تأثیر تراکم‌های مختلف لارو سرخرطومی برگ یونجه (Hypera postica Gyllenhal.) بر روی عملکرد و اجزای عملکرد یونجه (Medicago sativa.L)

Alfalfa (Medicago sativa L.), a dicotyledonous plant from the Leguminosae family, is the fourth most extensively grown crop worldwide. Alfalfa is particularly valued for its high quality and palatability, as well as its nutritional reserves, which include various minerals, proteins, and even multiple types of vitamins. The alfalfa weevil (Hypera postica Gyllenhal.) is a significant pest of alfalfa in many regions of West Azerbaijan Province, Iran, and globally. To determine the relationship between larval density and damage level, an experiment using artificial infestation was conducted in a randomized complete block design with five treatments and four replications over two years (2014-2015). The treatments consisted of half-square-meter plots of the Hamadani cultivar. The experimental plots were located in a field in the village of Qurt Tappeh, Urmia, and were infested with various densities of first-instar larvae collected at the beginning of the season from different fields (Shoht, Chaldoran, and Urmia). The treatments evaluated were: uninfested control, 5 larvae per half-square meter, 10 larvae per half-square meter, 15 larvae per half-square meter, and 20 larvae per half-square meter. The traits studied included fresh yield, dry yield, and plant height. The analysis of variance results showed that the treatment effects on all studied traits were significant at the 1% probability level over the two consecutive years. For fresh and dry yields in both the first and second years, the lowest values (indicating the highest damage) were observed in the fourth and fifth treatments, while the highest values were recorded for the uninfested control treatment. Regarding plant height, the greatest damage in the first year was observed in the fifth treatment, while in the second year, the fourth and fifth treatments had the lowest heights. The uninfested control treatment had the greatest plant height in both years. Combined analysis over two years indicated that the effect of the year on plant height was significant at the 5% probability level, and the treatment effects on all traits were significant at the 1% probability level. Additionally, the interaction effect of year and treatment on fresh and dry yields was significant at the 5% probability level. Regression analysis was conducted to determine the relationship between larval density per square meter and the studied traits. The regression models for fresh yield, dry yield, and plant height as dependent variables were Y = 0.700 – 0.006X, Y = 0.245 – 0.002X, and Y = 43.973 – 0.272X, respectively.