الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 227 |  |  |
| | | from | 227 | | |
Abstract
The study was conducted in the gardens of Baghdad university in Iraq which located in AL-Jadria compass. This was in the period of time from February 2023 to June 2023. Temperature and humidity data were sourced from an Iraq Agrometeorological station.The insect species used in this work was Aphis nerii which parasitize three plant host species, namely, Nerium oleander, Pilea serpyllacea and Cascabela thevetia to study suscebtibility and the population dynamics of the insect on the three plant speciesSamples of the examined insect were collected weekly as regular intervals where each sample invalves 3 inlested leaves from different places of the plant hostes from the bottom, middle and top sections of the plants. However, the number of nymphs and adults was counted in the laboratory.The present work used the extracts of two plants species and treated the insect with them to know their effects and using them as sustainable pests management strategy. These extract were lemongrass extract and lavender extract. The lemongrass extract was prepeared from the leaves of the plant grown in the gardens of Baghdad university, where that of lavender was preoared from 200g from the flower buds of the plant taken from medicinal herbs store.Tow experiments were carried out, one of them in the laboratory and the other in the field where the plant hosts were found. Also, two plants extracts were used in the experiments with different concentrations and various exposure times. These concentrations were 5000,10.000 and 20.000 ppm for each extract, where the exposure times were 6h, 12h and 24h.from the two experiments the results were as the following -It was noticed that aphid population was peaked in Aphid and declined in both May and June and the temperature played a mains rde in influencing population growth of the aphis on its plant hosts. Moreover, it was noticed that the plant Nerium oleander was the preferred host supporting the highest aphid denisties, Cascabela thevetia supported moderate aphid densities Pilea serpyllacea supported very low aphid densities.With respect to the two plant extract it was noticed that the lemongrass extract showed strong, concentration-dependent insecticidal or repellent effect against aphids. It was more dangerous on the insects infested Pilea serpyllacea, immediate efficacy on the insects infested Cascabela thevetia and less effective on the insects infested Nerium oleander. Meanwhile, examination of lavender extract revealed that it had the stronder effect on the insects infested Cascabela thevetia compared to lemongrass extract, with similar effect to that of lemongrass on the insects infested Pilea serpyllacea and with the leser effect on the insects infested Nerium oleander as in lemongrass extract. from the above results it can be recorded that the active component of each extract might explain their varying efficacy on the examined insects. Also,the plant chemistry might influence the effectiveness of the extracts or aphid resistasnce. Moreover, Aphis nerii which infest the plant host Nerium oleander might have developed resistence to lavender extract. Finally, the environmental conditions might effect the extract’s activity.Moreover, the above results in the present study revealed that lemongrass extract presents a promising host – specific tool for controlling Aphis nerii, particularly on the plant hosts Pilea serpyllacea and Cascabela thevetia. Adding to these results the botanical extract effeciacy can vary depending on the host plant and the environmental conditions. This recommend that further researches in needed to optimize the use of botanical extracts for aphid control and understand the mechanisms of resistasnce development. The present study also provides valuable insights into the complex relationship between Oleander aphids and their plant hosts and demonstrates the potential of botanical extracts as a sustainable pest management strategy. Moreover, this work revealed detailed data on the effect of both extracts on the different plant hosts ana exposure times. Statistical analysis was conducted to support the observed trends.from other point of view the two plant extracts were analysed with gas chromatography / mass spectroscopy to know the chemical structure and the principle oils of both of them. Both lemon and lavender essential oils contain a complex mixture of volatitle compounds, with monoterpenes and sesquiterpenes being the major constituents. With respect to the lemon extract, the major monoterpenes are limonene (66.82 %) B – pinene (1.68 %) and linalool (7.42 %), where the major sesquiterpene was representealy ley caryophyllene oxide (2.98 %). Meanwhile, for the lavender extract, the analysis revealed that major monoterpenes were composed of cinede (20.02 %), linalool (15.06 %) and x –terpinel (7.52 %), while the major sesquiterpenes were composed of caryophyllene oxide (2.90 %) and x – santalene (0.39 %). Moreover, the present study investigated the histolgical structure of the examined insect Aphis nerii through paraffin wax sections in the Oleander aphid in both the control and treated groups. These sections were examined using the light microscope and photographed to be recorded in this thesis and to know the toxic effect of the two plant extracts and the changes occurred in the examined insect to its internal organs. The altrations in the insect were tearing and rupture of the exoskeleton, degeneration of the salivary glands, midgut and muscles and increased fat bodies storage. All of these changes leads to the loss of the aphid’s ability to feed, digestion and move. Also, the accumulation of the fat bodies was attempt to store energy. These effects were increased with the increas of concentrations of the extracts and increasing of exposure times.Finally, the present work recommended thet further research is needed to optimize the concentration, application method and potential synergistic effect of these substances for effective and environmentally friendly control.