| چکیده انگلیسی مقاله |
Introduction: Rose (Rosa hybrida (L.), Rosaceae) has been grown on earth for millions of years and has been used for beauty and decoration of gardens, extraction of perfume and in medicine. But main use of roses is in cut flower industry and landscaping. Roses are attractive for insects, especially aphids (2, 3, 5, 6, 7, 11, 17, 27, 28, 35, 38). Among them, the predominant aphid that feeds on the cultivated roses in outdoors is the rose aphid, Macrosiphum rosae (13, 27, 28, 29). The rose aphid has a wide distribution throughout Iran and the world (27, 28, 29). Rose aphids generally initiate feeding on roses in early spring as the new flush of growth emerges. Like other aphid species, rose aphids tend to congregate or cluster in large numbers feeding on the terminal growth including leaves and stems, and developing flower buds, and on leaf undersides. Their feeding causes deformity flower buds and leaves which may result in flower buds aborting or falling off prematurely before opening. In addition, aphids secrete honeydew, which attracts ants, wasps, hornets and serves as a growing medium for certain black sooty mold fungi. Rose aphids are attacked by anvarray of natural enemies including parasitoids and predators such as ladybird beetles, green lacewings, syrphids and several other groups of arthropods. These may provide natural regulation depending on the number of rose aphids present and other biotic and abiotic factors. Although many herbivorous arthropods may attack roses but many roses cultivar can resist against these pests (23, 26, 28, 40). An important factor influencing this success is careful selection of varieties, which vary significantly in susceptibility to pests and disease problems (9, 13, 19, 21, 23, 30, 40). Of course, other factors such as agricultural practices and the presence and activities of natural enemies of pests are also important. This study aimed to determine any resistance against rose aphid in different rose cultivars in landscapes of Mashhad and also to determine the diversity and abundance of the rose aphid predators throughout the seasonal growth in the study area. Material and Methods: Research to investigate the resistance of different rose cultivars against rose aphid and the biodiversity of its predators was conducted at the campus of Ferdowsi University of Mashhad from Mid-March of 2013 to late march 2014. Six rose cultivars including Ice berg, Miniature, Josephine bruce, Piccadilly, Fairy & Blessing were sampled weekly in three sampling sites. For sampling, four cut sections (5 centimeters of terminal part of randomly selected shoot) of each cultivar in each site were cut and put in a plastic bag and brought to the laboratory for counting the number of different stages of rose aphid as well as the associated predators. For purpose of identification of immature stages of the aphid predators, immature stage was kept until they reach to adult stage in the laboratory. Results and Discussion: A seasonal fluctuation of rose aphid was recorded throughout the season on six rose cultivars (Table 1). Overall, this aphid was more numerous in spring and early fall on all studied cultivars (Figure 1). By approaching the summer, the population of rose aphid on all rose cultivars, except the Fairy and Miniature varieties declined to zero. Analysis of variance showed that differences in mean population of rose aphid among studied cultivars was significant (P< 0.01). Overall the season, minimum and maximum average aphid populations (12.65± 6.8 & 62.25± 28.9) were found on Ice berg & Blessing cultivars, respectively. Among different aphid predators found at colonies of rose aphids on different cultivars, Syrphidae and Coccinellidae with 39.9 & 30.2 percent were the most abundant groups. The most abundant aphid predators in sampling sites were Coccinella septumpunctata, Hypodamia variegatae (Coccinellidae) and Paragus bicolor and Syrphus ribesii (Syrphidae). Conclusion: In this study the mean population of rose aphid on Ice berg cultivar was lower than other rose cultivars, implying some resistance against aphids in this rose cultivar. Population size of rose aphid fluctuates in time and space due to a variety of reasons, such as fluctuations in environmental conditions, changes in quality of host plant and impact of natural enemies. Considering the economic importance of the rose aphid, using natural enemies which are compatible with environmental conditions of the given area integrated with resistant varieties of roses can reduce the application of pesticides against rose aphids in green spaces. Further researches on efficiency of natural enemies of rose aphid as well as on determining resistance of roses to aphids are recommended. |