Effects of continuous UV-B stress on biological characteristics of green pea aphid

Ozone depletion resulted in enhanced UV-B stress in middle and high latitude regions in the northern and southern hemispheres. This situation had generally been a key factor of pea aphid’s genetic divergence. Pea aphid (Acyrthosiphum pisim) which transmiting many different plant viruses is a main species of harmful pests. It can cause significant loss to agriculture, particularly the production of alfalfa (Medicago spp.), pea (Pisum sativum), vicia faba (Vicia faba) and other crops. To determine the effect continuous UV-B stress on the development and population parameters of pea aphid and to provide theoretical basis for ecological heredity and population succession and integrated pest management, 8 generations of green pea aphid nymph born for 12 h were treated by UV-B 40 W. The treatment included 6 times per generation, once per day, 6 days per generation, and respectively 20 min, 30 min, 40 min, 50 min and 60 min per treat. The life parameters of the intrinsic rate (r_m), net reproductive rate (R₀), mean generation time (T) and finite rate of increase (λ) were determined for reared singles. The results showed that nymph development duration increased with added radiation time or generation, with the longest duration of 8.11 d. the lifetime of adult aphid extended initially and then shortened. Compared with the control, the lifetime of the eight generation (F₈) was only 6.71%21.27% of the control. Net reproductive rate increased and then decreased, with F8 of 0.20%22.32% of the control. The intrinsic rate of F₈ declined obviously, with the high of 11.05% of the control. The finite rate increased and then shortened, with F₈ of 0.90%22.14% of the control. Mean generation time of F₈ shortened by 8.54%21.11%, compared with that of the control. Based on development and population parameters of the tested green pea aphid under continuous UV-B stress, green pea aphid grew well at its 4th generation irrespective of the period of time of UV-B stress treatment. However, the more was the generation added, the more was the increase in the process time of the same generation and the more was the inhibiting effect on the development and reproduction of green pea aphids, eventually slowing the increase in population growth.