الفهرس 
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Abstract
Canola, Brassica napus L. is one of the most important oil crops and at present, is the third largest source of vegetable oil all over the world. In Egypt, canola has a bright future to contribute in reducing oil deficiency gap between production and consumption of edible oil; particularly it could be successfully grown during winter season in newly reclaimed land outside the old one of Nile valley to get around the competition with other crops occupied the old cultivated area. The present studies were undertaken for two canola growing seasons (2013-2014 and 2014-2015).
Results were reported in accordance with the objectives outlined above as follows:
1. Population density and fluctuation of common sucking insect pests on canola plants
1.1. Cabbage aphid, B. brassicae
1.1.1. Population density and fluctuation of cabbage aphid
The population of cabbage aphid, B. brassicae started its appearance in canola plants between mid and last November and disappeared completely from canola plants during the 2nd week of April during both seasons of this study. During this period of appearance, the pest population increased gradually till reached its peak of 143.67, 148.33 and 151.67 aphids/plant (Max. temp. 25.2°C, Min temp. 7.6 °C and RH 60%) and 122.33, 122.67 and 122 aphids/plant (Max. temp. 18.6°C, Min temp. 5.6 °C and RH 70%) on Serw 4, Serw 6 and Pactol varieties respectively during the 3rd and 4th week of February of 2013-2014 and 2014-2015 seasons.
1.1.2. Effect of some weather factors on cabbage aphid population
Cabbage aphid population was highly significant and negatively correlated with maximum temperature (-0.300, -0.302 and -0.309), minimum temperature (-0.294, -0.305 and -0.283) and relative humidity (-0.193, -0.250 and-0.208) for (Serw 4, Serw 6 and Pactol varieties) during 2013-2014 season. Whereas, it was significant and negatively correlated with maximum temperature (-0.143, -0.103 and -0.120), minimum temperature (-0.178, -0.132 and -0.176) and non significant positively correlated with relative humidity (0.017, 0.103, 0.010) for (Serw 4, Serw 6 and Pactol varieties) during 2014-2015 season.
1.1.3. Impact of selected insecticides on the population of cabbage aphid
Foliar application of selected insecticides on the cabbage aphid under field conditions showed that all treatments caused significant reductions to aphid population at 1, 3, 7, 15 and 21 DAT compared to the control on canola plant (Pactol variety) during 2014-2015 season. Thiamethoxam, diazinon and carbosulfan gave a high efficiency reduction against cabbage aphid compared to acetamiprid, dinotefuran and imidacloprid. Thiamethoxam induced a maximum reduction in aphid population, 62.07, 89.80, 96.02, 96.59 and 94.55% at 1, 3, 7, 15 and 21 DAT respectively with an average 87.81%. Diazinon caused 38.60, 87.87, 94.83, 92.00 and 75.40% with an average 77.74%; carbosulfan caused 37.90, 85.77, 89.80, 93.30 and 60.50% with an average 73.45%; acetamiprid and dinotefuran had a similar effect with an average reduction of 65.22 to 65.97%. In contrast imidacloprid showed the lowest reduction which caused 9.90, 60.70, 78.53, 78.70 and 41.93% at different dates respectively with an average 53.96%. The reduction percent of population increased over the time maybe that the cabbage aphid was more tolerant to these insecticides or because the residual activity of these insecticides decreased due to environmental factors over time.
1.1.4. Toxicity of some insecticides to the cabbage aphid
Comparison between the LC50s of the tested neonicotinoid (Ne), carbamate (Cb), organophosphate (Op) and pyrethroid (Py) insecticides for the adults of the cabbage aphid, B. brassicae, under laboratory conditions after 24 and 48 hrs of exposure showed that the most toxic insecticide by ppm (unit weight of active ingredient) was pirimicarb (3.79, 0.15), followed by diazinon (13.88 and 2.06), acetamiprid (79.7 and 3.57), methomyl (71.8 and 6.04), malathion (48.15 and 28.21), lampada-cyhalothrin (28.28 and 11.84), thiamethoxam (96.8 and3.14), carbosulfan (199.75 and 11.70), imidacloprid (297 and 159) and dinotefuran (321 and 72.77). The LC50s for pirimicarb and diazinon are not significantly different after 24 hrs (95% FL overlap), while the LC50s for these insecticides are significantly different from other insecticides.
