Fresh leaves of ramtulsi (Ocimum gratissimum Linn.), Japanese mint (Mentha arvensis Linn.), marigold (Tagetes ercta Linn.), custard Apple (Anona squamosa Linn.), neem ( Azadirachta indica A. Juss), along with small cut pieces of bulb of garlic (Allium sativum Linn.) and soap nut of ritha ( Sapinodus mukorossi Gaertn) were taken and then oven dried by keeping the leaves and small pieces
of garlic and ritha for at least 15 min. within temperature range of 45-500 C.
When the leaves, garlic and ritha becomes crispy, those were taken out and crushed in a grinder. The crushed powder was put in methanol and kept for 2 days allowing the methanol to extract the toxicants of the leaves, garlic and ritha.
The conical flask containing methanol with powder leaves, garlic & ritha were shaken periodically for better extraction. After 48 hours, the extract was decanted out and was dried in a vacuum desiccator. The dried extract was scrapped out with the help of a sharp blade and weighed. About 1gm and 1.5 gm scrapped dried materials were dissolved in 100 ml of water each separately so as to get the desired concentration of extract of 1.0 % and 1.5% respectively.
Testing of Mortality-
For testing the mortality of pests, different plant extracts thus prepared was sprayed on leaf bits of Datura kept on wet cotton swab in a petridish with the help of micropipette syringe and on each of the leaf bits, 20 mealy bugs were released. A definite amount of spray fluid was topically applied by the said syringe and care was taken so that the leaf was uniformly sprayed. After application, the petridish containing the sprayed leaves was kept for taking observation towards mortality after different intervals like 24, 48, 72, 96 & 120 hours. Since the sprayed leaves were kept on wet cotton swab, the leaves remain fresh until the last observation was completed. In each dose three replications were maintained and there was also a controlled petridish where the leaf bits containing mealy bugs were sprayed with water only. To be sure of their mortality, the test insects were turned upside down with a needle and those which did not respond or were moribund, were considered as dead.
The percentage of mortality was calculated using the formula:
Number of the dead insects X 100 Total number of insects treated
All the values were calculated using Abbott’s formula (Abbott, 1925) as given below. The data recorded for percent mortality of different treatments were subjected to statistical analysis using SPSS-10 in Windows version.
0 0
100 P P P
(P = Percentage mortality after treatment with plant extract &
Po = Percentage mortality in controlled treatment) Percentage of corrected mortality =
Results
A perusal to the experiment reveals that at both concentrations (1.0 % & 1.5 %), 24 hrs. after treatment Japanese mint had given the highest mortality i.e. 60.0 % &
53.3 % and reached 99.9% mortality after 96 hrs of treatment (from table -1). No mortality was recorded in custard apple in both concentrations after 24 h of treatment and its mortality reached up to 20.0 % at 1.0 % and 40.0% at 1.5 % concentration after 120 h of treatment. No mortality was recorded in case of controlled treatment.
After 24 hrs of treatment garlic, soapnut of ritha, marigold , neem & ramtulshi recorded 44.7%, 25.3%, 26.7%, 20.0% & 7.7% and 53.3%, 46.7%, 33.3%, 33.3% &
20.0% mortality at 1% and 1.5% concentrations, respectively. Japanese mint was significantly superior to all other treatments in both concentrations (1% & 1.5%) but same mortality (53.3%) was recorded in garlic at 1.5% concentration after 24 h of treatment.
Likewise garlic was also superior to soapnut of ritha, marigold, neem & ramtulsi in both 1.0 % & 1.5 % concentration. The rate of mortality increased with increase of different intervals up to 72 hours. At increasing of intervals of time, mortality also increased in the same fashion in different treatments of both concentrations.
Among the tested plant products assayed against mealy bug, custard apple showed lowest efficacy (20.6%) followed by ramtulsi (33.1%), tagetes (48.8%), neem (49.4%), soap nut of ritha (56.6%), garlic (68.9%) and Japanese mint (73.5%) on increasing order of overall efficacy (from table-2) . It also showed that plant extracts in 1.5 % concentration are better than in 1% concentration and refer 54.5% and 45.6% overall efficiency against mealy bug among the plant parts products being tested (Table-3).
