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The performance of the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae) was studied on several Fabaceae species including: pea (Pisum sativum), broad bean (Vicia faba), alfalfa (Medicago sativa), bean (Phaseolus vulgaris) and red clover (Trifolium pratense). Alfalfa, bean and red clover were less accepted by the pea aphid than pea and broad bean. The pea aphid fed on the alfalfa, bean and red clover showed longer pre-reproductive, and shorter reproductive and post-reproductive periods. Alfalfa, bean and red clover also shortened and decreased fecundity of the pea aphid. Mean survival of the pea aphids fed on red clover and bean plants was reduced in comparison to pea aphid fed on pea and broad bean. The other studied population parameters: intrinsic rate of natural increase (rm), net reproduction (R0) and mean generation time were also reduced in the case of the pea aphid on alfalfa, red clover and bean. The study of aphid development and reproduction demonstrated that pea and broad bean are suitable host plants for A. pisum while alfalfa, red clover and bean are not. It is likely that the rejection of alfalfa, red clover and bean by A. pisum was caused by chemical factors in these hosts.
Flavonoids are a group of secondary metabolites found in most families. They are known to have important physiological functions in plants by protecting them against biotic stresses. Liquid chromatography (HPLC) was used to determine the flavonoid profiles, especially apigenin glycosides, their total concentration, as well as changes in the amount of six flavones found in the aerial parts of alfalfa (Medicago sativa L.) (Fabaceae) Radius cv. for three vegetative stages, uninfested and infested by the pea aphid (Acyrthosiphon pisum Harris) (Homoptera: Aphididae). It has been shown that both control and infested green aerial parts of alfalfa plants had similar flavonoid profiles. The dominant flavonoid of alfalfa was compound 7-O-[2-O-feruloyl- β-D-glucuronopyranosyl(1→2)-O-β-D-glucuronopyranosyl]-4’-O-β-D-glucuronopyranosideapigenin. Compound 4’-O-β-D-glucuronopyranosideapigenin was present in the smallest amounts. The total concentration of flavones was rather high and ranged from 10.32 to 12.28 mg/g d.m., but there were no significant differences between uninfested and infested alfalfa plants. There was a negative correlation between the concentration of total apigenin glycosides in the alfalfa plants and pea aphid abundance and phloem sap ingestion. This finding may indicate the importance of apigenin glycoside forms as nutritional compounds.
Extensive studies have been carried out to identify plant phenolics with insecticidal properties towards insects. The subject of the study were comparison of control and infested by Acyrthosiphon pisum (Harris) vegetative parts of pea plants. In the pea plants six flavonol aglycones were identified: quercetin, kaempferol+RCO-, kaempferol, tricin, apigenin+RCO-, and apigenin. In infested plants relatively high concentration of total phenols, o-dihydroxyphenols and total flavonoids in comparison with control were observed. It suggests that phenolics have negative effect on insects and they are good for control of the insect pests.
The pea aphid (Acyrthosiphon pisum) presents a considerable threat to bean family plants. In order to determine its feeding preferences, the following plants were tested: field pea (Pisum sativum), common bean (Phaseolus vulgaris), soya bean (Glycine max), lentils (Lens culinaris), narrow-leaf lupine (Lupinus angustifolius), white lupine (Lupinus albus), yellow lupine (Lupinus luteus) and broad bean (Vicia faba). Selected biometric parameters were used to evaluate feeding acceptance. The results of performer experiment showed that pea and broad bean are more often infested and colonized by the pea aphid than soya bean, lentils or yellow lupine. Narrow-leaf lupine, white lupine and common bean are not exposed to pea aphid feeding and they are not make a suitable habitat for the development of this insect.
Two important lady beetle species commonly found in alfalfa fields in Iran are the variegated lady beetle Hippodamia variegata Goeze and the seven spotted lady beetle Coccinella septempunctata (Linnaeus, 1758) (Coleoptera: Coccinellidae). These two species attack many aphid species including the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). In this study, the seasonal population changes of A. pisum, H. variegata, C. septempunctata and the parasitoid, Dinocampus coccinellae (Schrank) (Hymenoptera: Braconidae) were studied in alfalfa fields in the 2012 and 2013 seasonal periods. The highest ladybird densities were noted on July 5, 2012 and on September 6, 2013 (17.2±2.8 and 13.4±1.6) individuals per 20 sweeps, respectively. Parasitism rates by D. coccinellae ranged from approximately 3 to 6% in two subsequent years, respectively. Parasitism was higher early in the growing season. Most parasitised ladybirds were females. There was no significant relationship between the temperature and relative humidity with pea aphid populations, although the aphid populations declined during the hot summer period. In contrast, the relationship between temperature and the H. variegata population was significant and positive in both years of the study. It has been shown that these lady beetle species have a major role in reducing the pea aphid populations in alfalfa fields. Due to the relatively low percentage of field parasitism by D. coccinellae, this parasite might not reduce the biocontrol efficiency of lady beetle species.
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