Developing management strategies for Napier stunt disease

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A presentation prepared by Zeyaur R. Khan and Charles A.O. Midega for the ASARECA/ILRI Workshop on Mitigating the Impact of Napier Grass Smut and Stunt Diseases, Addis Ababa, June 2-3, 2010.

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Developing management strategies for Napier stunt disease

  1. 1. DEVELOPING MANAGEMENT STRATEGIES FOR NAPIER STUNT DISEASE Presented at the ASARECA/ILRI Workshop on Mitigating the Impact of Napier Grass Smut and Stunt Diseases, Addis Ababa, June 2-3, 2010 Zeyaur R. Khan and Charles A. O. Midega International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya
  2. 2. Napier Stunt Disease (NSD) is caused by a phytoplasma (16SrXI) and is transmitted by a leafhopper, Maiestas (Recilia) banda. The disease is spread by the leafhopper as well as through distribution of infected Napier cuttings. There may be other grasses in the field which are refugia for the leafhopper and phytoplasma and may contribute to the spread of the disease. For developing a robust management strategy, we need to fully understand the biology of the disease and its vector.
  3. 3. UNDERSTANDING THE DISEASE AND ITS VECTOR <ul><li>How is the epidemiology of the NSD? </li></ul><ul><li>Are there other vector(s) of the NSD? </li></ul><ul><li>What is the distribution of the vector(s)? </li></ul><ul><li>What percent of the vector(s) carry phytoplasma? </li></ul><ul><li>What are the contributions of vectors in spread of Napier stunt disease? How about the human factors? </li></ul><ul><li>What is the origin of the vector? How did it come to Napier grass? </li></ul><ul><li>Which other plants are infected now and which could be infected in future? </li></ul><ul><li>What is the distribution of these inoculum sources? </li></ul>
  4. 4. Can Resistant Varieties be Used in Managing Napier Stunt Disease? <ul><li>Are resistant varieties available? </li></ul><ul><li>Will farmers accept to grow the varieties? </li></ul><ul><li>Is resistance stable, durable? </li></ul><ul><li>What is the cause of resistance: resistance to vector or to phytoplasma? </li></ul><ul><li>What is the mechanism of resistance: antibiosis, non-preference/avoidance, tolerance? </li></ul><ul><li>Is resistance of high level or moderate level? </li></ul><ul><li>Are there biotypes of vectors/ phytoplasma which could break down resistance in future? </li></ul><ul><li>If the resistant variety has high level of resistance to vector, where will the vector move in future? </li></ul>
  5. 5. STUNT RESISTANT NAPIER?
  6. 6. If Resistant Varieties not Available or not Suitable? <ul><li>Are there other grasses which could replace Napier grass as fodder? </li></ul><ul><li>Will farmers accept those grasses to replace Napier? </li></ul><ul><li>Can the vector survive on those grasses? </li></ul><ul><li>Can the vector transmit phytoplasma on those grasses? </li></ul><ul><li>If those grasses are highly resistant to vector, where will the vector move in future? Food crops? </li></ul>
  7. 7. Bracharia sp. cv. Mulato
  8. 8. Cultural control <ul><li>Are there other grasses in farmers’ fields which could be refugia for vector and phytoplasma? </li></ul><ul><li>How can we identify those grasses? </li></ul><ul><li>Do the vectors move between Napier grass and refugia grasses? </li></ul><ul><li>What is the contribution of those grasses in spread of Napier stunt disease? </li></ul><ul><li>Is the same vector which transmits Napier phytoplasma also transmits phytoplasma on refugia grasses? </li></ul><ul><li>Can removal of those refugia grasses reduce phyoplasma infection on Napier grass? </li></ul>
  9. 9. Star grass infected with the same phytoplasma which infects Napier grass Obura et al. 2010. New Disease Reports
  10. 10. Could phytoplasma become a threat to cereal crops? <ul><li>Can the vector feed, survive and multiply on cereal crops-such as maize, rice, sorghum, millet, sugarcane, etc? </li></ul><ul><li>If yes, can the vector transmit phytoplasma from Napier to cereal crops? </li></ul><ul><li>If yes, can the phytoplasma affect productivity of cereal crops? </li></ul><ul><li>If vector-resistant varieties are used for phytoplasma control, can the vector move to cereal crops and can phytoplasma then become a threat to cereal production? </li></ul>
  11. 11. Sugarcane Rice Pearl Millet Finger Millet CAN PHYTOPLASMA AFFECT FOOD CROPS?
  12. 12. Electrophoresis of Phytoplasma DNA in food crops A M 1 2 3 4 5 M 1 2 3 4 5 M 1 2 3 4 5 M 1 2 3 4 5 Rice Finger Millet Sugarcane Pearl Millet PHYTOPLASMA CAN INFECT FOOD CROPS Contact author for results
  13. 13. <ul><li>WHAT IS THE MINIMUM NEEDED TO DEVELOP STRATEGIES FOR MANAGEMMENT OF NAPIER STUNT DISEASE? </li></ul>
  14. 14. FACILITIES TO MAINTAIN CULTURE OF INSECT VECTOR NEEDED
  15. 15. A REGULAR SUPPLY OF NSECT VECTOR NEEDED
  16. 16. MAINTAINING OF DISEASED NAPIER PLANTS WITH ACCESSION NUMBERS NEEDED
  17. 17. CONTAINMENT FACILITIES FOR MAINTAINING PHYTOPLASMA-FREE NAPIER GRASS VARIETIES AND GRASSES ARE NEEDED
  18. 18. ROBUST DISEASE SCREENING TECHNIQUES ARE NEEDED
  19. 19. PHYTOPLASMA FREE CULTURE OF VECTOR IS NEEDED TO DO BACK TRANSMISSION STUDIES
  20. 20. TRACKING THE MOVEMENT OF INSECT VECTOR ON REGULAR BASIS IS NEEDED
  21. 21. PCR AND LAMP FACILITIES TO DETECT PHYTOPLASMA IN PLANTS AND INSECTS ARE NEEDED
  22. 22. ICIPE’s PROPOSED MANAGEMENT STRATEGIES FOR NAPIER STUNT <ul><li>Work closely with National Programmes </li></ul><ul><li>Identify Napier Varieties with Moderate Level of Resistance to Insect Vector but with high level of durable and stable resistance to Phytoplasma. </li></ul><ul><li>Identify other fodder grasses not affected by phytoplasma </li></ul><ul><li>Survey farmers’ perception about resistant Napier varieties and fodder grasses selected </li></ul><ul><li>Survey and record natural hosts for insect vector and phytoplasma in farmers’ fields and study their effects on spread of Napier stunt disease for management </li></ul><ul><li>Avoid using high level of resistance to insect vector </li></ul>

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