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The biocidal activity of castor oil plant (Ricinus communis) in controlling the whitefly Bemisia tabaci (Genn) (Homoptera: Aleyrpdidae) was examined. Castor oil was extracted from seeds using different solvents, hexane, acetonitril and methanol. Assays were performed with adults and larvae. Mortality of the pest increased with increasing concentrations of castor oil. The lethal concentrations of the castor oil extracts was higher for adult fly than the immature stage. The insecticidal values of castor oils were compared with other formulations based on Azadirachtin (neemix, 4.5% EC) and Pyrethrum 5% SC. Emulsions of castor seed oil gave effective control against the whitefly Bemisia tabaci (Genn). Key wards: Ricinus communis, oil, Azadirachtin, Pyrethrum, Bemisia tabaci (Genn) INTRODUCTION Whitefly Bemisia tabaci (Genn) is a very important pest because of the damage they cause. Control methods using castor oil have been evolved and practiced with varying degrees of success (Abbas, 2003; Baldin et al. 2007). Many researchers have taken the Azadirachtin and pyrethrum for comparison in their work. Also in the present study they were used for comparison and to ascertain the activities of castor oil. Azadirachtin and Pyrethrum have a long history for use as insecticides. Azadirachtin exhibits good efficacy against key pests such as whiteflies, leaf miners, fungus gnats, thrips, aphids, and many leaf-eating caterpillars (Immaraju, 1998). Its use is recommended for insecticide resistance control, integrated pest control, and organic pest control programs. Over 400 species of insects have been shown to be susceptible to the neuroendocrine effects of azadirachtin, exhibiting classic symptoms of abnormal molts, larval–adult intermediates, mortality at ecdysis, and delayed molts, often resulting in greatly extended instar lengths. Many studies on a wide variety of insect taxa have allowed detailed descriptions of symptoms to be recorded that show consistency between all insects tested and an ED50 (effective dose for 50% of the population) of between 1 and 4 mg/g bodyweight (Koul and Isman, 1991; Mordue (Luntz) and Blackwell, 1993; Riba et al., 2003). Pyrethrum is one of the first insecticides with a century-long history of safe use (Katsuda, 1999). The active compounds of pyrethrum extract are six esters, commonly referred to as the pyrethrins. Most insects are still susceptible to pyrethrum at low concentrations, and its action is against a wide variety of different insect species (Silcox and Roth, 1994). MATERIALS AND METHODS Collection of the plant seeds and preparation of the plant oil Seeds of castor were collected from El-Minufiya Governorate during Nasr S. Khalil et al. 32 the summer of 2007 and 2008. The seeds of the Ricinus species were collected from dry fruits still on the plants, and were thus ready for further processing when collected. The oil of Ricinus communis was extracted and obtained by grounding the seeds using blender, then using different solvents for extraction starting with hexane for three weeks, after each week filtration was carried out and the oil was collected and obtained, so three samples of the oil were collected. After hexane, acetonitril was added and the oil was colleted. Repeating the experiment starting with hexane and then followed by methanol. So oils extracted by hexane, acetonitril, and methanol were obtained. Humidity and any water can be removed using calcium chloride anhydrous. Density of the three oils was calculated and found nearly the same and estimated as 0.97, 0.96 and 0.96 gm/ cm3 for the oils, respectively. Insect used Laboratory strain of whitefly Bemisia tabaci (Genn.) was obtained from Syngenta Agro Egypt Co., and maintained without exposure to insecticides for about three (3) years in the rearing laboratories of the Central Agricultural Pesticides Laboratory. The insects were confined with plotted cotton, which placed in an environmental chamber under conditions of 27 + 2 oC, 55 + 5% R H. and a photoperiod of 18 L: 6 D. The cotton plants (Gossyium hirsutum L., Giza-83) were grown in plastic pots containing mixture of peatmoss, sand and clay soil at the rate 1: 1 and maintained in another environmental chamber until the seedlings reached 15 – 20 cm high. Thereafter, these seedlings were introduced to the insects (Coudriet et al., 1985). Emulsifier and surfactant used 1Genapol OAO: white cloudy liquid, nonionic surfactant. 