تخمین‌های دقیق و سریع انبوهی جمعیت سرخرطومی برگ یونجه Hypera postica (Col., curculionidae)

Alfalfa Medicago sativae L. is the most important forage crop and alfalfa weevil, Hypera postica L. (Col., Curculionidae) is the most important it's pest. Precise estimates of population rely mainly on time-consuming absolute sampling methods, while for decision making purposes a rapid estimate by a relative sampling method is required. If one can obtain a strong correlation between absolute and relative estimates, then a rapid and at the same time precise estimate is possible which satisfies requirements of both research and pest management purposes. In this study an absolute method i.e. quadrat with a determined area and a relative method of standard sweep net were used for estimating population parameters of Alfalfa weevil. The study was carried out in a 2000 m2 alfalfa field at the Research Station of Faculty of Agriculture, University of Tabriz in two years of 2023 and 2024. The mentioned field was divided to a grid of 20 squares, 100m2 each (10m*10m), and weekly samples were collected from all stages (larvae, and adults) using the two methods from mid-March until the first hay harvest. Sampling unit was a square quadrat (0.5m*0.5m) which a couple of samples per 100m2 were obtained and all larvae and weevils were counted on two plants within each quadrat. Relative estimates also were obtained per 100m2 by four sweeping effort. Both spatial and temporal relations between counts of the two methods were studied by a linear regression forced from origin which were drawn to relate counts per sweep to a meter square of area. For temporal relationship, counts of all units were summed over a date. A strong relationship was observed between estimates of the two methods at both years (F=2978.06, df=1, 379, P<0.0001, and F=3994.09, df=1, 399, P<0.0001 for spatial correlation and F=450.06, df=1, 18, P<0.0001, and F=509.69, df=1, 20, P<0.0001 for temporal correlation of years 2023 and 2024 respectively). The results also revealed that 29.2 and 27.0 sweeping effort corresponds counts of the quadrats per 1m2 of alfalfa field and coefficient of determination was 0.877 and 0.909 for years 2023 and 2024 respectively. Overall, the results show that sweep net may provide precise and meanwhile rapid tool for population estimate of alfalfa weevil.