Field evaluation of fungicides against alternaria porri (Ellis) Cif., causing purple blotch of Onion ( Allium Cepa l. )

Sandovit (0.05%) was added to spray solution to

Results

avoid immediate runoff. Intensity of disease was

The results revealed that all the fungicides were

recorded by selecting five plants at random from

effective in management of the disease under high

each plot and 5 leaves were selected from each plant.

disease pressure.

The area covered by the disease was assessed using

0-5 scale (Mayee and Datar 1986) and expressed as

Field evaluation of effective fungicides against

Percent Disease Index (Shakyawar et al., 2014).

purple blotch of onion – 1 st season

Per cent disease index (PDI)

During the first season Cymoxanil 8% + Mancozeb

64% WP was significantly effective by recording

a least PDI of 23.99 as against 53.78 in untreated

control. This was followed by Mancozeb 70%

AUDPC (area under disease progress curve) was

WP, Pyraclostrobin 5% + Metiram 55% WG,

calculated according to the equation of Campbell

Pyraclostrobin 6.7% + Dimethomorph 12% WG,

and Madden (1990.

Metalaxyl- M 4% + Mancozeb 64% WP, Triademorph

AUDPC = ∑ ½ (Si + Si+1) x (ti+1-ti)

80% EC and Propineb 70 WP with PDI of 26.82, 30.43,

31.06, 31.11, 36.39 and 37.61 respectively. However,

Si = Disease intensity at time t i

the maximum yield of 40.56 t/ha was recorded in

Si+1 = Disease intensity at time ti+1

Mancozeb 70% WP followed by 37.67, 36.11, 35.18

and 34.20 t/ha in Cymoxanil 8% + Mancozeb 64% WP,

ti= Time when disease intensity was Si

Metalaxyl-M4%+Mancozeb64%WP,Pyraclostrobin

t i+1 = Time when intensity Si+1

5% + Metiram 55% WG and Pyraclostrobin 6.7% +

Dimethomorph 12% WG respectively as against

Harvesting and computing yield records

21.18 t/ha in untreated control.

The crop was harvested when the leaves turned

Cymoxanil 8% + Mancozeb 64% showed less

yellow and the top fall occurred. Bulbs harvested

AUDPC of 277.36 followed by Mancozeb 70%

from each plot were weighed and expressed as kg

WP, Pyraclostrobin 5% + Metiram 55% WG and

per plot. On the basis of yield per plot, the total bulb

Pyraclostrobin 6.7% + Dimethomorph 12% WG by

yield was computed and expressed in tonnes per

recording 283.08, 327.15 and 328.30 as against 613.19

hectare.

in untreated control.

Benefit: Cost Ratio (BCR)

Field evaluation of effective fungicides against

purple blotch of onion – 2 nd season

The economics of treatments was worked out by

considering the prevailing rates of inputs, produce,

The disease incidence was comparatively high

labour charges and expressed as an incremental

during the second season than the first season.

benefit cost ratio. Additional benefit due to increased

Mancozeb 70% WP was effective with a least PDI of

yield in each treatment over control was worked out

27.55 and yield of 38.86 t/ha as against a PDI of 61.59

based on the pooled yield of two years. The benefit

and yield of 20.16 t/ha in untreated control. This was

cost ratio was calculated using additional benefits of

followed by PDI of 28.09, 32.00, 32.56, 33.74 and 37.65

the produce and additional cost of the treatment.

and yield of 37.67, 35.18, 34.20, 36.11 and 32.80 t/ha in

Cymoxanil 8% + Mancozeb 64% WP, Pyraclostrobin

5% + Metiram 55% WG, Pyraclostrobin 6.7% +

Dimethomorph 12% WG, Metalaxyl- 4% + Mancozeb

Statistical Analysis

64% WP andTriademorph 80% EC respectively.

The PDI calculated and the yield data obtained were

Mancozeb 70% WP and Cymoxanil 8% + Mancozeb

analysed using ANOVA.

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