2Colsogen 4814: Browinish viscous liquid, anionic emulsifier of nC12 alkylbenzene sulphonate calsium salt in 2ethylhexanol. The emulsifier used is a mixture of these two compounds with a ratio 1: 3 Bioassay The bioassay method for obtaining concentration – mortality lines was previously described by Prabhaker et al. (1985). Attached cotton leaves were dipped for 5 Sec. in 100 ml of the desired concentrations of each insecticide and allowed to dry. Twenty adult whiteflies were exposed to the treated leaves confined in small cages (by an aspirator). Mortality was recorded 48 hrs after treatment. At least 5 concentraions were tested for each insecticide, and each test replicated 5 times. The treated leaves with the adults were kept at constant laboratory conditions of 27 + 2 oC, 55 + 5% R H. and a photoperiod of 18 L: 6 D. The data were analysed statistically using probit analysis. Commercial botanical insecticides formulations used: Neemix 4.5% EC (W/V): (formulated by Certis biopesticides company-USA Pyrethrum 5 % SC (W/V): (formulated by Agropharm) RESULTS AND DISCUSSION Extracts of castor (Ricinus communis) seeds prepared using various solvents, hexane, Acetonitrile and Methanol, were studied against the whitefly, Bemisia tabaci ( Homoptera: Aleyrodidae). The insecticidal values of castor oils were compared with other formulations based on Azadirachtin (neemix 4.5% EC) and Pyrethrum (Reptide 5% SC). The current work was undertaken to establish the effectiveness of the crude castor oils as an insecticide against whitefly. The crude oils were treated Biocidal activity of some castor extracts against the whitefly Bemisia tabaci 33 with an emulsifier to facilitate its mix with water. It formed an emulsion directly when mixed with water. In addition, nonionic surfactants was used which preferred for best results. The nonionic surfactants are surface-active compounds, which do not ionize in water solution.The ratio of the surfactant to the emulsifier was 1: 3. The emulsifier content never exceeded 10% of the oil content by any way to not affect on the results obtained. Water was used in our investigations as a preferred carrier. A direct spray was used so that upper and lower leaf surfaces are contacted. The spray was applied in a manner to provide complete and uniform coverage of infested plants. The data for mortality of Azadirachtin (neemix 4.5% EC), Pyrethrum 5% SC and crude castor oils are shown in Tables 1 to 5. Tables 6 to 10 show the mortality related to the active ingredient percentage and Figures 1 to 5 show their regresion lines. Table 1: LC50 and data analysis for Neemix 4.5 % (W/V) against white fly Bemisia tabaci Larval instar LC50 (mg/L) 95% confidence limits (mg/L) Slope ± Standard Error (SE) Chi square (χ) Lower Upper 1 Instar 1.12 0.15 2.46 1.70±0.16 20.45 2 Instar 1.76 1.49 2.03 2.34±0.24 0.08 3 Instar 2.12 1.71 2.63 1.27±0.14 2.59 4 Instar 4.34 3.33 6.29 1.11±0.20 3.37 Table 2: LC50 and data analysis for Pyrethrum 5% SC (W/V) against white fly Bemisia tabaci Larval instar LC50 (mg/L) 95% confidence limits (mg/L) Slope ± Standard Error (SE) Chi square (χ) Lower Upper 1 Instar 1.86 1.50 2.22 1.77±0.21 3.77 2 Instar 3.48 2.67 4.79 1.10±0.19 0.42 3 Instar 4.05 2.42 11.08 1.27±0.15 6.56 4 Instar 5.47 3.22 28.26 1.81±0.22 3.85 Table 3: LC50 and data analysis for castor oil seed extracted by acetonitrile ) against white fly Bemisia tabaci Larval instar LC50 (mg/L) 95% confidence limits (mg/L) Slope ± Standard Error (SE) Chi square (χ) Lower Upper 1 Instar 0.50 0.36 0.65 2.92±0.24 10.78 2 Instar 0.71 0.48 0.98 2.49±0.18 13.94 3 Instar 1.47 0.95 2.14 2.50±0.19 9.82 4 Instar 3.01 1.75 5.55 2.47±0.23 4.98 Table 4: LC50 and data analysis for castor oil seed extracted by methanol against white fly Bemisia tabaci Larval instar LC50 (mg/L) 95% confidence limits (mg/L) Slope ± Standard Error (SE) Chi square (χ) Lower Upper 1 Instar 0.35 0.22 0.46 2.45±0.24 8.31 2 Instar 0.54 0.46 0.62 2.29±0.18 5.26 3 Instar 1.63 1.00 2.56 2.45±0.19 12.39 4 Instar 2.49 2.16 2.86 2.29±0.22 1.23 Nasr S. Khalil et al. 34 Table 5: LC50 and data analysis for castor oil seed extracted by hexane) against white fly Bemisia tabaci Larval instar LC50 (mg/L) 95% confidence limits (mg/L) Slope ± Standard Error (SE) Chi square (χ) Lower Upper 1 Instar 0.84 0.62 1.11 2.59±0.18 11.05 2 Instar 1.69 1.08 2.62 2.49±0.19 11.66 3 Instar 2.56 2.12 3.15 1.42±0.15 3.30 4 Instar 3.79 3.19 4.60 1.77±0.21 0.66 Table 6: LC50 and data analysis for Neemix 4.5 % (W/V) against white fly Bemisia tabaci related to the active ingredient No Line name LC50 Lower limit Upper limit Slope Slope +/1 Nemix 1 instar 50,548 1,701 0,161 2 Nemix 2 instar 80,128 66,833 93,489 2,127 0,235 3 Nemix 3 instar 95,429 77,112 118,676 1,27 0,144 4 Nemix 4 instar 195,432 149,862 282,76 1,114 0,196 Table 7: LC50 and data analysis for pyrethrum 5% SC against white fly Bemisia tabaci related to the active ingredient No Line name LC50 Lower limit Upper limit Slope Slope +/1 Pyrethrum 1 instar 93,017 75,209 110,887 1,772 0,212 2 Pyrethrum 2 instar 174,303 133,718 239,164 1,101 0,194 3 Pyrethrum 3 instar 202,314 161,115 270,385 1,272 0,149 4 Pyrethrum 4 instar 273,621 226,719 350,441 1,81 0,22 Table 8: LC50 and data analysis for Castor Oil extracted by Acetonitril against white fly emisia tabaci related to the active ingredient No Line name LC50 Lower limit Upper limit Slope Slope +/1 Oil by acetonitril 1 instar 448,855 279,624 636,815 2,922 0,24 2 Oil by acetonitril 2 instar 640,979 374,615 999,853 2,442 0,188 3 Oil by aceto

Biocidal activity of some castor extracts against the whitefly Bemisia tabaci (Genn) (Homoptera: Aleyrpdidae)