Gardening the Bhutanese Way

Wednesday, March 30, 2016

Efficacy of Bio-repellents on pest control in cabbage


An overall view of the trial plot


1.  Background


Vegetable production during summer  in the cooler regions and during winter in the warmer belts of the country is a sole activity contributing to the livelihood of many dwelling in farming community.  Among many, the most important cash crop is cole crops which includes Cabbage, Cauliflower and Broccoli.
Despite the challenge taken up by the farmers in enhancing production and opting to vegetable commercialization, they are always confronted with problems like the menace inflicted by pests and diseases. One rampant pest curtailing cole crop production is the infestation of Cabbage White Butterfly(Pieris brassicae).
This has however led to the use of hazardous pesticides. Though the use is on a limited scale at the moment, it might  lead to its indiscriminate use over the years. Then the danger of the pests developing resistance to the pesticides  and the problem of pest resurgence coupled with the residual effect that it would leave on soil, and the corresponding environmental damage might ensue if we resort to its indiscriminate use.

Therefore, a need to explore means of organic pest control is strongly felt. In line with this,  an effort in studying the efficacy and the economics of using such locally prepared bio-repellents as well as the ease with which the materials can be obtained in the locality is a prerequisite step  before recommending and or taking the technology to the farmers' field.

2. Objectives:

v  To identify the most suitable organic pest control measures keeping in view its efficacy, availability, economics and applicability in our local conditions against common and destructive pests.
v  To explore eco-friendly measures of pest control that would contribute to sustainable agriculture.


3. Materials & Methodology

The trial was carried out in RCBD (Randomized Complete Blovk Design) experimental design with 5 treatments including control and 3 replications. In total, there were 15 plots of 6 sq. m. dimension each. The plants were indented at a spacing of 30*45 cm. The trial area of 90 sq. m. encompassed a total plant population of 585.

Nursery Raising, dated 24/02/15
Seedlings ready to be transplanted, dated 8/04/15

A total of 5 treatments viz.; Garlic brew, stinging nettle & cow urine extract, wood vinegar and Artemisia leaf extract including control were used. The treatment application started a week after transplanting and continued on weekly basis.  The method of application resorted to was foliar application with knapsack sprayer. A total of 9 applications were sprayed until it was stopped a week before harvesting.

The plants were visually inspected for the incidence of pests as well as the insect feeding damage on weekly basis simultaneously with the treatment application. The total number of plants with insect feeding damage and total yield per plot were also recorded ultimately.
Pests observed: Diamond Back moth (left); Cabbage white butterfly larvae (right)

Visual inspection of plants for insect feeding damage





3.   Result & Discussion:
The crop reached its harvestable maturity in a span of 114 days after sowing. The details of the recording are as illustrated in the table 1.
Table 1: Observation on plants infested by insects and Yield
Treatments
No. of plants with insect feeding damage
Yield(Kg)
R1T1
4
20.8
R1T2
2
28.66
R1T3
5
27.8
R1T4
2
21
R1T5
6
18.14
R2T1
2
18.96
R2T2
0
17.52
R2T3
5
15.84
R2T4
3
18.06
R2T5
10
16.52
R3T1
2
19.36
R3T2
0
20.98
R3T3
8
16.96
R3T4
1
15.52
R3T5
5
17.5



Table 2: Yield/plots and yield/acre
Treatments
Avg. number of  plants infested/plot
 Avg.Yield(Kg)/ plot
Yield/acre(MT)cre(MT)
T1(Garlic brew)
2.67
19.71
13.14
T2( Stinging nettle & cow urine extract)
0.67
22.39
14.92
T3( Wood vinegar)
6
20.3
13.47
T4( Artemisia leaf extract)
2
18.19
12.13
T5(Control)
7
18.05
12
                 

The total number of plants infested was found to have inverse relation with the total yield. The number of plants infested was found to be lowest in T2 (stinging nettle and cow urine extract ) treated plots and accordingly the yield was recorded to be the highest in the said treated plots.

On the contrary, the control plots recorded the highest rate of infestation by pests which yielded the lowest productivity per unit area.

The harvested cabbage heads; without any major/severe pest attack.








Table 3: Pearson's Correlation

Yield
Yield

No. of infested plants
-.205

Pearson’s correlation indicated that the number of plants infested and yield are negatively correlated at Pearson’s correlation coefficient(r) of 20%.

Table 4: One-way ANOVA for the number of plants infested

Sum of squares
df
Mean square
F
Sig.
Between Groups
Within Groups
Total
88.000
27.333
115.333
4
10
14
22.000
2.733
8.049
.004

Total number of plants infested were highly significantly at 0.01 significance level between the treatments.  However, the treatments had minimal influence over the yield per unit area among the treatments.


4.  Conclusion.

It can be deduced from the trial that a combination of stinging nettle and cow urine extract proved to be the best treatment in warding off the commonly prevalent pests  with only 2 plants with feeding damage in one of the replications while 2 plots in the other 2 replications recorded zero infestation.
The treatment also did well in producing heads of better quality and in nourishing the plants for comparatively higher yields though there weren’t much significant variation in the yields among the treatments.
In contrast, the control plots recorded the highest rate of insect feeding damage of 21 and the corresponding decrease in the yield.
Therefore, it can be suggested that the use of stinging nettle and cow urine extract be encouraged in our farming system.
However, this conclusion is reached solely based on the trial data of only a single season and the reliability of the research findings is questionable until the results be reaffirmed by similar trials in the coming seasons.
One major drawback of such bio-formulations/repellents is its limitation in their storage life since it requires that the formulations be applied within 2 days of its preparation. This along with the frequency of application that it requires might hamper its adoption by the farming community where labour scarcity is an issue which is always on the ascend.

 

1 comment:

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