Contribution of Alate and Apterous Morphs to Demographic Characteristics, and Stable Stage Distribution of Acyrthosiphon pisum (Hemiptera: Aphididae) on Four Different Alfalfa Varieties.

Abstract

Life table data of the green pea aphid, Acyrthosiphon pisum (Harris) reared on four different resistant alfalfa varieties, i.e., 5S43, TG4 CW044026 (abbreviated as TG4), TG7 CW2883 (abbreviated as TG7), and Aurora were analyzed using the age-stage, two-sex life table. A higher proportion of alate adults were observed on 5S43, TG7, and Aurora; while a higher proportion of apterous adults occurred on TG4. The contributions of alate aphids to the finite rate of increase (λ), intrinsic rate of increase (r), and net reproductive rate (R0) were higher than apterous aphids on 5S43, TG7, and Aurora, while apterous aphids contributed more to λ, r, and R0 on TG4. The highest population parameters were observed on TG4 (r = 0.208 d-1, λ = 1.231 d-1, and R0 = 18.8 offspring/individual), while the lowest values were on TG7 (r = 0.129 d-1, λ = 1.138 d-1, and R0 = 9.9 offspring/individual). Because the age-stage, two-sex life table is capable of describing the stage differentiation, it enables the calculation of the stable stage distribution (SSD). A higher proportion of adult A. pisum was observed in SSD than in fourth instar nymphs. Population simulation showed the stage structure will approach SSD. Because the R0 and the mean generation time (T) values do not reflect the population growth rate, their use as population fitness parameters should be avoided. These findings can be utilized in helping to select resistant alfalfa varieties to effectively manage the pea aphid.