Based on the relative potency, pirimicarb (Cb) was more effective than methomyl and carbosulfan by (18.94 and 40.27) and (52.70 and78) fold after 24 and 48 hrs. Also, pirimicarb (Cb) was more effective than Ne, thiamethoxam, acetamiprid, dinotefuran and imidacloprid by (25.54 and 20.93), (21.10 and 23.80), (84.70 and 485.13) and (78.36 and 1060) fold. Pirimicarb (Cb) was more effective than Op, diazinon and malathion by (3.66 and 13.73) and (12.70 and 188.10) fold. Pirimicarb (Cb) was more effective than Py, lampada-cyhalothrin by (7.46 and 78.93) fold after 24 and 48 hrs of exposure. These results indicated that pirimicarb (Cb), thiamethoxam (Ne) and diazinon (Op) were the most toxic insecticides against cabbage aphid, followed by others insecticides.
1.2. Green beach aphid, M. persicae
1.2.1. Population density and fluctuation of green beach aphid
In 2013-2014 season, the highest numbers of aphids were 15.7, 9.0 and 7.3 aphids/10 plants recorded during the 1st week of March, the last week of January and the 2nd week of February on Serw 6, Serw4 and Pactol varieties respectively. In 2014-2015 season, these numbers were 13.7, 12.0 and 11.3 aphids/10 plants on the same varieties during the 3rd week of January (Max. temp. 27.8°C, Min temp. 6.8 °C and RH 52.5%), the 1st week of February (Max. temp. 26.0°C, Min temp. 6.4 °C and RH 52.5%) and the 2nd week of February (Max. temp. 22.8°C, Min temp. 9.0 °C and RH 52.5%), respectively.
1.2.2. Effect of some weather factors on green beach aphid population
Green beach aphid population was highly significant and negatively correlated with maximum temperature (-0.292, -0.297 and -0.272), minimum temperature (-0.340, -0.271, -0.486) and relative humidity (-0.336, -0.393 and -0.323) for (Serw 4, Serw 6 and Pactol varieties) during 2013-2014 season. Whereas, it was significant and negatively correlated with maximum temperature (-0.233, -0.289 and -0.426), minimum temperature (-0.342, -0.364 and -0.423) and non significant negatively correlated with relative humidity (-0.097, -0.079, -0.049) for (Serw 4, Serw 6, Pactol varieties) during 2014-2015 season.
1.3. Thrips, T. tabaci
1.3.1. Population density and fluctuation of thrips
The appearance period of thrips, T. tabaci (nymph and adult stages) on canola plants was approximately during November to March of 2013-2014 and 2014-2015 seasons. During 2013-2014 season, the maximum population of the thrips was recorded as 27.27, 30.90 and 27.47 insect/plant in last half of December on Serw 4, Serw 6 and Pactol varieties respectively. In 2014-2015 season, the maximum population of thrips found as 22.33, 25.33 and 28 insect/plant and observed between the last week of December and the first half of January on Serw 4, Serw 6 and Pactol varieties, respectively.
1.3.2. Effects of some weather factors on thrips population
The thrips population showed highly significant negative correlation with Max temp. (-0.815, -0.789 and -0.746) and Min temp.( -0.711, -0.748 and -0.656), whereas, it was non- significant and positively correlated with relative humidity (0.021, 0.061 and 0.027) for Serw 4, Serw 6 and Pactol varieties respectively during 2013-2014 season. In 2014-2015 season, the trend was similar to first season, the population of this pest showed highly significant negative correlation with Max temp. (-0.639, -0.688 and -0.721) and Min temp.( -0.686, -0.777 and -0.754), whereas, it was non- significant and positively correlated with relative humidity (0.083, 0.024 and 0.082) for Serw 4, Serw 6 and Pactol varieties, respectively.