الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Summary
Sugarbeet (Beta vulgaris L .) is the 2nd crop for sugar production in the world (28%) and in Egypt (25%) . The tortoise beetle , Cassida vittata Vill. ( Coleoptera: Chrysomelidae) is one of the most serious and destructive pest of sugarbeet in Egypt . Larvae and adults feed on leaves , resulting reduction in the size of roots and , subsequently , losse in sugar productoin . The presented study aimed to find out some biocontrolling methodes of this pest , results may be summarized as follows : 1- Field experiments. 1.1.Assessment of susceptibility of sugarbeet varieties toinfestation with the tortoise beetle , Cassida vittata
Vill. 1.1.1. Population densities of C. vittata
The infestation with C. vittata on monogerm was lower than polygerm varieties. Kawemira ( as polygerm) had the highest root yield and the least infestation with C. vittata . Also , Marathon ( as monogerm ) had the highest root , leaves and biological yields and the least infestation with C. vittata . 1.2 . Population density of sugarbeet tortoise beetles C. vittata stages and their associated natural enemies. 1.2.1. Population fluctuation of tortoise beetle, C. vittata
Population density of adults in the 2nd planting date (20.82 adults /5 plants) ) was significantly lower than 1st one
(22.85 adults /5 plants) and vice versa for pupal stage. However, there were no significant differences between the tested planting dates for eggs and larval infestation. Generally the first infestation with adults, eggs, larvae and pupae were recorded in mid-January, mid-January, mid-February and mid-March,
respectively.
1.2.2. Predatory insects :
Seven predaceous insect species were found associated with sugarbeet plants in western Nubaryia. Those were Coccinella septempunctata, Coccinella undecimpunctata, Cydonia vicina var .nilotica , Cydonia vicina var. isis , Paederus alferii (Coleoptera), Chrysoperla carnea (Neuroptera)and Syrphus corollae (Diptera ) .
Population of C. vicina var. nilotica , C. vicina var. isis and S. corollae were higher in the 2nd planting date than the 1” one . However, there was no significant differences between the two tested planting dates for C. septempunctata, C. undecimpunctata , P. alferii and Ch. carnea . The surveyed predators could be arranged in a descending order occording to their population densities as ; C. vicina var. isis > C. vicina var .nilotica > C. undecimpunctata > P. alferii > C. septempunctata > C. carnea > S. corollae ( 14.81, 13.15 , 12.89, 12.36 , 10.17, 9 and 6.81 individual / 50 double strokes, respectively .
The earliest appearance of the tested predators occurred in mid-December for C. vicina var. isis, C. vicina var .nilotica and P. alferii, 1st January and mid-February for C. septempunctata
and S. corolla, respectively, and 1St February for C. undecimpunctata and C. carnea .
Population densities of C. undecimpunctata , C. vicina var .nilotica and S. corollae, increased gradually till the harvest (the lst-June). However, (C.septempunctata , C. vicina var. Isis and Ch . cornea ) populations increased till the mid-April then decreased till the lst-June . P. alferii increased in number till mid-May then decreased .
1.2.3. Parasitic insects :
Two hymenopterous parasitic species were obtained from C . vittata stages : Monothocheata nigra Blood and Kryger Family (Trichogrammatidae) from eggs, and the gregarious pupal endoparasitoid , Tetrastichus sp. Eulophidae from pupae .
1.2.3.1. Monothocheata nigra .
Thje parasitism by M nigra on C. vittata eggs started at the beginning of February. The maxima percentages of parasitism , in 1997/98 season reached 17.54% on mid-April for the first planting date and 12.42%on April , 1st for the seconed one in the subsequnt season , these peaks reached 9.96% and 9.29% on mid-Mach and April 1st in the two planting dates, respectively . After the peak of parasitusm, the perecentage declined until disapeared by the beginning of June .