كليدواژه :
كشت نواري , فراواني گونه‌ها , غناي گونه‌ها , شكارگر , پارازيتيسم
چكيده فارسي :
در تحقيق حاضر تاثير پنج نوع سيستم كشت نواري ذرت (C) و آفتابگردان (S) شامل 2C: 2S، 4C: 2S، 8C: 2S، 4C: 4S، و 2C: 4S به همراه تك كشتي ذرت در تراكم كرم ساقه خوار اروپايي ذرت، Ostrinia nubilalis (Hübner)، تنوع گونه هاي دشمنان طبيعي آن، درصد تخم ها و لاروهاي پارازيته شده و عملكرد محصول ذرت در مزرعه آزمايشي واقع در منطقه اردبيل در سال هاي 1395 و 1396 مطالعه شد. تراكم مراحل نابالغ (تخمها، لاروها و شفيره ها ) اين شبپره در تيمارهاي كشت نواري به طور معني داري كمتر از تك كشتي ذرت بود.در بين دشمنان طبيعي Orius niger (Wolff)، Lydella thompsoni Herting، Bracon hebetor Say و Trichogramma brassicae Bezdenko درصد فراواني نسبي بالايي را در سيستم هاي كشت مورد مطالعه داشتند. شاخص تنوع شانون (H') در تيمارهاي كشت نواري ذرت و آفتابگردان به طور معني داري بيشتر از تك كشتي ذرت بود. مقادير محاسبه شده شاخص شباهت تنوع گونه هاي موريسيتا- هورن (CMH) براي تركيب گونه هاي شكارگرها بين سيستم هاي كشت نواري 946/0 ≥CMH در سال 1395 و 934/0 ≤CMH در سال 1396 بود. در هر دو سال، درصد تخم ها و لاروهاي پارازيته شده O. nubilalis در تيمارهاي كشت نواري به طور معني داري بيشتر از تك كشتي ذرت بود.بيشترين عملكرد محصول ذرت و كمترين درصد كاهش عملكرد محصول ذرت در تيمار 8C: 2S مشاهده شد. بنابراين، مي توان نتيجه گيري كرد كه كشت نواري 8C: 2Sمناسب ترين نوع سيستم كشت براي استفاده در برنامه هاي مديريت تلفيقي O. nubilalis در مزارع ذرت مي باشد.
چكيده لاتين :
Background and Objectives
The European corn borer, Ostrinia nubilalis (Hübner), is an important pest of corn in Iran. Intercropping systems has been proposed as one approach that can be used for reducing pest density and improving biodiversity of natural enemies and crop yield. Therefore, the present research assessed the densities of immature stages of O. nubilalis, biodiversity of its predators, and parasitism rates of immature stages in experimental plots where corn was grown either as monoculture or strip-intercropped with sunflower. We also evaluated the effect of the intercropping systems with natural infestation of O. nubilalis on corn yield.
Materials and Methods
In this research, the influence of five strip-intercropping systems of corn (C) and sunflower (S)including 2C: 2S, 4C: 2S, 8C: 2S, 4C: 4S, and 2C: 4S along with corn monoculture was studied on density of imaginal stages of O. nubilalis, its natural enemies biodiversity, the percentage of parasitized eggs and larvae, and the grain yield of corn and the percentage of grain yield loss in an experimental field in Ardabil region in 2016 and 2017. These experimets were conducted in a randomized block design with four replicates.
Results
The densities of imaginal stages (eggs, larvae and pupae) of O. nubilalis in intercrops were significantly lower than corn monoculture. Among the natural enemies of this moth, Orius niger (Wolff), Lydella thompsoni Herting, Bracon hebetor Say and Trichogramma brassicae Bezdenko had the high relative abundance in the tested cropping systems. The Shannon diversity index (H') in intercrops was significantly greater than in corn monoculture. The calculated values of Morisita–Horn index for the predator’s species composition between intercrops were CMH ≥ 0.946 in 2016 and CMH ≥ 0.934 in 2017. In both years, the percentage of parasitized eggs and larvae of O. nubilalis in intercrops was significantly higher than in corn monoculture. The highest grain yield of corn and the lowest percentage of grain yield loss of corn were found in 8C: 2S intercrop.
Discussion
Based on the resource concentration hypothesis, the lower density of O. nubilalis and the lower percentage of infested plants in the intercropping systems of corn and sunflower could be demonstrated by overlapping of the secreted volatile compounds of two crops that caused disruption in the host finding. Moreover, based on the enemies hypothesis, the higher attraction and conservation of predators and parasitoids in intercrops caused lower density of O. nubilalis than in corn monoculture. In this study, the competition for nutriants between corn and sunflower was also reduced with increasing of the corn rows between the sunflower rows; the percentage of grain yield loss of corn was reduced in 8C: 2S copmpared to other intercrops. Therefore, it could be concluded that 8C: 2S intercrop is the most suitable intercropping system for use in integrated management of O. nubilalis in corn fields.
