The following are some of the common Nursery and Plantation Diseases in Fiji and the Pacific. The table below shows some of the important tree species of Fiji. Common Name Fijian Name Scientific Name Sandalwood Yasi Santalum album Mahogany Mahogany Swietenia macrophylla Merbau Vesi Intsia bijuga Calophyllum Damanu Calophyllum vitiensis Kauri Pine Dakua Dakua makadre Caribbean Pine Pine Pinus caribbaea White Teak Yemane Gmelina arborea She-Oak / Ironwood Nokonoko Casuarina equisetifolia Diseases of nurseries: Damping-off of seedlings (Death of germinating and very young seedlings) Cure is not possible so nursery hygiene is recommended. Root rot, powdery mildew and foliar spots,foliage blight and shoot diebacks are also common nursery diseases caused by: Fusarium, Pythium, Phytophthora, Thanatephorus and Cylindrocladium. Plantation Diseases:
Root rot caused by fungi Armillaria, Phellinus and Rigidoporus. Most significant is Phellinus noxius. (Wide host range including breadfruit, cocoa and rubber). The fungus is endemic in the natural forest of most of the larger islands of Oceania (Ivory 1996) where it can infect living trees as a pathogen of roots and stems, or as a perthophyte (living on dead material of living hosts) of the heartwood, and as a sparophytic decay fungus on dead wood. Infection foci in plantations arise from remnant stumps of the native forest trees that have been felled. Further infections arise during plantation thinning activities and at clearfall. There are indications in Queensland that losses will be higher in second rotation forests and that biocontrol may be an effective control practice. Surveys in plantations of Salmwood in Vanuatu and of Mahogany (Swietenia macrophylla) in Fiji showed that P. noxius was present in most of the plantings in both countries. Ivory (1987) listed Pinus caribaea Morelet, P. merkusii and Araucaria spp. among the hosts of P. noxius but reported that mortality in pine plantations is usually negligible. A damaging disease in tropical forests of south-east Asia and the Pacific Islands is Pink Disease caused by Corticium salmonicolor. It causes mortality of the major branches accompanied by leaf cast due to invasion of the cambium and resultant girdling. Severe attack can spread to the whole crown but trees are rarely killed. Trees of any age may be attacked and the spread of the disease depends on the vigor of the host and on environmental conditions. Cylidrocladium blight caused by Calonectria quinqueseptata. This pathogen, along with other related fungi has proved to be one of the most significant disease problems facing the plantings of some species of Eucalyptus in Australasia and south-east Asia. Other wood-decay fungi associated with plantation losses in the south-western Pacific include Armillaria spp., A. mellea, P.Kumm. and A. tabescens and Rigidoporus vinctus. These are apparently only of minor importance compared with P. noxius. A fungus broadly identified as
Ganoderma lucidum associated with Agathis vitiensis and Pinus caribaea in Fiji was not pathogenic on P. caribaea. Ganoderma chalceum was reported on dicotyledonous trees from Fiji and Ganoderma austral. Ganoderma tornatum was reported from Grevillea robusta A.Cunn. In Tonga, and caused wood rot in Fiji and the Solomon Islands. A fungus identified as Clitocybe tabescens, this is now called Armillaria tabescens caused large scale mortality of Mahogany (Swietenia macrophylla) and Pinus elliottii Engelm. in Fiji. It is possible that the later reports of Armillaria spp. and A. mellea from Fiji refer to the same fungus. Insects and fungi: most insects and fungi are selective of the host species. In their natural environment, trees and shrubs normally attain a state of equilibrium with indigenous pests. However, when exotic trees and shrubs are planted, exotic pests can also be introduced. Quite often, these exotic pests readily adapt themselves to the conditions of their new habitat. In general, the risk of damage from pests is higher when the plants are physiologically weakened from planting on unsuitable sites, improper site preparation, inefficient planting, adverse climatic conditions, or neglect of weeding and other maintenance operations. But even healthy trees and shrubs are attacked at times. For many insects and fungi, no control measures are available; when this is the case, the best precaution is to plant tree and shrub species or varieties known to be resistant to the pests. The main precautions to be taken in guarding against possible future damage from insects and fungi are to plant tree or shrub species that are suitable to the climatic and soil conditions of the site, and to make surveys of indigenous pests to ensure that none are among the known forms to which the selected species is susceptible; but this is seldom easy, especially in view of the gaps in available knowledge on site requirements and susceptibility of exotic species to insects and fungi. To obtain this needed information, carefully controlled experiments should be initiated before developing large-scale planting programmes. Care taken in establishment and maintenance operations during the early years of a plantation (resulting in healthy vigorous young trees or shrubs) can help to make a plantation more resistant to insects and fungi. However, when evidence of pest attack appears, it should be investigated
promptly and the cause identified. Various control measures are available; these may be silvicultural, chemical, biological, or mechanical. Silvicultural measures include well timed, careful thinnings after establishment of the forest plantation. Through thinning, poor and suppressed stems are eliminated, maintaining the plantation in a thrifty and vigorous growing condition. In young plantations, prompt removal and destruction of infested trees and shrubs can be effective in preventing the spread of the pest attacks to the rest of the plantation. Where a threat of infection is known to exist, planting of tree or shrub mixed species also can be considered a silvicultural control measure. One disadvantage of mixed plantings is that subsequent forest management can be complicated; however, this may be avoided, at least partially, by planting alternate blocks or wide belts with different tree or shrub species, forming barriers to the spread of a pest or disease from the initial point of infection. Insects and fungi can often be checked by applications of appropriate chemical insecticides or fungicides. Usually, these chemicals are available as liquids (or wettable powder), dusts, or smokes. Spraying with hand-operated spray guns or portable mist-blowers is frequently used to control attacks in young plantations; with canopy closure, aerial spraying and dusting or smoking can be more effective and cheaper. Only previously tested and environmentally sound insecticides and fungicides should be prescribed for use. Biological control of insects has been employed with success in some situations; in most instances, the introduction of a parasite to control the insects is required. The greatest success in biological control is usually achieved after the problem has grown to epidemic proportions. Mechanical control, either by physically removing and destroying the pests or by eliminating the alternative hosts, can be effective.
There are number of strategies for controlling pest and disease outbreaks in forestry plantations, including integrated pest management and the use of registered pesticides and fungicides. Integrated pest management Even though integrated pest management (IPM) for forestry plantations is still in its infancy, It is recommended to use this method of managing pests due to its targeted use of chemicals and emphasis on long-term sustainability. Insecticides and fungicides As well as incorporating IPM principles for managing pest and disease outbreaks, there a number of registered insecticides and fungicides you can use on your timber plantation. We do not provide advice on how to control specific pests and diseases but we can refer to you organisations responsible for registering safe and effective chemicals. In plantation forests, the disease control benefits of fungicide application are shortlived and are not cost-effective Five successive years of aerial chlorothalonil application temporarily reduced disease symptoms but did not achieve complete disease control; infection levels rapidly returned to pre-treatment levels when application ceased Chlorothalonil (Bravo, Echo, Daconil) has been shown to effectively reduce infection levels in both plantation forests (ground and aerial application) and Christmas tree plantations, but fungicidal control is only economically viable in high-value Christmas tree plantations Sulfur-based fungicides are slightly less effective than chlorothalonil in controlling infection, but are less toxic and have less deleterious impacts on non-target organisms.