الفهرس 
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Abstract
Canola plant (oilseed rape) Brassica napus L. belongs to the Brassicaciae family (formerly Cruciferae). Nowadays it becomes one of the important oil crops all over the world. It has the second position in the total world area for oil crops, the third in the world oil production and the fifth in the world international trade for crops. In Egypt, canola cultivation is recommended for increasing the total oil production to bridge the gap between production and consumption of the edible oil, which did not cover the total needs of local consumption.The present studies were carried out throughout the period from 2008-2009 to 2009-2010;field and laboratory studies were conducted. The main objectives were to survey of pests inhabiting canola plants and their natural enemies at Assiut, studying the seasonal abundance of the aphid species infesting canola, biological and morphological studies of the major aphid species infesting canola (cabbage aphid).
The obtained results could be summarizing as follows:
A) Ecological studies:
-Survey of pests and their natural enemies (predators, parasitoids and pathogens) inhabiting on canola plants at Assiut
A partial taxonomic list of pests and their natural enemies (predators, parasitoids and entomopathogenic fungi) recovered by sweep net and direct count from canola plants at Assiut indicate the presence of 24 species of arthropods belonged to 19 families and 14 orders. from the arthropods species collected, 5 species are considered main pest causing great damage, 7 slightly harmful, 2 visitors and 10 beneficial arthropods as well as two species of entomopathogenic fungi were recovered.
The most important serious pests were the complex of aphid species i.e. Brevicoryne brassicae L., Myzus persicae (Sulz.) and Lypaphis erysimi (kalrenbach).
The green lacwing, Chrysoperla carnea (Steph.), the hover fly, Syrphus corolla and the lady beetles, Coccinella undecimpunctata L., were the most abundant predators, which recorded and identified.
There are two species of primary parasitoid were recorded and identified attacking aphid species infesting canola belonging to order Hymenoptera Family Aphidiidae namely: Diaeretiella rapae (Mclntoch) and Praon necans Mackauer.
Field survey of entomopathogenic fungi infecting cabbage aphids infesting canola plants generated data on two species of fungal pathogens, including one Entomophthorales and one Hyphomycetes.
-Dominance and abundance degrees of aphid species infesting canola plants:
Data show that B. brassicae seems to be the most important economic pests infesting canola as indicated by the highest value of dominance and abundance degrees (81.82 and 100%)Cabbage aphid, B. brassicae
The migration of aphid from the overwintering site into canola field occurred after about 23 days (nearly during the third week of December). The population then increased to become 10% of the maximum number after 49 days (nearly during the third week of January). Maximum population density of the cabbage aphid occurred after about 97 days.Therefore, the peak of abundance could expect around the end of February and the beginning of March. After the population reached its highest level it generally declined and reached 10% of the maximum after 112 days. The population then vanished from the canola field in 122 days (toward the end of March).
Green peach aphid, M. persicae
The green peach aphid began to appear on canola plants on 3rd week of December with few numbers when the plants were in the seedling stage. Afterwards, the population of aphids increased gradually to reach a peak of abundance during the first week of February. Then the number of aphids began to decline until the first week of March, when the aphid disappeared from the plants.
Turnip aphid, L. erysimi
The population of the turnip aphid began to appear on the canola plants approximately during the third week of December and developed on the plants up to the first half of February and varied from one year to another. Its maximum population densities were recorded during the end January and the beginning of February.
B) Biological studies
The present results show the effect of constant temperatures 20,24 and 28 C on the developmental periods and survival of different nymphal instars as well as the reproductive potential of the adult stage.
Nymphal stage
The durations of nymphal instars and the percentage of survival decreased significantly with the increase in temperatures.
The calculated developmental threshold of the whole nymphal stage was estimated as 7.17C.The thermal units needed for the development of the whole nymphal stage of the cabbage aphid were 97.78 day-degrees.
Use of effective temperature in determining of generation of B. brassicae on canola
The calculated average generation numbers of the pest were about 63.28 generations of the pest could develop in one year under Assiut conditions, out of which about 12 generations could develop during the canola growing season.
