Gouty Pitch Midge Damage to Ponderosa Pines Planted on Fertile and Infertile Soils in the Western Sierra Nevada

Book excerpt: Crown damage caused by gouty pitch midge (GPM) and its effects on tree growth were assessed in two 14-year-old ponderosa pine plantations, one on a shallow, infertile soil derived from serpentine and the other on a deeper, more fertile nonserpentine soil of marine parent material. Seed sources for each plantation were nearby indigenous stands on the same soils. Trees in both plantations had either viscid (resinous) or nonviscid surfaces on spring shoots. Light to moderate GPM damage was found in both plantations. Trees of both seed sources grew much faster in the nonserpentine than in the serpentine plantation. And in the serpentine plantation, the serpentine seed source grew faster than the nonserpentine seed source. But both fast- and slowgrowing trees had similar levels of GPM damage. Both direct and inverse relationships between GPM damage and growth of trees within seed sources occurred in both plantations, thus there was little evidence that GPM damage had affected tree growth on either site. In all comparisons, trees with viscid shoot surfaces had more GPM damage than trees with nonviscid shoots, a difference not previously reported for plantations with locally adapted seed sources.