الفهرس 
Introduction
Effect of some natural factors on the populationsOnly 14 pages are availabe for public view
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Abstract
Recently, sugar beet; Beta vulgaris L. takes its second periority in sugar production, in Egypt. Thus, sugar beet is grown in wide area in Egypt, specially at Kafr ElSheikh Governorate. Its area greatly increased year after year. Many series insect pests were attacking the sugar beet plants during the growing season. Complete knowledges of main insects and the economic importance of each one was considered and the safe control methods were applied Thus, the present study was carried out at SediSalem district, Kafr ElSheikh Governorate during three seasons from 2001/2002 to 2003/2004). The main insects were studied in this investigation includes: a. Piercing sucking insects: Bemisia tabaci (Geen) adults., Aphids; nemphs and adult, Empoasca decipiens (Paoli) adults and Nezara viridula; nemphs and adult. b. Leaf miners insects: Pegomyia mixta (Vill.) egg and larvae, Lixus junci (Boh) larvae and Scrobipalpa ocellatella (Boyd) larvae. c. Chewing insects: Cassida vittata (Vill.) larvae and adult, Spodoptera littoralis (Boisd) larvae and Spodoptera exigua (Hb.); larvae. d. Natural enemies predators: Cocceniella undecimpunctata larvae and adult, Chrysoperla carnea (Steph.) eggs and adult, Scymnus syriacus, adult, Peaderius alfierii Koch; adult and true spider; adult, were the most serious and abundant on sugar beet plants. Therefore, their population densities on four planting dates (mid. Aug., mid. Sept., mid. Oct. and mid. Nov.) were studied during two successive seasons; (2001/2002) and (2002/2003). Population densities of main insects on sugar beet plants in four planting dates: a. Piercing sucking insects: 1. Cotton whitefly B. tabaci: The present infestation by the sucking insects specially B. tabaci appeared in highest population during Aug. plantation, while the lowest one in Sept. planting date and B. tabaci numbers were absent during Oct. and Nov. plantation. Correlation between B. tabaci population and meteorological factors gave significant and positive with max. & min. temp. and min. R.H, while gave nonsignificant and positive with max. RH. Relative humidity had a slight effect on B. tabaci population than temperature. 2. Aphis gossypii: Sugar beet plants harboured highest population aphid during Oct. plantation, while the lowest one was during Nov. plantation and aphid number were absent during Aug. and Sept. Correlation between aphid number and meteorological factor gave significant positive with max. & min. temp., while gave nonsignificant negative with max. & min. R.H. Relative humidity (R.H) had a slight effect on aphids population than temperature. 3. Leaf hopper Empoasca decipience: The highest number of E. decipiens appeared during Sept. and Nov. plantation, while the lowest ones recorded during Oct. or Aug. Correlation between jassids population and meteorological factors gave positive significant with max. & min. temp., while gave non negative significant with max. & min. R.H. Temperature had a high effect on Jassids population than R.H. 4. Green stink bug (Nizara viridula): The number of green stink bug recorded highest population during Nov. plantation, while gave lowest number during Aug. plantation and absent during Sept. plantation.