Integrated plant disease management
By M. Mithal Jiskani
Feb 26 - Mar 04, 2001
The word integrated means combination, implemented as bringing together of individual control measures into a collective operation. The disease management means to check, prevent or control diseases by a judicious use of various methods of control, with the intention of reducing the incidence (damage or harm), caused by diseases to an economically acceptable level. In other words, integrated plant disease management is a programme, in which nature, the farmer (grower) and pesticides (fungicides or so) together combine to control plant disease. It means application of all those resources and practices, which may help, initially for prevention and finally to control plant diseases, is called Integrated Plant Disease Management.
There are so many methods, which are applicable, either adopting singly or in combination one with another, but the use of several techniques in combination, usually is more successful and most efficient, than any one method used alone.
Integrated disease management can lead to less expensive agricultural production technology, a substantial reduction in pesticides use, a greater stability in vegetation system, and an improved environment. It is because that integrated plant disease management is a mix of biological, cultural and chemical practices, with the involvement of all preventive and curative control measures against diseases.
However, several methods of plant disease management are being practiced. Kamal and Moghal (1968) suggested;
(1) Prophylactic measures
(2) Chemical control and
(3) Cultivation of disease resistant varieties. Prophylactic measures include
(a) Exclusion: consists quarantine, imposing embargo, inspection and certification of the planting stock;
(b) Eradication of source of infection: It includes eradication of alternate hosts, overwintering hosts, weeds, diseased plants or plant parts, and
(c) Sanitation: refers to destruction of plant debris or plant residues lying in the soil, use of healthy seed obtained from healthy crop or must be treated by suitable method, roguing or removal of diseased plants from a crop, pruning, disinfection of nursery beds, crop rotation, tillage operations, time of sowing, irrigation and drainage. Chemical control may be considered under
(a) seed treatments such as
(i) dry seed treatment and
(ii) dip method,
(b) Spraying and dusting (as soon as disease appears in the crop).
According to Walker (1968), control measures may be divided into two major groups: prophylaxis and immunization. Prophylaxis may be considered under three sub-groups
(b) eradication and
(c) direct protection. Exclusion includes compulsory quarantine and inspection, embargo, voluntary inspection and certification of planting stock and perishable fruits and vegetables at shipping points. Eradication consists eradication of alternate hosts; eradication of wild or other overwintering hosts; eradication of overwintering debris as source of primary inoculum by rotation; sterilization; and/or sanitation; eradication of pathogen from propagative parts of the host such as seeds, tubers, and bulbs; eradication from growing parts of the host by fungicides, after infection has occurred. Direct protection refers to spraying and dusting of foliage. Some seed treatments are eradicant, others are protective. Some of the other direct protective measures in common use are regulation of environment, timing of planting, cultivating and harvesting to favour the host and discourage the pathogen, harvesting and handling practices, pre-cooling, pre-storage curing, protection from frost, sub-oxidation, heat and ray injuries, correction of mineral deficiencies. Immunization refers to improvement of resistance of the host to infection and to disease development, commonly referred as disease resistance.
Wheeler (1969) recommended:
(a) Plant disease legislation
(b) Inspection of plant produce
(c) Elimination of pathogens from planting material.
(a) Direct removal of pathogen
(b) Elimination by cultural practices
(c) Destruction of pathogens.
3. Protection through chemicals: and
4. Cultivation of resistant varieties.
According to Agrios (1970) various control methods could generally classified as below:
1. Regulatory methods: (Quarantine and inspection).
2. Cultural methods: (Host eradication, Crop rotation, Sanitation, Improvement of growing conditions of plants, Creating conditions unfavourable to the pathogen and Tissue culture).
3. Biological methods: (The Breeding and use of resistant varieties, Cross protection and Interference, Hyperparasitism, Control through Trap crops and Antagonistic plants).
4. Physical methods (Control by heat treatment, Disease control by refrigeration, Radiation and Chemical Control).
5. Methods of plant disease control with chemicals: (Foliage sprays and dusts, seed and soil treatments, treatment of tree wounds, control of postharvest diseases, disinfestation of warehouses, control of insect vectors).
