Phenology of the black bean aphid, Aphis fabae, on organic crops and effect of parasitoid communities

Abstract

Abstract Parasitoids represent the third trophic level in plant‐insect food webs. They develop in or on herbivorous insects at the second trophic level, which in turn feed on plants that constitute the first trophic level. This food web system might be affected by agricultural landscape and practices. We studied the phenology and population density of Aphis fabae (Hemiptera: Aphididae) and determined the impact of parasitoids in organic fields of beans and beet plants. Twenty leaves per field were collected weekly. For each leaf, the total number of aphids, apterous and alate morphs, the number of mummies, and mortality of aphids were recorded. Our results showed that the phenology of A. fabae varied throughout the season with maximal numbers observed at the beginning of summer. In addition, the production of alate morphs and the proportion of parasitism were positively correlated to an increase in aphid densities. Six parasitoid species were recorded attacking A. fabae in the field, with Lysiphlebus fabarum and Binodoxys angelicae (Hymenoptera: Aphidiinae) being the most abundant parasitoids. Field characteristics and availability of host plants in the surroundings affected A. fabae density. Lysiphlebus fabarum and B. angelicae appeared to be good biocontrol candidates against A. fabae.