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Today is :
Archives (2001)
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Controlling white rusts in chrysanthemums
by Junelyn S. de la Rosa
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October-December
2001
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Chrysanthemums in the highlands of Baguio, Benguet,
some parts of Tagaytay and Davao are sick with white rust
caused by the fungus Puccinia horiana Henn.
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| Pure cultures of (a) Paecilomyces
sp., (b) Verticillium sp. |
Chrysanthemum rust was first discovered in the
Philippines in 1961 by Teodoro et al., 66 years after it was
first reported in China and Japan in 1895. Today, white rust
has become more destructive than it was four decades ago.
Some chrysanthemum varieties that were resistant before are
now susceptible to the disease. Yield losses could be as high
as 80% especially when the plants are infected at a very young
age. A research team from Benguet State University (BSU) composed
of Dr. Luciana M. Villanueva (project leader), Ms. Teresita
Masangcay and Ms. Nordalyn Pedroche studied the alternate
hosts and disease cycle of P. Horiana and verified the effectiveness
of two fungal hyperparasites and bacteria for its control.
The study entitled: "Fungal hyperparasites and bacterial
antagonists as component of integrated disease management
program for chrysanthemum white rust" is a high impact
project funded by the Bureau of Agricultural Research of the
Department of Agriculture (DA-BAR).
The researchers found that the pathogen does
not infect other weed species in the area. Unlike other rust
fungi, white rust only stays in one plant or host for its
entire life. P. horiana produces two kinds of spores:
bicellular teliospores and unicellular basidiospores. Mature
teliospores germinate while still attached to the sori (a
compact mass of spores) while basidiospores are usually discharged
and spread by air, water, clothing, pruning tools, stakes,
pots, or strings.
Basidiospores are generally short-lived while
teliospores that grow on detached chrysanthemum leaves could
live up to two months. Both spores thrive in humid and moist
places and thus, white rust is a primary problem in the highlands.
P. horiana attacks the leaves of chrysanthemum
causing spotting and in severe cases, twisting and finally,
drooping of the leaves. Small, raised and discolored areas
called pustules appear on the lower surface of the leaves
and are beige to pink. These pustules produce the spores and
turn white when they mature. Under severe infection, the flowers
and stem can also be infected. Plants that are infected are
usually stunted and defoliated thus affecting the quality
of the cutflower yield.
The scientists recommend the use of two fungal
hyperparasites-- (Verticillium sp. and Paecilomyces
sp.) and bacteria (Pseudomonas sp. and Flavobacterium
sp.) in combination with compatible fungicides to effectively
control white rust. It has been observed that the pathogen
has already developed minor tolerance to some fungicides commonly
used to control the disease.
To effectively control the disease, they also
recommend that growers spray right after the plants recover
from transplanting. Spraying should be done every seven to
ten days with a fungicide and to make sure that the lower
leaf surfaces are thoroughly sprayed. This should be done
until the plants are about 30-38 cm tall. Spraying along the
aisles occasionally is also necessary to protect the late
developing side shoots.
Other practices that could help control the
disease are the following cultural management techniques:
1) Keeping the foliage dry at all times; 2) Removing infected
leaves from the plants and burning them immediately; 3) Avoid
watering plants late in the afternoon; 4) Using disease-free
planting materials; and 5) Removing old plants and burning
debris from the beds immediately as soon as the crop is cut
off. By integrating the hyperparasites and the bacteria with
fungicides and cultural management techniques, the scientists
are confident that the farmers and other ornamental growers
could stop white rust from being the much-dreaded nemesis
of chrysanthemums in the highlands. 
(Source: White rust: The nemesis of chrysanthemum
in the highlands by Dr. Luciana M. Villanueva of Benguet State
University, La Trinidad, Benguet; Tel No. 074-422-6504.) More Articles:
Vol. 3 No. 4 October-December 2001
»»
Outstanding technologies identified in nat'l R&D week
»» Thailand,
Philippines convene for agri cooperation
»»
Prospects for the ornamental industry in the new millennium
»» UPLB
scientists develop new hybrids of Philippine ornamentals
»» New management
techniques for exportable foliage plants
»» In
focus: a date with the "king of cut flowers"
»» Brighten
your homes with aglaonema
»» King
in red and green
»» Cashing
in with the 'lucky bamboo'
»» Turfgrasses:
the preferred ground cover
»» Catching
the invisible enemy with ELISA
»» Grow
dracaena godseffiana the easy way
»» Bromeliads:
the exotic plant
»» Wag that
fish-tail fern
»» Mass
propagating the 'doņas' through kulob system
»» Beauveria
mold bioinsecticide: safer control against orchid pests
»» Orchids
and mycorrhiza: a lesson from the wild
»» Controlling
white rust in chrysanthemums
»» Ways to
enhance palm seed germination
»» Prolonging
the vase life of cut flowers with ethylene adsorbent and Florafresh
»»
Mass producing the fragrant kamuning
»» The
national RDE program for ornamental crops
»» GMA
presents 2001 Gawad Saka awards
[More
2001 Articles]
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