Bio-efficacy of botanicals and insecticides against whitefly, Dialeurodes kirkaldyi Kotinsky (Aleyrodidae: Hemiptera) in jasmine, Jasminum sambac

Introduction

Jasmine (Jasminum sambac L.) is one of the oldest traditional perfumed flowers cultivated by man and is considered as the 'Queen of fragrance' which belongs to the family Oleaceae (Kiran et al., 2017) [7] . It is an important flowering plants which are commercially grown for their scented flowers and used for oil production (El-Amir et al., 2020) [3] , perfumes and attars (Arumugam et al., 2002) [1] . India trades jasmine flowers to the adjoining countries like Sri Lanka, Singapore, Malaysia and Gulf countries. In South India, huge quantities of jasmine flowers are used by women folk for beautifying their hairs. Tamil Nadu is the leading state in jasmine production in the country. The least yield of jasmine flower production might be due to various reasons, among which the menace by insect pests is of fundamental consequence. There are about 50 diverse insect species belonging to more than eight orders harbouring fluctuated microhabitats of jasmine plants. The jasmine whitefly, Dialeurodes kirkaldyi (Kotinsky) (Aleyrodidae: Hemiptera) is one of the most significant pest of jasmine all over the world. It was first described on Jasminum grandifolium in 1907 from Hawaii (Kotinsky, 1907) [8] . The nymphs and adults of whitefly suck the sap from lower surface of the leaves and cause yellowing thereby minimizing the vitality of the plant. It invites sooty mould fungus thus photosynthesis will be affected and yield reduction occurs (Rabeena et al., 2020) [13] . Farmers depend mostly on insecticides for controlling whiteflies in jasmine. The decreased efficacy of pesticides and increased worries over their use in jasmine ecosystem have highlighted the need for identifying safer, more effective botanical and newer insecticide molecules for the management of whiteflies in jasmine. Hence, the present study was carried out to assess the efficacy of botanicals and newer insecticide molecules against whiteflies in jasmine.

Materials and Methods

A field trial was conducted in a farmer's field near Vallanad village, Thoothukudi district, Tamil Nadu, India. The experiment was conducted on existing jasmine crop of 1 ½ years old plant. Three rounds of foliar sprays were given at fortnight interval using battery operated knapsack sprayer. Pre-treatment observations on the incidence of whiteflies were recorded in each botanicals / synthetic insecticides treated plants. Post treatment counts were recorded on 1 st , 3 rd , 7 th and 14 th day after imposing treatment. Whiteflies population were recorded from 21 randomly selected leaves from top, middle and bottom of the bush and expressed as number of whitefly adults per leaf (Hemalatha, 2009) [4] . Randomized Block Design was adopted in each treatment, three plants and three replications were maintained for observation.

Preparation of botanical leaf and kernel extracts i. Notchi (Vitex negundo) leaf extract

The fresh leaves of Notchi, V. negundo were collected and dried under room temperature (25±2 °C) and then powdered. A total of 100 gram powdered leaves were soaked in 1.0 litre of petroleum ether (boiling range 60-80 °C) was shaken for 24 hours and kept under room temperature for 10 days. After 10 days, the extract was made upto 1000 ml and maintained as standard solution. At the time of spray, 50 ml of standard solution was added in 1000 ml of water and used for spraying (Karunamoorthi et al., 2008) [6] .

ii. Neem Seed Kernel Extract (NSKE)

A quantity of 50 g dried neem seed kernel was powdered and it was tied in a small muslin cloth bag and dipped in 100 ml of water and kept overnight for 12 hours and the suspension was separated. Then, 900 ml water was added to it and stirred well. The filtrate was used for spraying (Sathyan, 2015) [14] .

iii. Pungam (Pongamia pinnata) (Karanj oil) Pungam oil was purchased from the market and sprayed at the rate of 20 ml per litre after thorough mixing with the surfactant.

Rhizome powder of 300 g was added into 1000 ml of distilled water and kept for 24 hours. Then the solvent was filtered. At the time of spray, 50 ml of solvent was used (Shinthiya and Razak, 2017) [15] .

v. Wild sage (Lantana camara) leaf extract

One kg fresh leaves of wild sage, L. camara was dried at room temperature and then powdered. One litre of petroleum ether was added to the dried leaves under kept in shaker for 8 hrs. Then, the extract was filtered. The filtrate thus obtained was used for spraying (Deshmukhe et al., 2011) [2] .

The list of botanicals evaluated in the field experiments are furnished below.

Results and Discussion i. Bio-efficacy of botanicals against whitefly, D. kirkaldyi in jasmine

The results stated that the influence of the treatments, spray rounds and period of observations; interaction effectiveness was also significant (Table 1a-1c). The incidence of whitefly ranged from 2.00 (at 7 th day of 3 rd spray round on pungam oil treated plant) to 6.00 (at 14 th day of 1 st spray round in untreated check). Mean population of whitefly over spray rounds as well as period of observations confirm the most effectiveness of pungam oil 2 per cent recording the least population (2.44/ leaf) than all other treatments except the standard check, Profenophos 50 EC; able to reduce the whitefly population more than 50 per cent over untreated check. All other treatments including the standard check brought down the population by 31.94 to 48.01 per cent. The trend was almost similar at each round of spray, period of observations. All the treatments were able to reduce the low population of whitefly even after 7 th and 14 th day after 3 rd round of spray including untreated check.

Kumar (2007) [9] reported that pungam oil @ 2.0 per cent was effective in reducing the whitefly population followed by V. negundo leaf extract @ 5 per cent and NSKE @ 5.0 per cent (Fig. 1). The effectiveness of pungam oil @ 2.0 per cent for the control of jasmine pests revealed in the present study is confirmed by Ponsekha and Muthusamy (2016) [12] , with their laboratory bioassay as well as by the field studies reported by Merlin Kamla (2017) [10] in jasmine.

ii. Bio-efficacy of insecticides against whitefly, D. kirkaldyi in jasmine

The data on the bio-efficacy of insecticides against whitefly presented in The insecticide application provides an immediate solution to control the insect pests and seems to be the most important pest management tool in enhancing agricultural production. The study brought out the superiority of Imidacloprid 17.8 SL @ 0.30 ml/lit followed by Acetamiprid 20 SP @ 0.10 g/lit against whitefly on jasmine (Fig. 2). Imidacloprid 17.8 SL @ 0.30 ml/lit and acetamiprid 20 SP @ 0.10 g/lit belongs to the main group of nicotinic acetylcholine receptor (nAChR) agonists and exemplifying Active Ingredient of neonicotinoids. They inhibit synaptic transmission in insects (IRAC, 2009) [5] . Chloronicotinyl compound has good xylem mobility and it is found effective against sucking pests (Omkar Gavkare et al., 2013) [11] .

Conclusion

Considering the efficacy of different botanicals against whitefly, D. kirkaldyi in jasmine, pungam oil @ 2.0 per cent stood first effectively reducing the incidence of whitefly with 51.30 per cent reduction was followed by notchi (V. negundo) leaf extract @ 5.0 per cent and NSKE @ 5 per cent. Among the insecticides, Imidacloprid 17.8 SL @ 0.30 ml /lit, Acetamiprid 20 SP @ 0.10 g /lit were found to be effective against whitefly with 82.63 and 79.44 per cent reduction, respectively. The results from the present investigation can provide valuable information with special emphasis on selection of insecticides as well as development of pest forecast models towards the development in IPM module in jasmine.

References

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