Species diversity of natural enemies and density of dominance pest in strip-intercropping corn and tomato with sainfon in Miandoab region

Zarei, Elham (2020) Species diversity of natural enemies and density of dominance pest in strip-intercropping corn and tomato with sainfon in Miandoab region. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

Abstract: The present study was conducted in two separate sections. In one section, the influences of corn monoculture (C), sainfoin monoculture (S) and strip-intercropping of corn with sainfoin in the four replacement ratios: 2C: 2S, 2C: 4S, 2C: 6S and 2C: 8S were evaluated on the population density of the European corn borer, diversity and abundance of its natural enemies and yield of both crops in an experimental field during 2016 and 2017. According to our results, intercrops caused a significant reduction in the number of TLM eggs, larvae and galleries and promoted a marked increase in the values of Shannon diversity index (H') for the species composition of TLM predators. Orius niger (Wolff) and Nesidiocoris tenuis (Reuter) were the dominant TLM predators recorded. Moreover, larval parasitoids Bracon hebetor Say and Neochrysocharis formosus (Westwood) were found to be more abundant relative to the other parasitoids in both 2016 and 2017. The larval parasitism rate was higher in intercrops than in tomato monoculture. On the other hand, the land equivalent ratio (LER) in intercrops was greater than one specifically, in 1T:2S (1.22 in 2016 and 1.17 in 2017) and 2T:2S (1.22 in 2016 and 1.19 in 2017). These findings demonstrated that intercropping tomato with sainfoin particularly, in 1T: 2S and 2T: 2S row ratios were effective in controlling T. absoluta in tomato fields. In other section, the influences of corn monoculture (C), sainfoin monoculture (S) and strip-intercropping of corn with sainfoin in the four replacement ratios: 2C: 2S, 2C: 4S, 2C: 6S and 2C: 8S were evaluated on the population density of the European corn borer, diversity and abundance of its natural enemies and yield of both crops in an experimental field during 2016 and 2017. Our results indicated that the densities of eggs and larvae of this pest decreased significantly in the intercrops especially in 2C: 6S and 2C: 8S compared with corn monoculture. The Shannon diversity index for predators in the intercrops was significantly greater than that in the corn monoculture. Moreover, the percentage of parasitized eggs and larvae were higher in the intercrops, especially in 2C: 6S and 2C: 8S, compared with the corn monoculture. Furthermore, the percentage of infested plants was also lower in 2C: 6S and 2C: 8S compared the other treatments. On the other hand, high values of land equivalent ratio were found in 2C: 6S (1.16 in 2016 and 1.15 in 2017) and 2C: 8S (1.17 in 2016 and 1.16 in 2017). Therefore, it could be concluded that 2C: 6S and 2C: 8S intercrops are useful in integrated management of the European corn borer in fields. Keywords: Pest population, natural enemies, yield, species richness, species abundance.

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