Demonstration Citrus Orchard
In 1999, FFTC set up a citrus orchard demonstration project in Vietnam, with the cooperation of Vietnam's National Institute of Plant Protection.
Background
For the past twelve years, FFTC has been helping the region's citrus industry to deal with the problem of virus diseases and citrus greening. These diseases have devastated many citrus growing regions. Citrus growers find it difficult to keep their trees healthy, especially in tropical Asia. Even seedlings in plant nurseries are often infected with one or more of these diseases.
The Center's first step was a series of surveys carried out from 1988 to 1994, to find out how widespread the problem is in the region. (It was found to be very common).
The second step was to disseminate information about new molecular methods of diagnosing and indexing virus diseases, and providing national laboratories with training and the necessary enzymes. For the past five years, FFTC has also been helping national centers to set up plant nurseries for the production of virus-free seedlings.
The final step was to help farmers keep the seedlings healthy once they are planted out in the field. A field demonstration was set up in Vietnam to show farmers how to do this. Because virus and citrus greening diseases are spread by insect vectors, it may not be possible to keep the trees healthy indefinitely. However, if the region's citrus industry is to survive, trees must stay healthy long enough to give farmers a profit.
Demonstration Orchard in Vietnam
The aim was to demonstrate the possibility of protecting by integrated pest management a newly planted healthy orchard from reinfection with citrus greening, other key diseases and major pests. The orchard covers three hectares, and is 60 km northwest of Hanoi. The trees were transplanted in October 1999. They include Valencia orange, a traditional Vietnamese orange called Xadoai, and various kinds of mandarin.
Monitoring for Reinfection
ELISA and PCR tests for citrus greening and tristeza are conducted every three months. So far, neither disease has been detected in the demonstration orchard, even though 60% of the trees in nearby orchards were infected with greening. This implies that the countermeasures used in the demonstration orchard are effective.
Psyllids and aphids, the main vectors of greening and virus, are monitored once every two weeks, using traps in trap plants (Jasmine orange). They could not be monitored in the demonstration orchard, because control measures are keeping psyllid populations down to undetectable levels.
Control of Insect Vectors
In this part of Vietnam, psyllid populations increase sharply in March and April. Not only are there many psyllids at this time, but a high proportion of the psyllids carry greening disease. Therefore, good chemical control of psyllids must be carried out during this period. Trebon was sprayed every 7-10 days. Mites were controlled from late December to February with Mitox and mineral oil. Three sprays of Bordeaux mixture were used to control citrus canker in January/February.
The trees are now in flower, but will not be allowed to bear fruit for another year. Only a few fruit will be left on lower branches for flavor tests. In 2002, when the orchard bears its first crop, FFTC will be holding an international workshop. Participants will visit the orchard and discuss the methods used to keep it free of diseases and pests.
Index of Images
Figure 1 DR. Hong-Ji Su, Who Developed the Elisa and PCR Virus Indexing Tests Used in the Project
Figure 2 Inspecting Trees in FFTC Demonstration Orchard, Vietnam
Figure 3 Young Citrus Trees in FFTC Demonstration Orchard
