Effect of Different Solvent Extracts of Calotropis procera (Willd.) on Demographic Parameters of Bemisia tabaci (Genn.)

Cotton whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is one of the most critical pests of numerous agricultural crops including tomato especially under protected cultivation. The whitefly because of ingestion of phloem sap, secretion of massive honey dew that reduces both the quality of the tomato and the available leaf area for photosynthetic activities, and transmission of plant viruses is considered as destructive agent. Development of alternative methods for chemical compounds seems essential in pest management due to human health and environmental safety. Since plants are rich sources of active chemicals they may be a substitute for pesticides. Recent studies have shown that chemicals with insecticidal properties derived from plants are active against target specific species and are converted to non-toxic materials in environment. In the present study the effect of Calotropis procera (Willd.) R. Br. (Asclepiadaceae) extraction on demographic parameters of B. tabaci was evaluated. For this purpose four different extracts were prepared, using four different solvents (methanol, ethanol, acetone and hexan).The swallow wort plant, C. procera (Asclepiadaceae), is a shrub widely distributed in south of Iran (Haji Abad, Bandar Abbas, and Ourzoeiyh) and other parts of the tropics regions. The plant is erect, tall, large, branched and perennial with milky latex throughout. A large quantity of latex can be easily collected from its green parts. The essential oils and the extracts of this plant have insecticidal properties. Tomato seeds, Var. CH were planted directly in plastic pots filled with sterile plant growth media4 (BAGA; Dashte Sabz Atie Co. Iran). Cotton whitefly adults were collected from the Rafsanjan field and transferred onto 2-4 tomato leaves in a greenhouse. Adults of the same age were collected from red-eye pupae and moved to separate plant cages. These adults were used in all the experiments. The toxicity of C. procera for adults of cotton whitefly were assayed by the leaf-dip method. For bioassay, we applied five different concentrations in three replicates. Two clear plastic glasses (10 cm diameter, 15 cm height) were put together as a plant cage. The upper one was covered with a fine mesh and the lower one filled with distilled water. Two tomato leaves were dipped in the dilutions for 5s and put in each cage. After drying the treated leaflets, fifteen same age adults were released into the upper part of cage. Mortality was evaluated after 24 h and all of the experiments were carried out at 27±2 ºC, photoperiod of 16: 8 (L: D) and with the 50±5 % relative humidity. In this research, the effect of C. procera extraction with different solvents; acetone, ethanol, hexan, and methanol was studied on demographic parameters of B. tabaci on tomato. Data analyzed by Age-stage, two-sex life table analysis-MSChart software. The experiments were carried out in a completely randomized design (CRD) with at least four replications in controlled conditions. The collected data were analyzed by SPSS16 software and the means compared using Duncan’s test. The LC25 was estimated by probit analysis 2011 software. Graphs were drawn using SigmaPlot 11.0. Different biological parameters including pupa duration (F6,37= 4.49, P< 0.01) and female (F4,674= 23.649, P< 0.000) and male adult longevity (F4,575= 19.21, P< 0.000), sex ratio (male) (F4,10= 148.33, P< 0.000), sex ratio (female) (F4,10= 33.884, P< 0.000), oviposition period (F4,10= 13943.40, P< 0.000) and total fecundity/ female (F4,674= 31.450, P< 0.000),showed significant difference among extractions derived from various solvents of C. procera. The results showed that there are significant differences among treatments on net reproductive rate (R0 or NRR), intrinsic rates of increase (rm), finite rate of increase (λ), gross reproductive rate (GRR) and mean generation times (T) at the 5% probability level. The intrinsic rate of increase of the whitefly, in treatments control, and C. procera extraction by acetone, ethanol, hexan, and methanol solvents were 0.081, 0.030, 0.045, 0.054 and 0.043 respectively. All of the treatments compared with control reduced the oviposition period and the total number of eggs that laid each female. These two parameters were the least on acetone extraction of C. procera (0.59 and 3.093) and the highest on control (2.45 and 15.131) respectively. The results clearly indicate that the acetone and methanol extract of C. procera possesses many useful properties to control insect pests.