To: "Jarungsit Limsila"
Date: Tuesday, 17 February, 2009, 11:32 AM
Dear friends and colleagues:
You may be aware that two insects have been causing serious damage to cassava in Thailand during this past year. One is the spiraling white fly (Aleurodicus disperses), which has long existed in many countries in Asia, on many different crops, but seldom did serious damage to cassava. Last year the infestation was quite severe. Even so, this insect affects mostly the lower leaves and thus has less impact on yield. Spraying insecticides may be counterproductive as it may kill the biological control agents.
The second insect is more worrisome. In many parts of Asia we have had a minor problem in cassava with the striped-mealy bug, Ferrisia virgata, which caused only minor damage. However, late last year and especially during the current dry season in Thailand, there is a serious mealy bug infestation in various parts of the country. Dr. Bellotti, the CIAT cassava entomologist, who visited Thailand in October, suspected that the increased damage was done by one or more new species of mealy bugs, possibly Phenococcus manihoti and/or Phenococcus herrinni, which have also caused serious damage in Africa and Latin America, but have not previously been observed in Asia (including India). Thai entomologists agree that this is probably a new and more dangerous species, and they are trying to identify the exact species and possible biological control agents. Since CIAT/IITA collaboration during the 1980s was very successful in bringing a similar new infestation of P. herrinni in Africa under control, we may consider a similar effort in Asia with the possible introduction of effective biological control agents from Latin America into Asia. But before this is done, we first need to identify the exact species causing the damage and to get some indication of the seriousness of the problem and the extent of its spread. Thus, with this Email, I would like to request everyone to report to the CIAT-Bangkok office any serious or unusual infestations of both the whitefly and mealy bugs (or other insect or disease problems) on cassava in your area.
In addition, since mealy bugs are easily transported on planting material, it is very dangerous to take any stakes or vegetative planting material across borders, especially from Thailand, but even more so from Africa, Latin America or India (where cassava mosaic disease is a serious problem). Since these new insect pests have the potential to devastate the cassava industry in all of Asia, your help and collaboration is essential to bring this problem under control.
With best regards, Reinhardt
Reinhardt Howeler
CIAT, c/o FCRI, Dept. of Agriculture
Chatuchak, Bangkok 10900, Thailand
Office telephone: +66-02579-7551
Office telephone and fax: +66-02940-5541
Mobile phone: +66-089-2005799
Home phone: +66-02960-3839
Email: r.howeler@cgiar.org
ciat-bangkok@cgiar.org
For Vietnam C/c: Dr. Hoang Kim
Faculty of Agronomy, Nong Lam University
Linh Trung Ward, Thu Duc District,
Ho Chi Minh City, VIETNAM
Email: hoangkim_vietnam@yahoo.com
hoangkim@hcmuaf.edu.vn
Mob. + 84. 903 613024
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