The insecticidal activities of essential oils obtained from black pepper, eucalyptus, rosemary, and tea tree and their binary combinations were investigated against the green peach aphid, Myzus persicae (Aphididae: Hemiptera), under laboratory and glasshouse conditions. All the tested essential oils significantly reduced and controlled the green peach aphid population and caused higher mortality. In this study, black pepper and tea tree pure essential oils were found to be an effective insecticide, with 80% mortality when used through contact application. However, for combinations of essential oils from black pepper + tea tree (BT) and rosemary + tea tree (RT) tested as contact treatment, the mortality was 98.33%. The essential oil combinations exhibited synergistic and additive interactions for insecticidal activities. The combination of black pepper + tea tree, eucalyptus + tea tree (ET), and tea tree + rosemary showed enhanced activity, with synergy rates of 3.24, 2.65, and 2.74, respectively. Essential oils formulation was effective on the mortality of aphids. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that stability of a mixture of essential oils was not affected by store temperature (15, 25, and 35 °C) and the functional groups were not changed during storage. Based on our results, the essential oils can be used as a commercial insecticide against M. persicae.

Headspace solid microextraction (HS-SPME) and GC-MS were used to investigate volatile organic compounds (VOCs) from cabbage plants infested and uninfested with green peach aphid Myzus persicae. The HS-SPME combined with GC-MS analysis of the volatiles described the differences between the infested and uninfested cabbage. Overall, 28 compounds were detected in infested and uninfested cabbage. Some VOCs released from infested cabbage were greater than uninfested plants and increased the quantity of the composition from infested plants. According to the peak area from the GC-MS analysis, the VOCs from infested cabbage consisted of propane, 2-methoxy, alpha- and beta pinene, myrcene, 1-hexanone, 5-methyl-1-phenyl-, limonene, decane, gamma-terpinen and heptane, 2,4,4-trimethyl. All these volatiles were higher in the infested cabbage compared with their peak area in the uninfested cabbage. The results of the study using a Y-shape olfactometer revealed that the VOCs produced by infested cabbage attracted Myzus persicae substantially more than uninfested plants or clean air. The percentage of aphid choice was 80% in favor of infested cabbage; 7% were attracted to the clean air choice and uninfested plants. A total of aphids 7% were attracted to clean air. Comparing between infested and uninfested cabbage plants, the aphid was attracted to 63% of the infested cabbage, versus 57% of the uninfested cabbage. The preferences of Aphidus colemani and Aphelinus abdominalis to the infested or uninfested plants with M. persicae and compared with clean air indicated that parasitoids could discriminate the infested cabbage. Both parasitoids significantly responded to the plant odor and were attracted to 86.6% of the infested cabbage plants.

Volatile organic compounds (VOCs) from uninfested and infested broccoli plant samples with green peach aphid Myzus persicae were investigated by headspace solid microextraction (HS-SPME) combined with gas chromatography mass spectrometry (GC-MS). Overall, 25 compounds were identified in uninfested and infested broccoli plants. The HS-SPME combined with GC-MS analysis of the volatiles described the differences between the infested and uninfested broccoli plant samples. Based on peak area from the GC-MS analysis, the VOCs from infested broccoli were significantly greater than that from uninfested broccoli, such as D-limonene, Undecane, 3,4-dimethyl-, Heptane, alpha-Pinene, Oxalic acid, Citronellol, Tridecane, n-Decanoic acid, Cyclopentane, pentyl- and n-Hexadecanoic acid compared with volatiles released from uninfested broccoli. The results of Y-tube olfactometer showed that Myzus persicae were significantly attracted by the VOCs released from infested broccoli plants, more than uninfested plants or clean air. The percentage of aphid choice was 70% towards infested broccoli, and 10% were attracted to the clean air choice and uninfested plants. With the comparison between clean air and uninfested plants, the aphids were attracted by 84% for broccoli, while 7% were attracted towards clean air. Comparing between infested and uninfested, the aphid attracted by 26.6% for infested broccoli, versus 30% for uninfested broccoli. The preferences of Aphidus colemani to the infested, uninfested plants with M. persicae and compared with clean air were measured. The results indicated that parasitoids could discriminate the infested broccoli and significantly respond to the plant odour and attractive by 100% for the parasitoid towards infested broccoli plants.

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The sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is one of the most important pests in vegetables. Although the host plant Solanum melongena, is considered the most preferred, the whiteflies have preferences for particular varieties of eggplant. In this study, we evaluated three eggplant varieties in choice feeding tests. We found that the varieties of Zomorrod and Barcelona were the most preferred with the highest numbers of whitefly nymphs, which were 312 and 300 per leaf, respectively, on the last week of May. In comparison, the nymph average was 171.8 per leaf on the last week of May on the kareema. Chlorophyll concentration has been negatively affected by the infestation of B. tabaci. The investigation of the chlorophyll content ratio between the uninfested and infested eggplant leaves showed a decrease in chlorophyll content at 13.95 and 6.60 11 mg/L of the Zumorrod variety for the uninfested and infested leaves, respectively, with 52.67% chlorophyll reduction. At the same time, the mean chlorophyll content for uninfested and infested eggplant leaves of the Barcelona variety was 12.74 and 4.95 mg/L, respectively, with 61.14% chlorophyll reduction. At the same time, the Kareema variety was recorded at 17.49 and 4.95 mg/L for the uninfested and infested leaves, respectively, with 72.39% chlorophyll reduction. Furthermore, feeding by B. tabaci reduced leaf photosynthesis in eggplant by restricting gas exchange through stomata and reducing chlorophyll's content and photosynthetic capacity. Keywords: population density; piercing pest; Bemisia tabaci; Solanum melongena; host preference; plant pigments