Table 1 : Effect of some plant extracts at two different concentrations (1.0 and 1.5%) on the mortality of mealy bug (Ferisia virgata Cock.) at different intervals of treatment
Plant Extracts
Conc. (%) H-24 H-48 H-72 H-96 H-120 Mean
Garlic 1.0 44.66 (43.11)c
66.66 (54.76)c
86.66 (68.61)c
93.33 (75.00)c
99.99 (89.00)a
66.09
1.5 53.33
(46.89)b 73.33 (58.89)b
93.33 (75.00) b
99.99 (89.00)a
99.99 (89.00)a
71.75 Ramtulsi 1.0 7.66
(16.00)g 13.33 (21.39)i
20.00 (26.57)i
40.00 (39.23)h
40.00 (39.23)f
28.48
1.5 20.00
(26.57)f
25.33 (30.11)g
33.33 (35.24)g
46.66 (43.11)g
65.11 (53.76)e
37.75 Japanese
Mint
1.0 60.00
(50.77)a 66.66 (54.76)a
86.66 (68.61)c
99.99 (89.00)a
99.99 (89.00)a
70.42
1.5 53.33
(46.89)b 86.66 (68.61)c
99.99 (89.00)a
99.99 (89.00)a
99.99 (89.00)a
76.50 Marigold 1.0 26.66
(31.11)e 40.00 (39.23)f
46.66 (43.11)f
60.00 (50.77)f
86.66 (68.61)c
46.56
1.5 33.33
(35.24)d 46.66 (43.11)e
53.33 (46.89)e
66.66 (54.76)e
93.33 (75.00)b
51.00 Custard
Apple
1.0 0.00
(0)h
1.33 (6.66)j
5.33 (13.33)j
20.00 (26.57)j
20.00 (26.57)g
14.66
1.5 0.00
(0)h
20.00 (26.57)h
26.66 (31.11)h
33.33 (35.24)i
40.00 (39.24)f
26.43
Neem 1.0 20.00
(26.57)f
26.66 (31.11)g
46.66 (43.11)f
46.66 (43.11)g
80.00 (63.43)d
41.46
1.5 33.33
(35.24)d 40.00 (39.24)f
66.66 (54.76)d
86.66 (86.61)b
99.99 (89.00)a
57.36
Ritha 1.0 25.33
(30.11)e 46.66 (43.11)e
66.66 (54.76)d
66.66 (54.76)e
93.33 (75.00)b
51.54
1.5 46.66
(43.11)c 53.33 (46.89)d
66.66 (54.76)d
86.66 (68.61)d
99.99 (89.00)a
60.47
Mean 30.83 40.32 50.34 59.06 69.64
SE (m) 0.79 0.71 0.80 0.74 0.64
CD at 5 % 2.28 2.05 2.32 2.14 1.84
* Numbers in parenthesis represent percentage of corrected mortality
Table 2 : Overall mean mortality percentage of mealy bug (Ferisia virgata Cock.) at both concentrations (1.0 % and 1.5 %) by seven plant extracts at different intervals of treatment
Plant extract H-24 H-48 H-72 H-96 H-120 Overall (%)
Garlic 45.00 56.83 71.80 82.00 89.00 68.92
Ramtulsi 21.29 25.57 30.91 41.17 46.50 33.12
Japanese Mint 48.83 61.69 78.80 89.00 89.00 73.46
Marigold 33.18 41.17 45.00 52.77 71.81 48.78
Custard Apple 0.00 16.62 22.22 30.95 32.59 20.56
Neem 30.91 35.17 48.94 55.86 76.22 49.42
Ritha 36.61 45.00 54.76 61.69 82.00 56.61
Std. Error (m) 0.56 0.50 0.57 0.52 0.45
Table 3 : Overall mean mortality percentage of mealy bug (Ferisia virgata Cock.) in two different concentrations (1% and 1.5%) by seven plant extracts at different intervals of treatment separately
Conc. (%) H-24 H-48 H-72 H-96 H-120 Overall (%)
1.0 28.24 35.86 45.44 54.08 64.42 45.61
1.5 33.42 44.77 55.25 64.05 74.86 54.47
Std. Error (m) 0.30 0.27 0.30 0.28 0.24
* H-24, H-48, H-72, H-96, H-120 represents mortality % after 24, 48, 72, 96 and 120 hours of treatments respectively in Table-1, Table -2 and Table-3.
