A survey project carried out by FFTC from 1991 to 1996, with the support of the Japanese government, showed that the production of tropical fruit in the region is badly affected by viral and bacterial diseases. Even the seedlings being planted in new orchards, and the mother stock which provide planting materials, are often infected.
In response to this situation, FFTC began in 1997 a three-year project on Virus-free Nursery Systems. It consists of five major activities:
As part of this project, a multidisciplinary team of plant pathologists, plant breeders and tissue culture experts was organized in 1998 to carry out a survey in Malaysia and the Philippines in February. The mission of the team was to assess some of the constraints facing a national disease-free nursery system for fruit trees, especially citrus and banana, as well as the benefits that might be expected from such a system.
Malaysia has not yet fully established a complete laboratory system for virus indexing of citrus. So far, most of the seedlings provided to growers are propagated from mother plants which appear to be healthy. There is the danger of latent infection in such a system, and in fact all orchards visited had trees which showed symptoms of greening or virus diseases. Samples were taken for laboratory testing, which showed that virus and greening were indeed present. This included newly planted orchards where the trees were less than five years old. Malaysia is eager to establish a virus-free nursery system for banana and citrus, and FFTC is planning to provide technical assistance in this program.
In spite of the disease problems, citrus production is giving Malaysian farmers a much higher income than rice or other crops. Farmers who shift to citrus from rubber or rice generally triple their incomes.
Citrus is not an export commodity in the Philippines, but is grown to meet the high domestic demand. Banana, in contrast, is a major export earner. The Philippines is the world's third largest exporter of banana, after Ecuador and Costa Rica. Banana for export are grown mainly on the island of Mindanao, which lies outside the typhoon zone. However, the majority of banana growers are smallholders producing banana for home consumption and the domestic market. Banana and plantain are grown all over the country in backyards, or as a mixed crop. Smallholders use relatively few commercial inputs, and get average yields of only 9.3 mt/ha, compared to average yields of 40 mt/ha on large plantations. For smallholders, banana are an insurance against hunger and an important source of cash income. Cooking bananas such as Saba are often used to supplement the more expensive grain staples, and are also processed into products such as banana chips.
Twenty years ago, Batangas province in Luzon, Philippines, was a major citrus producing area. However, the once thriving citrus industry has been almost wiped out by citrus greening and tristeza. Programs of orchard rehabilitation have been carried out, and new orchards established in other provinces, but the disease problem remains serious.
The survey team found that a high proportion of banana plants and citrus trees were infected with virus diseases. Banana were found to be infected with bract mosaic virus (BBMV), bunchy-top virus (BBTV) and cucumber mosaic virus (CMV). Common citrus diseases included citrus greening and citrus tristeza virus (CTV), besides citrus canker and various insect pests (rind borer and scale insects).
Bract mosaic virus is a new disease of banana in the Philippines, and is particularly common in Saba and other cooking bananas. The damage to Saba has been so great that many banana chip factories have been forced to shut down, because of the lack of raw materials. A rehabilitation program for Saba is now being carried out, in order to revitalize the banana processing industry.
The survey team suggested that to reduce disease incidence in banana, growers should treat banana as an annual rather than a perennial crop, and replant with disease-free seedlings every year. To rehabilitate citrus orchards, the Philippines plans to establish a national system for the production of disease-free seedlings.
Location: Malaysia, Philippines
Date: July-December 1998
Figure 1 Mass Production of Virus-Free Tissue Culture Banana Plants in Taiwan. These Are Sold at a Low Price to Thousands of Small-Scale Banana Producers
Figure 2 Banana Plantlets Grown by Tissue Culture, Ready for Distribution to Farmers
Figure 3 Banana Plantlets Produced by Tissue Culture Are Susceptible to Damage from Herbicides. a Mulch Gives Good Weed Control.
Figure 4 Mass Production of Virus-Free Citrus Seedlings As Foundation Stock, Vietnam.