Integrated Disease Management

Integrated Disease Management

Integrated plant disease management (IDM) can be defined as a decision-based process involving coordinated use of multiple tactics for optimizing the control of pathogen in an ecologically and economically. In most cases IDM consists of scouting with timely application of combination of strategies and tactics. These may include site selection and preparation, utilizing resistant cultivars, altering planting practices, modifying the environment by drainage, irrigation, pruning, thinning, shading, and applying pesticides, wherever required. But in addition to these traditional measures, monitoring environmental factors (temperature, moisture, soil pH, nutrients, etc.), disease forecasting, and establishing economic thresholds are important to the management scheme (Khoury and Makkouk, 2010).

These measures should be applied in a coordinated integrated and harmonized manner to maximize the benefits of each component. For example, balancing fertilizer applications with irrigation practices help to promote healthy and vigorous plants. However, this is not always easy to accomplish, and “disease management” may be reduced to single measures exactly the same as the ones previously called “disease control.” Whatever be the measures, they must be compatible with the cultural practices, essential for the crop being managed.

The basic objectives of any IDM program should be to achieve at least the following:

  • reduce the possibility of introducing diseases into the crop
  • avoid creating conditions suitable for disease establishment and spread
  • Simultaneous management of multiple pathogens
  • Regular monitoring of pathogen effects, and their natural enemies and antagonists as well
  • Use of economic or treatment thresholds when applying chemicals
  • Integrated use of multiple, suppressive tactics.

Components of Integrated Disease Management

The major components of disease management include host-plant resistance, cultural practices, biological control and chemical control. Even though these components will be dealt individually, it should be mentioned that often the different components are complementary to each other with strong interaction among and between them and the environment. It is essential to break away from relying on a single-technology and to adopt a more ecological approach for betterl understanding of the population biology at the local farm level and to rely on the integration of control components which are readily available to the resource-poor farmers (Thomas, 1999).

Acceptable pest level:

IDM holds that eradication or wiping out the entire population is impossible. Therefore, the emphasis should be for keeping the pathogen population at an acceptable level that is achievable, economically affordable and environmentally safe.

Monitoring:

Regular crop monitoring and record keeping provides reliable information to guide an IDM program. To monitor effectively for disease incidence and development, it is important to inspect foliage and flowers preferably, at weekly interval. Detecting diseases early makes the control easier, with only a spot spray or other localized action.

Host-plant resistance:

Host plant resistance is an important tool to control diseases of major food crops in developing countries, especially wheat, rice, potato, cassava, chickpea, peanuts and cowpea. The use of resistant varieties is very much welcomed by resource poor farmers because it does not require additional cost and it is environment-friendly. Rice varieties resistant to rice blast, bacterial blight, rice tungro and brown spot are widely used. The resistance is often durable, thanks to proper management of genetic diversity by employing gene rotation, multilines and cultivar mixtures, a strategy that proved effective in reducing disease damage in natural ecosystems. Such success stimulated interest in extending the principles of genetic diversity for disease control to other crops in developing countries (Leung et al., 2Late blight is considered as one of the most important biotic constraints for potato production in many developing countries including many from Latin America, which are considered as the center of origin for potato crop. Traditionally this disease is controlled by several fungicide spays, but the emergence of fungicide resistance in many locations and the increasing cost of their application, encouraged the search for other control strategies. Rusts have been known to cause serious disease on wheat since its domestication. The use of genetic resistance is still the most economic and feasible mode of disease control. Genetic resistance is often based on a limited number of major genes that are readily overcome by evolving pathogen races. With the reduction of genetic diversity in the wheat cultivars planted over large areas globally, serious rust epidemics are being recorded whenever new aggressive virulent rust races emerge. A typical example is the yellow rust epidemics that spread from East Africa to Central and South Asia and North Africa during the 1980’s and 1990’s. Presently the breakdown of Yr27, a gene used to replace Yr9, and the emerging stem rust race Ug99 are threatening 80-90% of commercial wheat varieties grown worldwide (Hodson and Nazari, 2010).

Late leaf spot caused by Phaeoisariopsis personata and rust caused by Puccinia arachidis are two most destructive foliar diseases of peanut worldwide. Host plant resistance has been used recently as one control component and a number of peanut cultivars such as ICGV 89104 and ICGV 91114 are now available. Field trials conducted in India showed that these cultivars yield 55-60% more than the local cultivars, and the severity of both the diseases is significantly lower in these than in the local cultivar Similarly, peanut varieties resistant to peanut rosette virus disease which causes serious losses in Africa have been developed (Reddy, 1998).

