Submitted to: Subtropical Plant Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1997
Publication Date: N/A
Interpretive Summary: When searching for effective natural enemies to use against an insect pest, an effective strategy is to conduct the search where the pest originated. The country of origin is likely to contain parasites or predators that have, through time, become effective against the pest. In the case of the sweetpotato whitefly, some scientists believe the pest originated from the Orient. Another reason for searching in Asia is because the climate is similar to that of south Texas, one area the natural enemies are intended for use. This improves the chances that the imported insects will be adapted to the area where they are released. Therefore, we set out to search for natural enemies of the sweetpotato whitefly in 5 countries in Southeast Asia: Taiwan, the Philippines, Malaysia, Indonesia and Thailand. Four trips were performed over a period from November 1993 to October 1995. The collections resulted in the discovery of 28 potential control agents of fthe whitefly: 25 were insect parasites or predators, and 3 were disease agents. Two of the parasitic insects are probably new to science. Many of the parasites are currently being tested for their ability to control the whitefly in laboratory and field tests in Texas, California and Arizona.
There is speculation that the sweetpotato whitefly Bemisia tabaci (Gennadius) (Biotype 'B') may have originated in the Orient because of the diversity of endemic Bemisia species, and effective natural enemies are likely to be found in the region. Parasitoids native to Southeast Asia also may be adapted to intended areas of introduction in south Texas, because of climatic similarities. Accordingly, 4 separate explorations fo natural enemies of B. tabaci were conducted in the Philippines, Taiwan, Malaysia, Thailand and Indonesia over a period from November 1993 to October 1995. The collections resulted in the importation into the U.S. of 2 geographic strains of the aphelinids Encarsia and Eretmocerus, 2 coccinellids, an unidentified syrphid, and 3 entomopathogens. One strain of Eretmocerus from Taiwan may represent an undescribed species; another strain of Eretmocerus from Thailand currently is being described as a new species. No natural enemy cultures were obtained from Malaysia. Many of the species of Encarsia and Eretmocerus have shown potential for suppressing populations of the whitefly during evaluations conducted in south Texas and other parts of the U.S. The aphelinids collected were classified according to DNA banding patterns using RAPD-PCR techniques. The classificaton revealed an interesting diversity of patterns in both genera in Taiwan relative to the other countries. It is interesting to speculate whether the diversity of genetic patterns discovered is simply a reflection of collection effort, or an indication of underlying evolutionary diversity.