Abstract
Purpose. To evaluate the effectiveness of different insecticides against pests on two-year old alfalfa grown for seeds.
 Materials and methods. The study was conducted in the experimental field of the Institute of Irrigated Agriculture of NAAS in 2017–2019. The filed experiments were laid out in split plots. The main plots (factor A) were for water supply conditions (no irrigation vs. irrigation); sub-plots (factors B and C) were for application of insecticides. Seeds were sown in wide rows with interrows of 70 cm.
 Results and discussion. When the two-year old alfalfa canopy (budding onset) was inspected before insecticide treatment, the average numbers of pests were as follows: alfalfa plant bug – 3.0 specimens/10 sweeps, alfalfa aphid – 20.0 specimens/10 sweeps, beet webworm – 3.0 specimens/10 sweeps, alfalfa weevil (imagoes/grubs) – 1.0/3.0 specimens/10 sweeps, and alfalfa seed weevil – 1.0 specimens/10 sweeps. Treatment 1 reduced the pest numbers in the canopy: alfalfa plant bug – by 70.0–93.3%, alfalfa aphid – by 93.0–97.5%, beet webworm – by 80.0–96.7, alfalfa weevil (imagoes/grubs) – by 60.0–90.0%/73.3–93.3%, and alfalfa seed weevil – by 76.0–94.0%, depending on the insecticide. Treatment 2 helped to reduce the pest numbers in the canopy. Insecticide containing active substances chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha was the most effective. The highest seed yield was achieved after treatment 1 with insecticide containing active ingredients chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha and treatment 2 with insecticide containing active ingredients chlorantraniliprole 200 g/L and lambda-cyhalothrin 50 g/L applied at a dose of 0.17 L/ha and 0.15 L/ha, respectively.
 Conclusions. The highest seed yield was achieved after treatment 1 with insecticide containing active ingredients chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha and treatment 2 with insecticide containing active ingredients chlorantraniliprole 200 g/L and lambda-cyhalothrin 50 g/L applied at a dose of 0.17 L/ha and 0.15 L/ha, respectively
Highlights
The primary objective of agriculture is the cultivation of crops, production of food for human and domestic animals
Insecticide containing active substances chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha was the most effective for pest control
The fumigation action of this insecticide had a negative effect on the numbers of pollinating insects, interfering with the formation of pods and seeds in generative organs and further affecting the plant performance
Summary
The primary objective of agriculture is the cultivation of crops, production of food for human and domestic animals. There are pests reducing crop yields intended for human consumption [1, 2, 3]. It is believed that the world produces a sufficient amount of agricultural products that meet the population’s needs, but the pestinduced damage to crops leads to severe economic consequences [4]. The yield can be significantly increased via timely prevention of losses caused by diseases, pests and weeds [5, 6, 7]. The total insect-induced losses in the yield have increased, and are largely due to changes in farming methods and cultivation technologies
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