Document Type : Research Paper

Authors

• Elena Hosseini ¹
• Shahram Aramideh ²
• Abbas Hosseinzadeh ³

¹ PhD Student in Entomology, Department of Plant Protection, Faculty of Agriculture, Urmia University

² Associate Professor of Department of Plant Protection, Faculty of Agriculture, Urmia University

³ 3. Assistant Professor Department of Plant Protection, Mahabad Branch, Islamic Azad University, Mahabad. Iran

Abstract

    Background and objectives: Alfalfa, Medicago sativa L. from the leguminous family, is among the best fodder plants due to its richness in protein, calcium, vitamins, palatability, and low percentage of cellulose, which is called green gold. Alfalfa is the first crop that was domesticated and cultivated as fodder. Alfalfa leaf weevil, Hypera postica Gyllenhal, is one of the important pests of alfalfa fields in Iran. Its main damage is related to the larval stage, caused by feeding on the plant leaves, especially in the first cut. The most common method of controlling this pest is using chemical pesticides, which cause pesticide residues, the death of natural enemies, resistance, environmental pollution, and the emergence of secondary pests. Therefore, research is necessary today to replace other compounds, such as botanical pesticides. In this research, the effects of Neemarin extracted from the neem plant (Azadirachta indica A. Juss) and Matrine extracted from Sophora flavescens (Ait.) on second instar larvae and adult insects of alfalfa weevils were investigated in laboratory and field conditions.
Methodology: Laboratory studies were conducted in a completely randomized design, and field evaluation was conducted in the form of completely randomized blocks in the spring of 2023 in Naghadeh City. The botanical insecticide Matrine, with its commercial form on Rui Agro and Neemarin extracted from the neem plant, was used in the experiments. Bioassays were performed on the second instar larvae and adults by immersing the host leaf in the concentrations of both compounds, and the mortality was recorded 24 and 48 hours after the treatment. After determining the LC50 and LC25 of Matrine and Neemarin, their mixed effects on second-instar larvae and adult insects were evaluated. This study used treatments including LC50 Matrine, LC50Neemarin, LC25 Neemarin + LC25 Matrine, and the control treatment on second instar larvae and adults. Also, the effect of sublethal concentration (LC25) on metamorphosis (transformation of the larval stage to pupa and transformation of the pupal stage to the adult insect) was studied. The field experiments were analyzed in three alfalfa fields treated with Neemarin (2000, 3000, and 4000 ppm), Matrine (200, 400, and 600 ppm), and control (water). Each treatment was evaluated in three repetitions using the Henderson-Tilton method.
Results: The results of probit analysis showed that calculated LC₅₀ of the two botanical insecticides, Neemarin and Matrine on adult insects and second instar larvae of alfalfa after 48 hours were 544.65, 50.23, 45.86 and 3.76 ppm, respectively. Also, the effect of LC₂₅ of both biopesticides showed that the greatest inhibition in the transformation of larva to pupa is related to Neemarin (30%) and in the transformation of pupa to adult is related to Matrine (51.50%). In the field experiments, the highest mortality in adults was observed in the concentration of 600 ppm Matrine with 53.33% and in the second instar larvae related Neemarin (2000 ppm) with 27.33% mortality.
Conclusion: These investigations showed that Matrine pesticide has a higher lethality effect than Neemarin in laboratory and field conditions on adults and second-instar larvae of alfalfa leaf weevil. The effect of a sublethal dose of Neemarin on pest metamorphosis was more effective. Therefore, both pesticides can be used to manage this important pest.

Keywords

• Growth inhibition
• lethality
• non-chemical control
• alfalfa

Main Subjects

• Biological effects of essential oils and extracts