اثرات حشره‌کشی فرمولاسیون کاربردی عصاره‌های گیاهی آویشن Thymus spp. و اکالیپتوس Eucalyptus spp. بر روی کرم غوزه پنبه، Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The use of plant pesticides has become a necessity due to the negative consequences of chemical pesticides on the environment. Chemical pesticides, which are widely used in agriculture, cause problems such as soil and water pollution, reducing biodiversity, and creating resistance to pests. These problems have led to increased awareness and attention to alternative and more sustainable methods such as plant pesticides. Herbal pesticides are produced from extracts obtained from plants. These extracts are mainly extracted from natural sources and different parts of plants such as leaves, roots, and flowers. One of the main reasons for paying attention to these extracts is their naturalness and compatibility with the environment. These pesticides are quickly broken down by microorganisms and natural processes in the environment and turn into harmless substances. This feature helps prevent harmful chemicals from accumulating in soil and water and reduces environmental risks. In this research, two Thymus spp. and Eucalyptus spp. were selected as plant sources for extracting secondary and effective metabolites. By using n-hexane solvent, extracts of two plants were prepared by the percolation method. The purpose of this extraction was to investigate the effect of different concentrations of the effective formulation of hexane extract on the mortality rate of the 3rd instar larvae of the cotton bollworm (Helicoverpa armigera) in laboratory conditions. The results showed that the use of different concentrations of hexane extracts of thyme and eucalyptus created a statistically significant difference in the mortality rate of 3rd instar larvae of cotton bollworm within 24 hours. In the study of the lethal effect of concentrations of 0.25%, 0.5%, 1%, and 1.5% of the effective formulation of the hexane extract of eucalyptus and thyme, the results indicated that due to the difference of the 95% confidence limits calculated after 24 hours in terms of There is a statistically significant difference in lethality. Therefore, the mortality rate of the 3rd instar larva of H. armigera at the lethal concentration of 50% (LC50) of the effective formulation of hexane extract of eucalyptus and thyme is 0.404% and 0.490%, respectively. Therefore, the effective formulation of hexane extract of Eucalyptus has more toxicity than the effective formulation of hexane extract of thyme against the 3rd instar larvae of cotton bollworm, H. armigera. These results show that the use of n-hexane solvent to extract plant extracts can lead to the production of natural and more effective pesticides. Therefore, the effective formulation of hexane extracts of thyme and eucalyptus, compared to the extracts extracted by other solvents, has a more lethal effect on the mortality rate of cotton bollworm larvae. These findings can help to develop more sustainable and environmentally friendly methods in pest management.