الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Agriculture depends to a large extent on the use of pesticides, especially those belonging to the group of neonicotinoid pesticides. Since this group entered the global pesticide market at the beginning of the nineties of the last century, their production and spread have increased to currently represent approximately 26% of the total sales of pesticides in the world and have been registered in more than 120 countries. Neonicotinoids are systemic pesticides and are extremely effective in the control of piercing-sucking insects as the absorbing perforator acts as a neurotoxin. Therefore, it was necessary to find chemical compounds that are highly effective in the control of piercing-sucking insects and can be used as alternatives to neonicotinoids. For this purpose, this study was conducted to evaluate the effectiveness of some different chemical pesticides and some natural compounds on whiteflies and aphids under laboratory and field conditions.
1. Laboratory experiments
1.1 . Bio-evaluation studies on honey bees:
The results of the biological evaluation of the tested compounds on honeybee workers were recorded 4 hours after treatment, and a change occurred in the LC50 values due to the difference in the degree of toxicity of each compound to honeybees. Five concentrations of the following chemical and natural compounds were used in the biological evaluation:
• 0.6,0.4,0.3,0.2 and 0.1 ml/L of thiamethoxam
• 1,2,4,8,6 and 10 ml/L of sulfoxaflor
• 0.125,0.25, 0.5, 1, 5, and 10 ml/L of super-Rego
To study their toxicity on honey bees, the death rate was estimated after 4, 24, 48, and 72 hours of treatment. It was found that some of the pesticides used had no effect on honey bees, while others increased their death rate with increasing concentration. The most toxic compounds on honey bees was thiamethoxam then super-Rego and finally sulfoxaflor as the least toxic.
1.2. Bio evaluation studies on whitefly Nymphs (Bemisia tabaci) and aphids (Aphis craccivora)
The results of the biological evaluation of the tested compounds were recorded on the second and third instars of whitefly nymphs and aphids after 24 hours of treatment. There was a change in the LC50 values due to the difference in the degree of efficiency of each compound for whitefly nymphs and aphids. Five concentrations of the following chemical and natural compounds were used in the biological evaluation:
• 0.06, 0.03, 0.01 and 0.125m/L of thiamethoxam, sulfoxaflor
• 50,40,30,20 and10 ml/L of spirotetramat
• 5,4,3,2,1,0.5,0.25and 0.125 ml/L flonicamid
• 7,6,5,4,3,2,1,0.5 and0.25 ml/L of pymetrozine
• 50,25,10,5,1,0.5ml/L of super-Rego pesticide, bernaStar, topNine
To study its effectiveness on whitefly nymphs and aphids, the death rate was estimated after 24 hours of treatment. It was found that the death rate increases with increasing concentration and the effectiveness on aphids was in the following descending order:
thiamethoxam> sulfoxaflor> pymetrozine> flonicamid> super-Rego > topNine > bernaStar > spirotetramat
The order of the compounds effect on the second and third instar nymphs of the whitefly was in descending order in terms of effectiveness as follows:
thiamethoxam> sulfoxaflor> flonicamid> pymetrozine> super-Rego> topNine> spirotetramat > bernaStar
2. Field experiments
A comparison was conducted between nine treatments, five different chemical pesticides (thiamethoxam, sulfoxaflor, spirotetramat, flonicamid, pymetrozine) and three natural pesticides (super-Rego, topNine, bernaStar) in addition to the control (spraying with water without adding a compound) at the recommended concentrations (60 g/L, 50 cm3/fadan, 75 cm3/100L, 20,50g/100L, respectively). Three sprayings were carried out, 10 days apart from each spraying, based on the percentage of reduction in the number of incomplete stages of whiteflies and aphids on green bean plants and tomato plants. The study was carried out during two different years in Giza Governorate at a research station - Faculty of Agriculture - Cairo University. Experiments were conducted within a month August 2020, 2021.
• It was found that the percentage of reduction in the number of whitefly nymphs on green bean plants increased with an increase in the number of spraying times in both successive seasons. thiamethoxam recorded the highest percentage of reduction (72.2 and 79.2) respectively, followed by sulfoxaflor (74.1 and 74.2), respectively, while the lowest reduction percentage was recorded by berna-Star (32.2 and 33.5), respectively.
• It was found that the percentage of reduction in the number of aphids on green bean plants increased with an increase in the number of spraying times in both successive seasons. thiamethoxam recorded the highest percentage of reduction (85.6 and 84.4) respectively, followed by sulfoxaflor (78.2 and 74.9) respectively, while the lowest percentage reduction was recorded by bernaStar (33.5 and 34.5), respectively.
• It was found that the percentage of reduction in the number of whitefly nymphs on tomato plants increased with an increase in the number of spraying times in both successive seasons. thiamethoxam recorded the highest percentage of reduction (79.1 and 89) respectively, followed by sulfoxaflor (89.4 and 84.4) respectively, while it recorded the lowest percentage. berna-Star reduction ratio (36.5 and 49.2) respectively.
• It was found that the percentage of reduction in the number of aphids on tomato plants increased with an increase in the number of spraying times in both successive seasons. thiamethoxam recorded the highest percentage of reduction (99.4 and 100) respectively, followed by sulfoxaflor (85.5 and 90.4) respectively. The lowest reduction percentage is berna-Star (52.8 and 51.1), respectively.
3. Analysis of pesticide residues in green beans and tomatoes
• The highest rate of decomposition of pesticide residues in green bean fruits was thiamethoxam, spirotetramat, and flonicamid.
• The highest decomposition rate of pesticide residues in tomato fruits is pymetrozine, while the lowest decomposition rate is flonicamid.
• The fastest decomposition of pesticide residues occurred in green beans.