Differences in Monterey pine pest populations in urban and natural forests

Abstract

Monterey pines ( Pinus radiata D. Don) planted along streets (i.e. street trees) within Carmel, California and its immediate vicinity, and naturally grown Monterey pine within adjacent native stands, were sampled with regard to intensity of visual stress characteristics, western dwarf mistletoe ( Arceuthobium campylopodum f. typicum [Engelm.] Gill), and western gall rust ( Peridermium harknessii J.P. Moore) infection, and frequency of sequoia pitch moth ( Synanthedon sequoiae Hy. Edw.) and red turpentine beetle ( Dendroctonus valens LeConte) attacks. The street trees were stratified into four geographic zones: one highly urban zone, two urban zones, and one suburban zone. Dwarf mistletoe infections generally were more common in the forest stand than on street trees in the highly urban and urban zones for trees less than 50 cm dbh and were positively correlated with stand density. Pitch moth attacks were more common in all street tree zones than the natural forest, and were positively correlated with amount of pruning and wounding, and negatively correlated with amount of crown closure and stress. Red turpentine beetle attacks were positively correlated with stress and diameter, and may follow pitch moth attacks. More beetle attacks occurred in the two urban zones than in the natural forest, probably due to significantly more large trees in these zones, and more pruning and wounding in the street tree setting than in the forest.