Threshold of Spodoptera litura on Vigna angularis
Japanese scientists carried out experiments to determine the threshold of Spodoptera litura (EPPO A1 pest) on Vigna angularis.
It was found that the average S. litura consumed an average leaf area of 204 cm2 of which 82% were consumed by the final instar.
Based on this defoliation it was determined that the tolerance injury level was 5% or two final instar larvae per plant.
Sources
Katayama, J. ; Sano, K. (1989) Damage analysis of red bean plants caused by the common cutworm, Spodoptera litura (Lepidoptera: Noctuidae).
Japanese Journal of Applied Entomology and Zoology 33, 57-62.