بررسي تغييرات فصلي جمعيت ، روش هاي نمونه برداري و فضاي نمونه در شته هاي مهم گندم در مزارع ديم بروجرد

Investigating Seasonal Population Dynamics, Sampling Methods and Sample Universe of the Important Wheat Aphids Wheat Rain Fed Fields in Boroujerd

Sitobion avenae (Rodani). Schizaphis grammnm (Fabtic iusl and Diuraphis noxia (Mordviko ) arc the most important aphids in wheat rain fed fields of Broujerd. In this research, seasonal population dynamics and selection of sampling methods as well as sample universe of these species were investigated during ~003-2005. Sampling was done twice a week and during three months loy using X, lJ and zig-zag shaped movement in the lieIds. In each occasion, 100 plants were selected randomly in each field and adults as well as nymphs of each species were recorded. Result showed that there were tVIO population peaks ofS avenue and one lor S. grcnniniun and D. noxia. S XIʹ(//I/il/I/III which appeared 5-7 day s earlier than the two species in the agronomic conditions. Relative variat ion (RV) and rc Iʹll ivc net precision (RNP) vI ere compared to dctcrm inc the best sampling methods. Comparison of three methods of sampling indicate that X- shaped movement was more precise that U and zig-zag shaped methods of movement. Results of regression stablishmcnt between the number of aphids on target organs and the whole number of aphids per occasion showed that in pre heading periods for Smʹcllo(ʹ the leaves hUI for S.xrolllilll/III and lr.uoxia the flag leaves were suitable sample universe. In post wheat, car was an appropriate place to take samples from the plant.