Geographic Variation in Pinus ponderosa Susceptibility to the Gouty Pitch Midge, Cecidomyia piniinopsis, in the Sierra Nevada and Southern Cascade Mountains of California : Insects Affecting Reforestation. Biology and Damage

1989

S. 205-212

1 Abb., 4 Lit. Ang.

Unselbständiges Werk

200069388

Geographic variation in susceptibility to the gouty pitch midge, Cecidomyia piniinopsis O.S. (Diptera: Cecidomyiidae), was analyzed in 3-year- old ponderosa pine, Pinus ponderosa Doug. ex Laws., seedlings in an outdoor nursery in the central Sierra Nevada. In this study, 472 families of phenotypically superior, windpollinated seed trees from the species range in the Sierra Nevada and southern Cascade Mountains of California were represented. Trees with viscid (resinous) spring shoot surfaces were more often injured by gouty pitch midge than those with nonviscid (smooth or waxy) surfaces. Susceptibility was based on mean family scores for shoot surface and gouty pitch midge injury. Analysis of these families in relation to latitude, longitude, and elevation of the seed source revealed a complex geographic pattern. Suceptibility of families from the northern Sierra Nevada and southern Cascades was relatively low and increased only moderately at the northern, eastern, and southern margins of the region. In the southern Sierra Nevada, susceptibility was higher, and increased with decreasing latitude. Longitudinal trends in susceptibility to goutyp pitch midge were not evident in this region. Watered seedlings had more gouty pitch midge injuries than unwatered, but there was no evidence this differenceaffected gouty pitch midge susceptibility of families.