Nyvall (1979) proposed that following controls either alone or in combination disrupt the combination of factors necessary for disease development.
1. Sow resistant varieties
2. Practise crop rotation
3. Plow under infected residue
4. Sow disease free seed
5. Practise sanitation
6. Do not sow potential hosts adjacent to collateral host plants.
7. Practise good weed control
8. Rogue infected plants
9. Apply foliar fungicides
10. Apply a fungicide seed treatment
11. Ridge soil around base of plant
12. Do not cultivate when foliage is wet
13. Follow a good soil fertility programme
14. Avoid cultivation after wilt symptoms
15. Sow cultivars whose maturity may allow for escape from certain diseases.
16. Vary the sowing date to escape disease
17. Flood fallow
According to Hafiz (1988), there are four principles of plant disease control:
(1) Exclusion of the cause i.e.
(a) exclusion of unfavourable conditions causing nonpathogenic disorders and
(b) exclusion of plant pathogens in case of infections diseases;
(2) Rectification of unfavourable conditions in case of non-pathogenic disorders and eradication of pathogens;
(3) Protection of susceptible plants, and
(4) Use of resistant varieties.
Pandey (1992) discussed Prophylaxis and Immunization or disease resistance, with explaining that the prophylaxis include
(a) Exclusion of the parasite
(ii) Inspection of Certification; and
(b) Eradication of the parasite
(i) Crop rotation
(ii) Removal of infected parts
(iii) Elimination of alternate hosts
(iv) Destruction of wild hosts and weeds
(vi) Improved cultural practices i.e. raising of beds, change in planting season, obtaining seed from disease free locations, proper manuring, mixed cropping, soil hygiene, amendment of soil conditions, soil sterilization and partial sterilization, biological control; and
(c) Direct protection (through chemicals).
Lucas et. al. (1997) outlined three major types of plant disease management
(1) Genetic resistance (resistant cultivars),
(2) Prevention and
(3) chemotherapy (systemic chemicals). Among these, prevention includes
(a) Avoidance of pathogens by
(i) site selection and
(ii) Planting date,
(b) Protection of plants by means of
(i) environmental manipulation and
(c) Eradication of pathogens by adopting
(i) Cultural practices viz. crop rotation and sanitation,
(ii) removal of alternate hosts,
(iii) biological control,
(iv) chemicals and
(v) heat treatment,
(d) Legislation including
(i) Quarantine and
(ii) regulatory measures.
It is clear from the above outlined features that disease management practices are interrelated, therefore it is very difficult to simplify the integrated disease management methods. Hence, the growers (farmers), as well as agricultural extension and research workers must know a whole crop production technology alongwith nature and causes of the diseases, after that most easy, less expensive, improved and profitable integrated plant disease management methods can be decided and implemented, according to a particular disease of a particular crop.
1. Agrios, G.N. 1970. Plant Pathology. 2nd Print., Academic Press, New York. pp: 629
2. Hafiz, A. 1988. Plant Disease Control-Preventive Measures. In "Field Crop Diseases (Plant Disease Diagnosis Manual Vol.2), Edited by: Ahmed, I and M. Aslam. CDRI, NARC, PARC, Isldmabad: pp: 112-120.
3. Kamal, M. and S.M. Moghal. 1968. Studies on Plant Diseases of South West Pakistan. ARI, Tandojam pp: 207.
4. Lucas, G.B., C.L. Campbell and L T. Lucas. 1997. Introduction to Plant Diseases: Identification and Management. 2nd Ed. pp: 364.
5. Nyvall, R.F. 1979 Field Crop Diseases Handbook. pp: 436
6. Pandey, B.P. 1992. A text book of Plant Pathology: Pathogen and Plant Disease. Reprint of 2nd Ed. pp: 532.
7. Walker, J.C. 1968. Plant Pathology. 3rd Ed. McGRAW-HILL Book Co., N. York. pp: 819.
8. Wheeler, B.E.J 1969 An Introduction to Plant Diseases.
Reprinted by National Book Foundation, Pakistan. pp: 374
The author is Assistant Professor (Plant Pathology), Sindh Agriculture University, Tandojam.