Adult stage
The results indicate that reproductive periods decrease with increase in temperature. The mean reproductive period ranged from 8.27 days at 20 to 5.53 days at 28ºC.The mean number of nymphs per aptera increased as temperature increased up to 24ºC, where the maximum number of nymphs (22.93 nymphs) was produced In general, it could be concluded that a constant temperature of 24 ºC was nearly the optimum, followed by temperature of 20ºC.According to the calculated life table parameters which have been taken into consideration of the cabbage aphid were: Generation time (GT), (Population doubling time (DT), Net reproductive rate (R ) and the intrinsic (rm) and finite rates of increase (λ).
The duration of one generation of B. brassicae lasted about 12,11 and 9 days at 20.24 and 28ºC, respectively.
The population of this pest had the capacity to double every 2.66,2.79 and 2.14 days at 20.24 and 28ºC, respectively.The values of rm at 20º and/or 24º (02603 and 0.2488)were approximately about four times higher than those of the pest at 28ºC(0.0599).On the other hand, when the values of rm were converted to the finite rate of increase (λ), it clear that the population of B. brassicae had a capacity to multiply about 1.2973, 1.2825 and 1.0617 times per aptera per day at 20,24 and 28ºC, respectively.
from the above-mentioned results it could be concluded that temperatures of 20 and 24ºC were most favourable for multiplication of the pest.
C) Morphological studies
This part of study focused on the ultra structure of the sensilla on different parts of cabbage aphid, Brevicoryne brassicae,body and the differences between alate and aptera using scanning electron microscope.
General morphology
Cabbage aphid’s body is covered dorsally and ventrally with white powdery waxy exudates. It is divided into head, thorax and abdomen. In alate forms, the head and thorax are strongly sclerotized and sharply distinguished from each other and the abdomen is membranous. On the other hand, head of apterae is fused with the prothorax.
In alate, the frons is W-shaped due to presence of median tubercle while in apterae, is slightly convex.
The compound eyes are large in alate than in the apterae. The diameter of the lens is greater in alate than in apterae. Alate forms also differ from apterous in having three ocelli.
Ultra structural results
Antennal sensilla:
Apterae have antennal sensilla similar to those of the alate. Generally, antennae covered with trichoid sensilla (typeΙ). A group of four basiconic sensilla occur at the tip of the antennae. In alate forms, single finger-like basiconic sensilla found on the unguis while in apterous forms the unguis bears single trichoid sensilla. A flattened sense organ called primary rhinarium occurs on the 5th antennal segment. It is a pair of campaniform sensilla . Another one plus pair of small placoid sensilla and single rosette- like coeloconic sensilla occurs on the end of the basal part of the 6th antennal segment. They are ringed with a fringe of cuticle of which a finger-
like extension protrudes which function as a protective sieve against the entry of undesirable particles.
Alate forms differ from apterae by the possession of many secondary rhinaria on the third antennal segment. Secondary rhinaria are placoid sensilla. In both forms single campaniform sensilla and single coeloconic sensilla is present on the pedicel.
Sensilla on mouthparts:
The labrum covered with trichod sensilla both type (Ι) and type (Π). The 2nd and 3rd segments of rostrum bearing trichoid sensilla type (Ι). The rostral segment has both trichoid sensilla type (Ι) and (Π). The short hairs or pegs on the tip of rostrum are simple mechanoreceptor.
Sensilla on legs:
Leg is covered with many trichoid sensilla type (Ι). The 1st tarsal segment bears only three trichoid sensilla type (Ι) ventrally.
Sensilla on wings:
The wings possess mechanoreceptive sensilla to monitor wing movements. These sensilla are mainly trichoid blunt sensilla. They are big, rabbit ear-like trichoid blunt on veins and wing edges and small on the rest of the wing.
Cauda:
The cauda bears three types of sensilla. It is mainly covered with dense basiconic sensilla and some trichoid sensilla of both types (Ι) and (Π).