Bark borer Semanotus japonicus (Col., Cerambycidae) utilization of Japanese cedar Cryptomeria japonica: a delicate balance between a primary and secondary insect

Abstract

The bark borer, Semanotus japonicus (Col., Cerambycidae), attacks living Japanese cedar, Cryptomeria japonica, with newly hatched larvae mainly feeding within the inner bark of the trunk. To understand how S. japonicus is affected by host nutrition and resin flow, newly hatched larvae were introduced into stressed cedar trees. Stress was induced by either heavy pruning, stem cutting (i.e. removing the side branches and top of tree), or girdling. Larval mortality due to resin flow in the ‘heavy pruning treatment’ and the ‘stem cutting treatment’ tended to be lower than that in the untreated control cedar trees where all larvae were drowned by resin flow. Parasitism to the larval stage was observed in the stem‐cutting trees, not in living trees, suggesting that S. japonicus may avoid parasitism in living cedar trees because few volatiles are produced. In the ‘stem‐girdling treatment’, although more than 90% of the introduced larvae died due to poor nutrition below the girdle, 7.8% of the larvae above the girdle reached the adult stage. The live body weight of the adults collected from above the girdle was similar to those taken from naturally infested cedar trees. These results suggest that S. japonicus requires adequate host nutrition but that larvae are defenceless against high resin flow. Thus, S. japonicus seems to be in a transition state between being primary or secondary with respect to its attack behavior on living cedar trees.

Influence of Host Tree Condition on the Performance ofTetropium fuscum(Coleoptera: Cerambycidae)

“…Moisture or drought stress can reduce oleoresin exudation pressure (Mattson and Haack 1987b) and the production of induced oleoresin in conifers (Croisé and Lieutier 1993, Cobb et al 1997, Lombardero et al 2000 and also may cause qualitative changes in oleoresin composition (Hodges and Lorio 1975). Oleoresin is an important mechanism of resistance for conifers (Phillips and Croteau 1999), and reductions in its quantity or quality can increase the performance of phloeophagous insects and associated fungi (Berryman 1972, Mattson and Haack 1987b, Paine et al 1997, Shibata 2000, Tisdale et al 2003. This may explain the high rates of T. fuscum apparent survival on caged, girdled trees in this study.…”

“…As predicted, parasitoids foraged more often or more efÞ-ciently on cut and girdled than on apparently healthy trees. Parasitism of another longhorn beetle, S. japonicus, was also lower in untreated than in mechanically stressed trees (Shibata 2000). An increase in parasitism on stressed trees may result from primary attraction of parasitoids to stressed tree volatiles (Sullivan et al 1997, Pettersson 2001, Rojas et al 2006, as foraging on stressed trees may increase their likelihood of Þnd-ing host insects that colonize these trees.…”

“…For example, drought stress may promote outbreaks of herbivorous insects (Mattson and Haack 1987a), and herbivore abundance and performance often vary with host plant growth rate . Variations in herbivore performance on host plants of varying condition may be caused directly by quantitative or qualitative variation in herbivore nutrition Lorio 1969, White 1984); by host plant resistance to attack, or both (Christiansen et al 1987); or indirectly because host plant condition may mediate the impact of natural enemies (Shibata 2000, Paine et al 2001) and competitors (Ohgushi 2005). Thus, many insect herbivores are adapted to colonize hosts of a particular physiological condition, which is often associated with their feeding guild (Larsson 1989).…”

Evaluating Seasonal Variation in Bottom-Up and Top-Down Forces and Their Impact on an Exotic Wood Borer,Tetropium fuscum(Coleoptera: Cerambycidae)

“…Studies on the ecology of wood borers that attack living hosts usually measure interactions between two immediate trophic levels, with only rare consideration given to tri-trophic interactions (e.g., Shibata 2000). In this study, topÐ down forces and competition were negligible, but herbivore performance and induced host defenses were strongly inßuenced by both host condition (a bottomÐ up factor) and the timing of herbivore attack.…”

Plant damage from and defenses against ‘cryptic’ herbivory: A guild perspective

“…The biomass of stems above the girdled section rarely survive the damage, causing a loss of 6 Á13 cm of stem growth even before the wood-boring larvae begin to feed. Such 'indirect' effects are often magnified by the length of time that borers spend within the plant; it can take a year or more before pupation occurs and adults emerge (Strauss 1991, Shibata 2000. The effect of RSBs is similar to that of sea urchins in the strongly cascading otter-urchin-kelp system (Estes & Palmisano 1974, Estes & Duggins 1995: urchins kill large amounts of kelp by eating the connective tissue at the base of the algal blades, severing the holdfast and allowing the floating biomass above it to drift away.…”