Four parameters of the wound response of loblolly and shortleaf pines to inoculation with the blue-staining fungus associated with the southern pine beetle

摘要

The wound response of loblolly,Pinus taedaL., and shortleaf,P.echinataMill., pine was examined for 14 days following wounding and inoculation of the trees withCeratocystis minor(Hedgecock) Hunt, a fungal associate of the southern pine beetle,Dendroctonus frontalisZimmermann. Lesion length increased at a constant rate during June, while during July there was an initially rapid lesion formation followed by a leveling off for both tree species. Lesion enlargement occurred faster from days 2 through 7 in July for both species, and at the end of the 14-day study periods, the loblolly pines had a longer average lesion length than did the shortleaf pines during both months. During June, there was an initial increase in resin flow rate followed by a decrease in resin flow rate for several days and then an increased resin flow rate to levels similar to or above the rate measured prior to wounding. During July, the initial increase in resin flow rate following inoculation was not observed. Average soluble-sugar content decreased and monoterpene concentration increased in the lesion inner bark tissue. Inner bark monoterpene composition also changed, with the percentage of alpha;-pinene increasing or remaining unchanged in loblolly pine and decreasing in the shortleaf pine. The observed differences in tree response to fungal invasion may be important in determining if an individual can repel or impede invasion byD.frontalisat different times during the summer.