Potato et al (2011) had found disease intensity

Potato variety cardinal was grown in the
experimental plots supplied with required amount of fertilizers, irrigation and
intercultural operations. The plants were started to spray just after the
initiation of the disease in the vicinity of experimental field. Locally
available fungicides Sectin (Fenamidone and Mancozeb (10%+50%)), Dithane M45
(Mancozeb), bio-control agent Trichoderma
viridae and cow urine were applied at different time intervals. Control
plot was maintained with only spray of water.

 Disease
intensities were calculated at different growth stages and the average was
taken for each treatments. Tuber yield of potato and average total yield per
plot were  taken and calculated in terms
of kg per meter sq. Average weight of tuber (in grams) and average number of
tubers per plant were also calculated.

There was high incidence of disease in
control plot i.e. 37.33% followed by plot treated with cow urine, Trichoderma viridae , Dithane M-45,
Sectin + Dithane M-45 and finally Sectin i.e. 32.5%,29.43%,28%,21.16% and
17.16% respectively.

All the control agents were applied in the
interval of 15 days. Application of control agent significantly reduced the
incidence of late blight on potato as compare to control. Maximum disease was
controlled by application of Sectin (at the rate of 0.5%) i.e., 54.06%. Sharma et al (2011) had found disease intensity
in Sectin sprayed plots was lower as compared to other plots sprayed with other
chemicals and unsprayed control plots i.e. among the high efficacious
fungicides; Sectin was most effective in controlling the disease.

Dithane M-45+Sectin combination also shows
that it was a good control agent for controlling the late blight disease i.e.
Dithane M-45+ Sectin (alternately used) treated plot shows 48.3% control and Dithane
M-45  solely treated plot shows controls
33.02% .Shrestha (1989) also reported that fungicide Dithane M-45 was
found  effective in reducing the severity
of late blight disease on potato. The maximum disease was controlled in all the
varieties of potato when Dithane M-45 was applied at the rate of 0.5% at 4 days
interval. But under most favorable climatic conditions and high inoculums
pressure it failed to protect the crop from the attack of disease.

In this experiment Trichoderma sprayed plot give average result in controlling the
disease i.e.21.16% where as Sharma et al
(2011) had concluded that there was no significant difference between Trichoderma sprayed and unsprayed check
plots, thus this experiment helps to weaken his conclusion.

 Minimum disease was controlled (12.93%) with
cow urine.

The yield of potato tubers was observed
negatively correlated with that of the late blight incidence, after all no
symptoms were seen on the harvested tubers.As seen in the table, the mean potato yield in Sectin+Dithane M-45 treated plot was found statistically
highest/superior i.e. 3.527 kg/plot followed by the at par results on plot
treated with Sectin (3.235 kg/plot) and Dithane M-45 (2.965kg/plot); while Trichoderma viridae treated plot yielded more (2.637 kg/plot) than
the plot treated with cow urine and control, found statistically poor that is
2.065 kg/plot and 1.722 kg/plot respectively. As the incidence
increased, the yield was decreased and vice versa. Sectin and combination of
Sectin + Dithane M-45 were found much superior as compare to other chemicals
and other control agents. Sharma et al.
(2011) also reported that the tuber yield increase was highest in Sectin
sprayed plot.

 Along
with yield the average tuber size in Sectin+ Dithane M-45 treated plot was also
larger i.e. 64 g, followed by the at
par results on plot treated with Trichoderma
viridae (54.8 g), Sectin (53.8 g) and Dithane M-45 (49.2 g); while plot
treated with cow urine (43.4 g) and control 
(42.2 g) was found statistically inferior.

 In the
same manner there was not any significant difference in the average number of
tubers per plant in various treated plot. Plot treated with Sectin+ Dithane
M-45 gives maximum number of tubers (11.75units), Dithane M-45 (11.62 units), Trichoderma viridae (11.55 units), cow
urine (11.35 units), Sectin (11.2 units) and control (11.15 units) respectively
in descending order