Cultural practices:

For many decades’ fungicides played an important role in disease control. In the 1960s, systemic fungicides started gradually to replace the older non-systemic chemicals with more effectiveness and specificity in disease control. Very quickly, triazole fungicides gained 24% of the total fungicides market (Hewitt, 1998). However, the non-systemic fungicides such as mancozeb and chlorothalonil plus copper and sulpher-based products continued to have a good share of the market, especially in developing countries because of their lower cost. More recently, new classes of fungicides were developed with significant impact on disease control. These include anilinopyrimidines, phenoxyquinolines, oxazolidinediones, spiroketalamines, phenylpyrroles, strobilurins and activators of systemic acquired resistance. However, the development of pathogen populations showing reduced sensitivity to many of the newly developed products posed a serious challenge that the traditional fungicides (e.g. sulpher, folpet, etc.) did not face. The availability of a variety of new products, with narrow and broad specificity, offer important disease control options, however, their practical application continues to face the risk of selection of resistant pathogen populations (Gullino et al., 2000). Experience accumulated over the last few decades clearly showed that fungicidal application had a better impact when used within an IDM strategy In addition, public concern has increasingly influenced the fungicide industry in developing effective products with low mammalian toxicity and environmental impact and low residues in food, to meet international health standards and compatibility in integrated pest management programs .

Biological control:

Success in using microorganisms against plant pathogens started with the control of crown gall with Agrobacterium radiobacter K84 (Kerr, 1980), and that of seedling blights caused by Pythium and Rhizoctonia with Trichoderma harizanum, Gliocaladium virens and Streptomyces griseus (Cook et al., 1996). However, the use of naturally occurring bio-control agents (antagonists) of plant pathogens can be traced back to many centuries through the traditional practice of crop rotations that primarily permit the reduction of pathogens’ inoculum potential in the soil below injury level. This approach is still the most important single component, in both developed and developing countries used to manage root pathogens. This process is often accelerated by adding composts or manures, which enrich the soil with antagonistic micro flora.

Advantages:

Integrated approach integrates preventive and corrective measures to keep pathogen from causing significant problems, with minimum risk or hazard to human and desirable components of their environment. Some of the benefits of an integrated approach are as follows:

  • Promotes sound structures and healthy plants
  • Promotes sustainable bio-based disease management alternatives
  • Reduces the environmental risk associated with management by encouraging the adoption of more ecologically benign control tactics
  • Reduces the potential for air and ground water contamination
  • Protects the non-target species through reduced impact of plant disease management activities.
  • Reduces the need for pesticides and fungicides by using several management methods
  • Reduces or eliminates issues related to pesticide residue
  • Reduces or eliminates re-entry interval restrictions
  • Decreases workers, tenants and public exposure to chemicals
  • Alleviates concern of the public about pest & pesticide related practices
  • Maintains or increases the cost-effectiveness of disease management programs

Conclusion:

Integrated disease management (IDM) is a disease control approach that uses all available management strategies to maintain disease pressures below an economic injury threshold. It does not advocate a routine chemical application program to prevent disease, but promotes the integration of cultural, physical, biological and chemical control strategies. The routine application of fungicides for insurance purposes is not appropriate, as it does not focus the proper attention on the real problem and can lead to resistance and potential environmental issues. Added benefits of IDM are that disease control is greater than that achieved by individual method.

References:

  • Gullino ML, Leroux P and Smith CM. 2000. Uses and challenges of novel compounds for plant disease control. Crop Protection 19: 1-11. Hewitt HG. 1998. Fungicides in Crop Protection. CAB International, Wallingford, UK.
  • Hodson, D. and Nazari K. 2010. Serious outbreaks of wheat stripe or yellow rust in central and west Asia and north Africa – March/April 2010. Borlaug Global Rust Initiative, Newsroom, Rust in the news, April 2010 News Items. http://globalrust.org/traction/ permalink/Pathogen206 Kerr A. 1980. Biological control of crown gall through production of agrocin 84. Plant Disease 64: 25-30.
  • Khoury W. El and Makkouk K. 2010. Integrated plant disease management in developing countries. Journal of Plant Pathology (2010), 92 (4, Supplement), S4.35-S4.42 Edizioni ETS Pisa, 2010 Knight SC, Anthony VM, Brady AM, Greenland AJ, Heaney SP, Murray DC, Powell KA, Schultz MA, Spinks CA.
  • Leung H, Zhu Y, Revilla-Molina I, Fan JX, Chen H, Pangga ., Vera Cruz CM and Mew TW. 2003. Using genetic diversity to achieve sustainable rice disease management. Plant Disease 87: 1156-1169.
  • Reddy DVR. 1998. Control measures for the economically important peanut viruses. In: Hadidi A., Khetarpal R.K., Koganezawa H. (eds). Plant Virus Disease Control, pp. 541-546. APS Press, St, Paul, MN, USA.
  • Thomas MB. 1999. Ecological approaches and the development of “truly integrated” pest management. Proceedings of the National Academy of Science USA 96: 5944-5951.


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