Pea leaf weevil herbivory on pea seedlings: effects on growth response and yield
1995
Williams, Livy | Schotzko, D.J. | O'Keeffe, L.E.
Field experiments were conducted to determine growth and yield responses of Pisum sativum L. to defoliation by adult Sitona lineatus (L.). Seedlings grown under conventional (moldboard plowed) and conservation (chisel plowed) tillage treatments were infested for a 1-week period with 0, 1 and 8 weevils per plant at two times: at 75% field emergence and 1 week later. After the early infestation, defoliation for the control, low and high weevil densities was about 0, 15 and 50%, respectively, while defoliation after the late infestation was about 0, 10 and 35%. An undercompensatory growth response was observed in one experiment after seedlings were subjected to moderate levels of early defoliation. Exact compensation was observed in two experiments after early infestations of low and high Sitona densities. Sitona defoliation reduced the number of pods per plant and pod length in two experiments. However, seed biomass was never significantly reduced. Averaged over all experiments, reduction in seed biomass due to high Sitona densities was 10 and 5% for early and late infestations, respectively. Tillage treatments did not affect Pisum compensatory growth response, although yield components were sometimes greater in conservation tillage than in conventional tillage, possibly due to slightly greater soil moisture in the conservation tillage plots.
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