Discussion
The insecticidal properties of the extract of Mentha aquatica and Mentha longifolia were found against Sitophilus oryzae infesting store grain of wheat, rice and maize (Perrot, 1944). Also some extracts of Melia azadirach, Myrtus comnumis, Mentha longfolia, Pegnum larmala and Cymbapogan citrates acted as insecticides causing various degree of mortality as well as repellency (Saljoqi et al. 2000)
In the present study the extracts of Mentha arvensis both at 1.0 % & 1.5 % conc.
registered highest mortality among all the treatments. In a laboratory evaluation Japanese mint (Mentha arvensis Linn.) gave 100% mortality 96 hrs after treatment at 1.5 % conc. and 120 hrs. of treatment at 1.0% conc. and it was significantly better among five treatments for mealy bug (Ferrisia virgata) (Gupta et al. 2007).
The extracts of Ocimum gratissimum and Mentha aquatica also proved having insecticidal property against DBM (Plutella xylostella) and Formica ruffa in Democratic Republic of Congo (MashiMango et al.1990). The aerial parts of
Japanese mint are also known to eradicate external parasites like lice, pleas, bugs and flies and 100% mortality was recorded by using extracts of Mentha longifolia against Sitophilus oryzae in wheat after 48 hours of treatment (Melkani et al.
2009). As per the present experiment, the mortality observed with the use of extracts of garlic was 44.66 to 99.99 % at 1.0 % conc. and 53.33 to 99.99% at 1.5 % concentration. The extracts of Alium sativum (garlic) at 2 % concentration agreed nymphal cotton mealy bug (Phenacoccus solenopsis) on shoe flower plant (Hibiscus rosa sisnensis) gave 72 % mortality after 24 hours of treatment (Bhattarai, 1991). This confirms the findings of the present experiment.
In the present study mortality of Mealy bug (Ferrisia virgata) by soap nut of ritha extracts was recorded 93.3 % and 99.9%, 120 hours after application of 1.0 % & 1.5
% concentrations, respectively. Therefore, the observations of the present study have similarity with the earlier workers.
It was reported that a saponin fruit extract from Saponidus emarginatus showed toxicity against adults of the greenhouse whitefly Triaburodes vaporium (Hemiptera, Aleyroridae) (Porras & Lopez–Avila, 2009) and complete methanolic extracts from fruits have shown larvicidal and morphological alternations effects on mosquito Acdes aegypti (Diptera, Culicidae) ( Ferreira Barreto et al. 2006).
Another ethanolic fruit extracts from Sapindus mukorossi also showed anti coleopteran activity against pest of store grains (Sitophilus oryzae) (Coleopteran : Curculionidae) and also against Pediculus humanus (Phthiraptera : Padiculidae) (Rahman et al. 2007).
Several parts of plants viz. neem, pongamia, Indian privet, adathoda, chrysanthemum , turmeric, onion, garlic, ocimum, custard apple, ginger and some other plants acted as insecticidal plants which can be used in insecticide preparation (Singh and Saratchandra, 2005). Most plant species used for plant protection exhibit insect deterrent properties rather than insecticidal effect. It indicates that in some way those compounds inhibit normal development in insects. It acts as deterrent in the form of insect growth regulators (IGR), feeding deterrents, repellent and confuse ants. Antifeedent and repellent activity have been evaluated for some of the plants. A true antifeedent gives insect the opportunity to feed on the plants, but food intake is reduced until the insect die from starvation (Saxena, 1987). The growth regulators cause abnormality in metamorphosis and the insects suffering from malformations may become sterile or even die.
The present findings may be compared with the earlier study conducted in different parts of India and abroad with extract of other four tested plants like marigold, neem, ramtulshi & custard apple against Ferrisia virgata. However, it was quite more or less apparent from present study that most of the plant
extracts tested herein had shown good insecticidal properties and caused mortality, varying from 1.3 % to 99.9%.