Appropriate Mesh Size of Insect Screen for the Exclusion of the Cigarette Beetle, Lasioderma serricorne (F.)

Insect screens are often used in tobacco facilities to exclude insect pests. Previous studies using laboratory cultures indicated that screens with openings smaller than 1.0 mm are adequate to prevent the passage of the cigarette beetle, Lasioderma serricorne. The beetles from natural populations are rather heterogeneous, and their body sizes may vary. Studies were conducted to confirm the relationship between mesh sizes and the body sizes of the cigarette beetles that can pass through the screens and to elucidate the size distribution of wild beetles. The results revealed that meshes can protect against beetles whose thorax width is larger than the openings in the mesh. Additionally, the widths of the prothoraxes of wild beetles captured in pheromone traps, which were generally considered to be male, ranged from 727–1070 μm (N = 169), and approximately 90% of the beetles had thoraxes that were narrower than 1000 μm. These data led to the conclusion that a 1.0 mm opening mesh is insufficient to protect against the cigarette beetle. Thus, Tyler standard #24 mesh (= US standard #25 mesh: 0.71 mm opening/sieve size) is recommended as an insect screen for tobacco facilities.