FOREST DISEASE MANAGEMENT
Forests provide multipurpose benefits such as timber, fodder, fuel and minor forest produces. They also help in conserving soil and water, offering food and shelter for wild life, adding to the aesthetic value and recreational needs of man. Forestry has the prime objective of developing and protecting forests for their maximum productivity. Diseases and insect pests constitute major biological determinants of forest productivity, particularly in nurseries and plantations. They cause heavy damage to seedlings and hence reduce both quantity and quality of planting stock. Large-scale mortality in the nursery due to disease and pest problems could seriously affect the plantation programme by reducing the stock of seedlings. In plantations, they cause major problems resulting in the reduction of biomass production or loss of valuable germplasm collections. Further, the infected seedlings are weakened and unable to withstand the adverse field/plantation conditions. Thus, the economic loss resulting from nursery diseases and insect-pests are considerable. Therefore, raising disease free, healthy tree seedlings is not only important for maintaining a good nursery stock but also essential in establishing a healthy stand in the field for better productivity. This paper reviews and highlights different disease problems like damping-off, leaf spot, leaf blight, leaf rust, powdery mildew, stem rot, seedling wilt, root-rot and collar-rot caused by various pathogens on economically important fast growing tree species such as Albizia lebbeck, Ailanthus excelsa, Azadirachta indica, Dalbergia sissoo, Gmelina arobrea, Pongamia pinnata, Tectona grandis and Terminalia chebula in nursery and plantations. The influence of different factors on the occurrence, proliferation and spread of the diseases were analysed. Effective management of these disease problems by integrating control methods like cultural practices, sanitation, fungicide application, use of bio-control agents and biofertilizers were also discussed in detail in the present study.
Seeds are prone to attack by the fungi while still on the tree, during post harvest operations in the field, storage and subsequent handling prior to sowing. The fungi may be borne as surface contaminants or they may be present in the seed coat or may penetrate the seeds even deeper attacking the embryo and thus damage the seeds to varying extents. It has been recorded that seeds of some leguminous (pod bearing) tree species are quite susceptible to attack by fungi while they are inside the pods on the trees and they are also damaged considerably in case they are not timely collected and properly stored. Number of fungi belonging to Mucorales and Fungi Imperfecti such as Alternaria, Aspergillus, Cladosporium, Colletotrichum, Curvularia, Fusarium, Gloeosporium, Lasiodiplodia, Mucor, Penicillium, Phoma, Phomopsis etc are associated with seeds of various forestry species of which species of Fusarium, Lasiodiplodia, Gloeosporium and Phoma cause deep seated infection and damage the embryo.
The seeds after collection should be dried so that the seed moisture content is reduced to about 10% on oven dry weight basis. Besides, it is advisable to do seed dressing with a suitable fungicide (Ceresan) @ 4-5 gm/ kg of seeds. This prophylactic treatment is easy and economical and serves the dual purpose: firstly it helps in preventing fungal deterioration of seeds in storage and secondly it minimizes the chances of seed borne pathogenic fungi attacking the seedlings in the nursery.
DISEASE MANAGEMENT STRATEGIES
Selected genetically superior seeds as well as disease resistant planting materials are essential for successful forestry programme in order to withstand and overcome adverse environmental factors and emerging disease problems. Hence, genetic improvement of clones is undertaken continuously creating more and more population of genetic variability for further selection of improved genotypes against the diseases for better production of plantation forestry.
REFERENCE: PATHOLOGICAL PROBLEMS OF ECONOMICALLY IMPORTANT FOREST TREE SPECIES IN INDIA – AN OVERVIEW, V. MOHAN, Division of Forest Protection, Institute of Forest Genetics and Tree Breeding, coimbatore.
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