Effect of nitrogen fertilizer on some tritrophic interactions among cucumber plant, the melon aphid, Aphis gossypii and the predatory midge, Aphidoletes aphidimyza

Honarvar Namin, Parvin (2019) Effect of nitrogen fertilizer on some tritrophic interactions among cucumber plant, the melon aphid, Aphis gossypii and the predatory midge, Aphidoletes aphidimyza. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

Research aim: In this study, the effect of fertilization of cucumber plants with different levels of nitrogen was investigated on the demography and functional response of Aphidoletes aphidimyza Rondani. Research method: The melon aphid was reared on cucumber plants treated with different levels of nitrogen (0, 100, 150, and 200 kg per hectare). In order to study the demography of A. aphidimyza, its immature and adult periods were daily investigated on cucumber leaves infested by the melon aphid. The length of different periods, survival, and the number of deposited eggs by adults was recorded on different treatments. Standard errors of the population growth parameters were calculated by the Jackknife method and the data analysis were done by SPSS software. To study the functional response, varying densities (2, 4, 6, 8, 12, 16, and 24) of the second and third instars of the melon aphid were separately offered to the 4-day old larvae of A. aphidimyza, which were starved for 10 h. The number of consumed preys was recorded after 18 h. The type of functional response and the estimate of parameters were performed by SAS software. Both experiments were carried out at 25 ± 1 °C, 60 ± 5 % RH and 16 L : 8 D in a growth chamber. Findings: Based on the results, different levels of nitrogen did not significantly affect the various development period of A. aphidimyza, but significantly influenced the population growth parameters of the predator. The intrinsic rate of natural increase (rm) of A. aphidimyza ranged from 0.1087 to 0.1399 day-1 on different treatments, which was highest on the treatment of 200 kg per hectare and lowest on non-fertilized treatment. The highest amount of finite rate of increase (λ) was also obtained on the level of 200 kg per hectare. Based on the results, the functional response of A. aphidimyza on different nitrogen levels was type II. Attack rate (a) of A. aphidimyza varied from 0.0623 to 0.1512 h-1 and its handling time (Th) ranged from 1.4646 to 1.8716 h on different treatments. The highest amount of attack rate was obtained on the treatment of 200 kg per hectare Conclusion:: Increasing the dosage of nitrogen in cucumber plant, especially using 200 kg nitrogen per hectare can be useful in reducing the melon aphid population by increasing the population growth rate and attack rate of A. aphidimyza.

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