Latest Pest and Diseases at Forest Plantation in Sarawak

Industrial Tree Plantation (ITP) is an intensively managed, even-age monoculture plantation, with special emphasis on fast-growing exotic species. For the State, this means Acacia mangium, Eucalyptus deglupta, Eucalyptus pellita, Gmelina arborea, Octomeles sumatrana, Khaya ivorensis, and Paraserianthes falcataria.

The manifestation of ITP came about in the 90’s. The official effort geared towards ITP only began in 1998. No sane governmental agencies would be willing to take this task. The long gestation period, huge investment required, coupled with numerous possibility for failure meant that only the “Big 6” had the resources and experience to tackle the assignment with  the greatest chance for success. The endeavour proves to be a daunting one; almost half of the allocated land within the licensed planted area was deemed unsuited for ITP. Gentle slope of 25 degrees and below is sought after for the most optimum growth of the fast growing exotic trees. The same rule applies for oil palm plantation. Encroachment by rural residence is an illuminating evidence of the State government’s failure to oversee the chain reactions that had rippled from the rampant natural resource exploitation of a mirage form of development.

Pest and diseases present imminent threats to the fast-growing exotic trees used in many of the State’s ITP.

helopelthis
Six-months old Acacia spp. affected by Helopeltis spp.

Helopeltis spp. are the most disruptive pest problem experienced in majority of the LPFs in the State. Symptoms include necrosis with devastating emphasis on the apical leaves, the phyllodes, frequent emergence of multi-leader stems, and crooked boles are among the more distinctive features of the pest problem.

Helopeltis spp. insects devour the apical leaves and shoots of the young Acacia treelets.
Helopeltis spp. insects devour the apical leaves and shoots of the young Acacia treelets.

Attack has greater probability to cause fatality on trees 6-months old and younger. Increased frequency of multi-stem incidence is synonym to loss of money, Multi-stem inhibits the expansion of the canopy. Visual indicator is well-documented at the three LPFs; 6-months old trees looking like 3-months old.

The direct mitigating action to reduce multi-stem incidences is by pruning. Pruning involves the removal of excessive branching; in this case, leader stems. The act of pruning inflicts mechanical damage on the trees as well as stress. This is basically ringing the dinner bell for the vectors (the insects) to start attacking the stressed trees. This correlation is the primary reason as to why available control method is being withheld.

Foaming indicating possible fermentation of the vascular bundle
Foaming indicating possible fermentation of the vascular bundle

Mechanically damaging the trees substantiate the increased susceptibility to Ceratocystis attack; Ceratocystis is a genus of fungi within the family Ceratocystidaceae. The symptoms include the foaming of the stem of young Acacia trees, usually before the stem becomes woody. The act of foaming indicates the attack to be on the vascular bundle within the stem; the “organ” responsible for transporting food and water in the plant.

Silviculture advocates on ITP in the State are looking at chemical control as well as preparing for the worst case scenario; of having to replace current species with the more resilient of fast-growing exotic species known in the region. At the moment, Eucalyptus spp., and Paraserianthes falcataria seem to depict positive consistency in the midst of the Helopeltis “epidemic”.

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