats (4.4%), grasshoppers (1.0%), humans (0.9%), termites (0.8%), and others.

The interview results with village households present a little contrasting picture of the causes. Among the interviewed households in the same three villages, crickets were the most commonly mentioned reason (32.4%), seconded by termites (30.4%). Other claimed reasons for the damage/death were grasshoppers (27.1%), rats (26.8%), cattle (5.0%), and humans (2.5%).

Although the study was not conclusive on the causes of the seedling damage or death, the report came up with a set of recommendations including direct control such as application of chemicals and indirect control including better selection of planting tree species (with due consideration to the altitude), improved weeding, capacity building of participant households, supplementary planting, and adoption of planting schedule against reproduction cycle of these insects.

Based on these recommendations and through the discussion with the government counterparts in the provincial, district and commune levels, the project is planning to undertake the tree planting earlier with larger seedlings in 2013.


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