عنوان مقاله [English]
Natural and human hazards arising from the use of chemical pesticides to reduce pest damage are significantly increased. In this way, tend to use alternatives with similar efficacy and less risk like plant to control pests has increased. Therefore, it seems that plant compounds can be used as alternatives to chemical insecticides to protect agricultural products in the future. These compounds have no harmful and negative effects on nature and are safer than chemical insecticides; they decompose rapidly, do not remain in soil and water and have no effect on non-target populations. One of the important agricultural products around the world is potato and a major pest of it around the world and in Iran that damage the product is Colorado potato beetle, Leptinotarsa decemlineata (Say). Nowadays chemical control is the most common method to control of this pest but causes resistance. According to the Colorado potato beetle resistant to conventional chemical pesticides for controlling them, in recent year tendency to use insecticide with plant origin become more for this pest.One of the most important plant compounds are essential oils. Due to the low risk of essential oils to humans and the environment and their insecticidal effect, we motivated to investigate the insecticidal effects of three important medicinal plants on Colorado potato beetle for reducing the environmental hazards arising from the use of chemical insecticides.
Materials and methods
Three insecticides thiamethoxam, diniteforane, imidacloprid were bought and three essential oils Satureja khuzistanica Jamzad, Ocimum basilicum L. and Mentha spicata L. were gathered in spring then dried in shade at room temperature and for later use in special plastic bags were stored at -24 ° C. With Clevenger essential oils were extracted. In the spring and summer 4th instars larvae of Leptinotarsa decemlineata Say from potato fields of Ardabil plain collected. Investigation against this pest in a completely randomized block design with four replications under field conditions was done. Mortalities were recorded at 1, 3, 5, 7, 9, 11, 13 and 15 days after spraying insecticides and essential oils. The control plants were treated with water. Data analysis was done in SPSS16 software and the mean of the data was compared with Turkeys' test.
Results and discussion
Result showed that in this study thiamethoxam had greatest effect on fourth instar larvae of Colorado potato beetle. In 15 cc a.i./ha of thiamethoxam in the environment after 15 days 95 % mortality happen . Imidacloprid and diniteforane after 15 days have 68 and 73.6 percent mortality respectively. Imidacloprid and thiamethoxam are two most common Colorado potato beetle insecticides that are used by farmers. Diniteforane is not so common insecticides in country. Also investigated showed that essential oil of S. khuzistanica had greatest effect on fourth instar larvae of Colorado potato beetle. In 15 cc a.i./ha of S. khuzistanica in the environment after 15 days 90.2 % mortality happen . O. basilicum and M. spicata after 15 days have 48 and 46 percent mortality respectively. Data showed that essential oils are highly selective and because of their effect (actopamin receptor) usually have no adverse effect on mammals. These compounds in contrast to synthetic carbamates, organophosphouros, and pyretroid that have adverse effect on the environment and people are safe for the environment.
Therefore, using plant material is effective step for reducing environmental risk of chemical insecticides that used for agricultural crop in country. In order to reduce the environmental hazards caused by the use of chemical pesticides, we can say:
1- Limit the use of chemical pesticides.
2. Use plant materials that are safe for humans and creatures.
3. Promote and educate the use of these compounds among farmers.
Thereby researcher thanks and appreciated from the Faculty of Agricultural Sciences of University of Mohaghegh Ardabili for doing this project.