Effects of mass inoculation on induced oleoresin response in intensively managed loblolly pine

Abstract

Oleoresin flow is an important factor in the resistance of pines to attack by southern pine beetle, Dendroctonus frontalis Zimm., and its associated fungi. Abiotic factors, such as nutrient supply and water relations, have the potential to modify this plant-insect-fungus interaction; however, little is known of the effects of inoculation with beetle-associated fungi on oleoresin flow. We observed that constitutive and induced resin yield in loblolly pine, Pinus taeda L., were affected by either fungal inoculation (with the southern pine beetle-associated fungus Ophiostoma minus (Hedgcock) H. & P. Sydow) or silvicultural treatment. The effects of mass wounding (400 wounds m(-2)) and mass wounding and inoculation with O. minus were assessed by comparison with untreated (control) trees. The treatments were applied to trees in a 2 x 2 factorial combination of fertilizer and irrigation treatments. Fertilization did not significantly affect constitutive resin yield. Even as long as 105 days post-treatment, however, mass-inoculated trees produced higher induced resin yields than control or wounded-only trees, indicating a localized induced response to fungal inoculation. We noted no systemic induction of host defenses against fungal colonization. Although beetles attacking previously attacked trees face a greater resinous response from their host than beetles attacking trees that had not been previously attacked, the effect of an earlier attack may not last more than one flight season. Despite mass inoculations, O. minus did not kill the host trees, suggesting that this fungus is not a virulent plant pathogen.

The Role of Phytopathogenicity in Bark Beetle–Fungus Symbioses: A Challenge to the Classic Paradigm

“…In addition, this fungus is not specific to the bark beetle, as it is found with many bark beetles including species that colonize weakened, dying, or dead trees (47,64,101). This fungus initiates a moderate induced defense response in pines (22,40,51,75).…”

“…Notably, observations that O. minus was not always present, or present only in small amounts, in trees killed by D. frontalis brought into question the role of this fungus in tree killing. Furthermore, inoculation studies indicated that O. minus is not capable of killing mature pines (51). Perhaps most revealing were observations that tunneling larvae of D. frontalis turn away from phloem colonized by O. minus and do not survive when they cannot avoid feeding in O. minus-colonized areas (6,63).…”

HISTOPATOLOGÍA DEL PINO DE LAS ALTURAS (Pinus hartwegii Lindl.) INOCULADO CON TRES HONGOS OPHIOSTOMATOIDES

“…These affirmations are confirmed in the present study. Furthermore, the inoculation technique, the amount of inoculum and the physiological state of the tree can have an influence in the tree being easily colonized (Klepzig et al, 2005).…”

Analysis of cellulase and polyphenol oxidase production by southern pine beetle associated fungi

“…A appears to be more beneficial) and are carried within specialized structures called mycangia, in the beetle. Ophiostoma minus (Hedgcock) H. and P. Sydow is a socalled bluestain fungus which aids the beetle in depleting host defences (Klepzig et al, 2005), but later acts antagonistically, competing with the mycangial fungi and larvae for uncolonized phloem (Barras, 1970;Klepzig and Wilkens, 1997).…”