Impact of certain weather factors and plant age on the population density of Aphis craccivora (Koch) on faba bean plants.

Abstract
Field studies were done on faba bean plants at the El-Mattana Agricultural Research Station in Luxor Governorate, Egypt, throughout two successive growing seasons (2019/20 and 2020/21) to investigate the seasonal activity of the cowpea aphid, Aphis craccivora (Koch) (Hemiptera: Aphididae) (Giza 843 cultivar). As well, estimate the effects of some climatic conditions and plant ages on the seasonal abundance of A. craccivora. In this study, two insect expressions were used, i.e., insect numbers and incidence of infestation, which articulated the population of this pest. Results indicated that A. craccivora infested faba bean plants from 21st November 2019 to 12th March 2020 during the first growing season and from 22nd November 2020 to 13th March 2021 through the second one. For the two growing seasons, the cumulative counts of A. craccivora were 321.48 and 340.66 individuals each season, respectively. Furthermore, the overall mean of A. craccivora population was 18.91 ± 0.92 and 20.04 ± 1.52 individuals per 10 plants, during the first and second growing seasons, respectively. As well, the general average of the percentages of abundance was 66.73 ± 1.60 and 58.43 ± 2.28 for the two seasons, respectively. Climatic conditions of weekly inspection dates were more favourable for A. craccivora to increase its population in November, January and February for the two seasons. Additionally, in two consecutive growing seasons, the number of A. craccivora disappeared during the faba bean maturation stage in end March. According to the findings, the combined impacts of environmental conditions and plant ages can explain changes in A. craccivora population density. The results revealed that the effects of weather conditions and plant ages on population density and infestation incidence percentages by A. craccivora were highly significant during the two seasons studied, and that these parameters varied from season to season. Also, the dew point and mean daily minimum temperature were the most effective variable for the changes in the insect population and the percentages of infestation incidences under the studied seasons. These information can aid in the development of an aphid IPM program for faba bean plants.