Disease Management

FOREST DISEASE MANAGEMENT


INTRODUCTION

 

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.


SEED DISEASES AND CONTROL MEASURES

 

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.
Earlier reports show that seed mycoflora of neem during storage caused by Aspergillus spp. (Sinniah et al., 1983). Mehrotra and Pandey (1991) have recorded poor germination of neem seeds due to Fusarium species. Teak seeds are attacked by a number of fungi in storage and during weathering of fruits. Aspergillus flaus, A. niger, Chaetomium globosum, Curvularia pallescens, C. lunata, Fusarium moniliforme, F. oxysporum, Marasmius sp. and Stachybotrys atra. Singh et al. (1989) isolated Alternaria sp., Penicillium lanosum and Trichoderma viride from seedcoat and Fusarium sp. and Helminthosporium sp. from embryo of teak seeds. Pods of Dalbergia sissoo is attacked by Phoma sp. Other fungi recorded on pods include Glomerrella cingulata and Septothyrella dalbergiae (Pavgi and Singh, 1971). Fusarium spp. on seeds of Albizia lebbeck have been found to cause both pre-emergence and post-emergence damping-off disease together with Rhizoctonia solani, a soil inhabitant fungus.

CONTROL MEASURES :

  • Presence of contaminated or infected seeds in the seed lot may cause considerable spoilage of seeds particularly by molds if they are not properly stored. 
  • Timely collection, proper drying and storage of seeds under suitable temperature and humidity are necessary to protect the seeds from biodeterioration. 

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.


METHOD OF PREPARATION OF FUNGICIDE SOLUTION

 

Requirement:

  1. Fungicides
  2. Sprayer
  3. Bucket (5 litre, 10 litre, 25 litre)
  4. Water
  5. Soap liquid (Teepol etc.)


Method of preparation:
If any fungicide solution is to be prepared at the concentration of 1%, the following formula can be used:


                                                Dosage of fungicide
Weight of Fungicide (W) = --------------------------------------- x Volume of water
                                                Active ingredient of fungicide

(Wettable Powder percent)

For example:
            1% of Bavistin
W = -------------------------------- x 1000 ml of water
            50 (WP) of Bavistin
                                    W = 2 gm Bavistin can be mixed in 1 litre of water

DISEASE MANAGEMENT STRATEGIES
            The following measures should be followed for proper management of different disease problems in mist chamber, poly tunnels and nurseries.

  • Regular surveillance should be made in mist chambers, poly tunnels, shade house, nursery and clonal multiplication areas in order to check the incidence of different diseases at the initial stage.

  • Potting media should be properly sterilized (solar heating) before use.

  • Cleanliness and hygiene are very important inside the mist chambers, poly tunnels and shade house. Infected tissues should not be taken inside these structures.  The nursery and its surroundings should be kept neat and clean.

  • Proper drainage system should be provided in the nursery. Avoid excessive moisture and shade in clonal complex structures.

  • Avoid injury to the seedling roots or stem or any part of the plants.

  • Mechanical removal of affected portions of the plant and burnt them outside the clonal complex area.

  • Severely affected plants should be kept in isolation. The fully affected and dead plants should be burnt them outside the clonal complex area in order to prevent the inoculum build up and disease spread.

  • Application of biofertilizers such as Vesicular Arbuscular Mycorrhizae (VAM fungi), Ectomycorrhizal fungi, Rhizobium, Azospirillum, Phosphobacterium etc and bio-control agents such as Trichoderma viride, T. harzianum, Pseudomonas fluorescence etc can be done during raising of seedlings.  When added to the soil, these biofertilizers act as a bio-control agents and decrease or inhibit the growth of various soil-borne pathogens.  Hence, suitable biofertilizers should be applied in nursery stage for production of quality planting stock and their better survival and establishment in field conditions.

  • Use of quality seeds and disease resistant planting materials. Disease problems in Clonal Multiplication Areas (CMAs) can be controlled to a greater extent by ensuring the genetic diversity of the crop, by increasing the number of clones and manipulating their spatial distribution in planting area. Because the genetic uniformity of the plants render them high incidence of fungal pathogens and high spread to all the plants in CMAs.


CONCLUSION

 

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.


© All Rights Reserved. TNAU-2014.