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The battle against chrysanthemum white rust by Rita T. de la Cruz

April-June 2004 Volume 6 No. 2

With its high demand in the global market, chrysanthemum (Dendranthema grandiflora) is considered a high value cash crop in the Philippines. From 1985 to 1993, chrysanthemum growers enjoyed a tremendous increase in production resulting to a stable growth of cutflower exports. Japan was the Philippines' largest importer of chrysanthemums accounting for the 97% of its total export of cutflowers.

Although there was a great increase in export for quite sometime, chrysanthemums are unable to penetrate the global market due to the inability of local growers to meet the quality and quantity standards. One well-known nemesis of chrysanthemum growers is white rust, a major disease in chrysanthemum that could seriously affect its overall production.

War against white rust
Chrysanthemum white rust was first discovered in the Philippines in 1961, seven decades after it was first reported in China and Japan in 1895. White rust is caused by Puccinia horiana Henn, a filamentous fungus that grows and reproduces on host plants. The disease first appears as yellow spots on the upper surface of the leaves, which would later become sunken and necrotic. Prominent pustules develop subsequently on the lower surface of the leaves. They appear beige colored at first and then the pustules mature to a waxy white. The disease affects mainly the leaves but it could also spread to stems, bracts, or even the flowers. Severely infected leaves dry up and hang along the stem. When the white rust attacks during the early stage, the damage could result up to 80% yield loss.

Helpful microorganisms fight back
A major concern of chrysanthemum growers is how to effectively manage white rust with cheap and environment-friendly technology.

A research team from the Department of Plant Pathology of the Benguet State University (BSU) composed of Dr Luciana M. Villanueva (project leader), Ms Teresita Masangcay and Ms Nordalyn Pedroche developed an efficient biocontrol technology for commercial chrysanthemum production using helpful microorganisms: a fungal hyperparasite and two bacterial antagonists. They compared their efficacy with the farmer's existing practice in managing the white rust, a calendar-based spraying of fungicides.

The researchers used a fungal hyperparasite (Verticillium sp.) and two bacteria antagonists (Pseudomonas sp. and Flavobacterium sp.) As biocontrol agents. They also identified some indigenous materials that carry these microbial antagonists, namely: arrowroot, canna, cassava, galiang, potato, sweet potato, taro, yam, and bentonite. According to the result of their study, Verticillium sp. was higher in potato, followed by bentonite and canna while Pseudomonas sp. and Flavobacterium sp grew better in arrowroot and canna, respectively.

To test the efficacy of the newly developed biocontrol technology, the study was conducted under greenhouse condition vis-à-vis the existing farmer's practice and the untreated plants.

The researchers found that the combined application of the three microorganisms resulted to a significantly lower disease incidence compared to the calendar-based fungicide spraying, which is the existing management practice of chrysanthemum growers against white rust.

Moreover, chrysanthemums sprayed with the microbial antagonists gave significantly lower disease severity rating than the unsprayed plants although, the scientists admit that the result was still at par with the farmers' practice.

On the financial benefit, the researchers found that the use of microorganisms gave a slightly higher return of investment, at 56.41%, over the farmers' practice with 53.32%. Moreover, the reduction of fungicide expenses enables farmers to save up to P59,000 per hectare.

The study entitled: “Indigenous Microorganisms for Cost-Effective Management of Chrysanthemum White Rust” is a high impact project funded by the Bureau of Agricultural Research, Department of Agriculture.

For more information: Dr. Luciana M. Villanueva of the Horticulture Research and Training Institute, Department of Plant Pathology, BSU, La Trinidad, Benguet at tel. no. (074) 422-6504 or e-mail at lucy@bgo.csi.com.ph

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