Can. Ent. 107: 251-256 (1975) Observations were made on the flight patterns, sex ratios, and ovipositional activity of Pissodes strobi in Sitka spruce. There is an aggregation of adults on spruce leaders early in the flight season during which sexual maturation and mating take place. Males are more active early in the flight season, while females are more numerous during the latter half of the flight season.
Application. Lygus hesperus Knight caused apical bud abortion in 1-0 and 2-0 Douglas-fir (Pseudotsuga menziesii (Mirb .) Franco) seedlings in forest nurseries in western Oregon .Reduction of this damage can be accomplished by introducing nursery management practices for lygus control . Such practices include chemical control and modification of seedling physiology or phenology . Our results also suggest that lygus management in forest nurseries must address immigration from nearby crops, especially alfalfa and cotton .
Abstract . Causes of apical bud abortion in Douglas-fir (Pseudotsuga menziesii (Mirb .) Franco)were examined in two nurseries in western Oregon . Insect and damage surveys indicated that leafhoppers and Lygus hesperus Knight increased in abundance during August and September, coincident with damage accumulation. Caging studies confirmed that L . hesperus can cause bud abortion and indicated that nymphs of this insect could complete development to maturity on Douglas-fir seedlings .
Vapor pressure deficit (VPD) regimes were determined for Sitka spruce (Piceasitchensis (Bong.) Carr.) plantations growing in coastal and inland sites of the Olympic Peninsula of Washington State. Relationships between VPD regimes on patterns of stomatal conductance, stem hydration, and xylem pressure potential were examined in Sitka spruce saplings growing on these two sites. These patterns and VPD regimes were analyzed in relation to areas known to sustain either low or high infestation levels of the tip weevil (Pissodesstrobi (Peck) (Coleoptera: Curculionidae)). High VPD regimes of inland Sitka spruce plantations were frequently observed in the summers and were associated with clear days and on-shore breezes; in synchrony with high VPD regimes, the trees of these areas exhibited water stress and decreased photosynthesis. In turn, these factors might contribute to lowered host defenses against tip weevil attacks. Coastal sites generally experienced lower VPD regimes and, consequently, infrequent water stress and stomatal closure, and spruces growing near the coast were mostly associated with low tip weevil attack.
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