PhD

The study entitled "Management of water hyacinth using fungal
pathogens" was conducted in College of Agriculture, Vellayani,
Thiruvananthapuram during 1999-2002 period.
A survey was carried out for a period of one year at quarterly
intervals in four southern districts of Kerala to isolate fungi infecting
water hyacinth.
Myrothecium advena was the most commonly seen fungus followed
by Fusarium pallidoroseum irrespective of the season.
A positive correlation between the occurrence of fungi and
maximum temperature, relative humidity, total rainfall and number of
rainy days and negative correlation with maximum temperature was
observed.
Out of the 21 fungi tested for pathogenicity, 17 were found to be
pathogenic on water hyacinth. Only M. advena (61.11 %) and
F. pallidoros eum (53.44 per cent) caused more than 50% infection.
The Fusaria, Alternaria and Myrothecium isolated from water
hyacinth were identified as F. oxysporum, F. pallidoroseum,
F. moniliformae, A. eichhorniae and M advena, of which M. advena was a
new report on water hyacinth.
Host range of M. advena, F. pallidoroseum, F. equiseti and
C. gloeosporioides were studied. M. advena infected 27 cultivated and 45
weed plants, while F. pallidoroseum was limited to six cultivated and 20
weed plants.
Cell free metabolites of M. advena produced maximum damage of
97.75 per cent on water hyacinth followed by metabolites of F. pallidoroseum
(48.84 per cent). The cell free culture filtrate of M. advena could produce





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symptoms on eight cultivated and nine weed plants, while that of
F. pallidoroseum developed symptoms only on one weed plant
(Monochoria vagina/is). Toxicity of cell free metabolites was affected by
dilution, temperature and pH.
Based on paper chromatography, thin layer chromatography and
NMR spectral peak analysis the toxin produced by F. pallidoroseum was
identified as fusaric acid. Application of purified toxin on water hyacinth
plants produced typical symptoms resembling fungal infection.
Among the ten solid substtates tested F. pallidoroseum and
F. equiseti grew and sporluated well in rice bran and rice bran + coirpith.
Coconut oil cake and gingelly oil cake were the most favoured substrates
of C. gloeosporioides. Of the 14 liquid substrates listed maximum average
viable colonies of F. paflidoroseum, F. equiseti and C. gloeosporioides were
recorded in jaggery water, coconut water and coconut oil cake extract
respectively.
Under glasshouse condition simultaneous application of anilofos 24
% + 2,4-D 32 % EC (30 ppm) with F. paflidoroseum recorded 68.86 per
cent disease intensity while under trough condition, this combination gave
only 26.67 per cent disease intensity.
Dust formulation of F. pallidoroseum resulted in 20 per cent disease
while sequential application of 2.0 per cent CNSL and dust increased
disease intensity to 68.89 per cent. Spores in dust formulation remained
viable for one month at room temperature.
Wettable powder of F. pallidoroseum was formulated using
mycelium, talc, tween-80, glycerol and sucrose. This @ 5 g and 10 g/l 00
ml on 2.0 per cent CNSL sprayed plants recorded 82.22 and 97.78 per cent
disease intensity on water hyacinth plants. While under trough condition
application of wettable powder @ 5 g and 10 g/1 00 ml on 4.0 per cent
CNSL sprayed plants recorded 97.33 and 98.67 per cent disease.

Viability of spores in wettable powder formulation lasted for five
weeks under room temperature and for four months under refrigerated
condition.
Oil based formulation of F. pallidoroseum no" spores/ml) and
CNSL (2.0 per cent) recorded only 48.89 per cent disease intensity.
Field application using CNSL (5.0 per cent) and F. pallidoroseum as
WP formulation (@ 5 gll 00 ml) recorded a mean per cent damage of 91.43
on water hyacinth plants.
Safety test of formulated product and metabolites of F. pallidoroseum
revealed that they are safe on commonly seen aquatic flora and fauna.