Abstract:
Fungal diseases, basal rot (Fusarium oxysporum f. sp. cepae) and leaf twister
(Colletotrichum gloeosporioides) are the main problem in red onion
cultivation in Jaffna, Sri Lanka. Disease symptoms of leaf twister were
identified as initial appearance of leaf curling, twisting, chlorosis and
abnormal elongation of the pseudo stem and with time withering and
decaying of whole leaf blades. Rotting of basal plates and appearance of
white mycelium are unique to the basal rot disease. This research was carried
out to provide biological alternate for harmful fungicides by using different
species of Trichoderma. Different combinations of the pathogen and bio agents such as F. oxysporum f. sp. cepae (Fo): Trichoderma viride (Tv) at
1:1, 1:2, 1:4, 4:1, and 1:0 as control were tested as treatments with five
replicates. F. oxysporum f. sp. Cepae was also tested with Trichoderma
harzianum with the same ratios. Similar experiment was also conducted for
C. gloeosporioides.The results showed that F. oxysporum f. sp. cepae: T.
viride (1:4), F. oxysporum f. sp. cepae: T. harzianum (1:4) and C.
gleosporioides: T. viride (1:4) yielded growth inhibition of 89.72%, 88.36%
and 92.52% compared with untreated control. Both species of Trichoderma
controls F. oxysporum f. sp. cepae efficiently, where as T. viridae is the best
to control the C. gloeosporioides than T. harzianum.
