Comparative Effects of Two Methanolic and Acetonic Extracts of Tomato Leaf on Bracon hebetor Say (Hym.: Braconidae)

The use of plant extracts is important in integrated pest management programs. Extract is a solution containing all useful plant substance including tannins, mosilajs and essences. Plant extracts can be alternatives for today’s pesticides. Pesticides are potentially hazardous to humans, adverse health effects of them often can occur after exposure and are called acute and chronic effects. The negative effects of pesticides are the ability of them to bioaccumulate and biological magnification. Biological control agents are new compounds that can control insect pests without negative effect on environment and food safety. If these plant compounds to be safe for natural enemies in addition to be effectiveness against pests, they will be efficient. Application of Biological control can minimize pesticides exposure and thus reduce hazard of them. Biological control agents are new compounds that can control insect pests without negative effect on environment and food safety. Bracon hebetor Say (Hym: Braconidae) is one of the most important biological control factors on farms, orchards and forests of the country widely perceived to be in nature and can be effective in controlling larvae of leprose winged pests at acceptable economic level.

This study was done at Tabriz Azad University Iran, during 2018. It was carried out based on complaitly randomized design with five replications and each test comprised a minimum of five log spaced concentrations and water as the control. Two extracts used in this experiment that were methanolic and acetonic extracts of tomato leaf. Extraction was carried out by using methanol and acetone as solvents. leaves of tomato collected, well washed with distilled water, air dried in shadow then used for extraction. Bioassays were conducted against male and female adults of B. hebetor. The level of adult bees’ death was registered after 24 hours. The results were registered and the data were analyzed for obtaining LC50 and LC25 using software SPSS and Probit program. In the following experiment, the sublethal effects of concentration of LC25 of the extract on the B. hebetor biologic parameters in combination with water were examined. Daily schedules of mortality and fecundity were recorded and used to calculate life table parameters. Variance and standard error were measured using the Jack-knife technique. Analyses of variance and the means were compared by the Tukey test, using SPSS software program, and the figures were drawn by software Excel.

In this study, response of B. hebetor, was studied to acetonic and methanolic extracts of tomato leaf that treated by LC25 of extracts and then the life history parameters were compared. The average number of eggs laid and fertility eggs in order to control and metanolic and acetonic extracts 39.49, 46.93, 23.11 and 28.04, 28.67 and 17.33 respectively. The greatest number of offspring produced per female was observed in the treatment of methanolic. The number of eggs laid in acetonic treatment is affected more than other treatments. The Adult longevity of B. hebetor in control and treatment with methanol and acetone was 19.5, 19.12 and 18.12 respectively. The highest adult longevity was seen in control and the lowest longevity was seen in acetone. The sex ratio (female / (female+male)) was in control and methanolic and acetonic extracts, respectively 0.55, 0.94 and 0.57. The sex ratio in the methanolic treatment was highest, indicating the female is more in comparison with male oriented, which means less negative effects of methanolic extract. The lowest sex ratio was in control (0.55). The life expectancy of wasps, which were under treatment by acetonic extract, was significantly lower than control and methanolic treatment.

Our results detected that the diverse of extracts had different effects on biological parameters of B. hebetor. Investigation of sublethal effect of pesticides have a great important in IPM programs. This effect does not demonstrate the insect death, but decrease their populations in next generations. Thus, the evaluation of sublethal effect in insect behavior such as parasitoids is essential for the development of new strategy.