C. Wayne Berisford

Association between severity of prescribed burns and subsequent activity of conifer-infesting beetles in stands of longleaf pine

A randomized complete block experiment was performed to measure the effect of prescribed, dormant-season burns of three different levels of severity (measured as fuel consumption and soil surface heating) on subsequent insect infestation and mortality of mature longleaf pine (Pinus palustris Mill.). Multiple-funnel traps baited with a low release rate of turpentine and ethanol were used to monitor activity of certain coniferophagous beetles. Non-aggressive species, including the root beetles Hylastes salebrosus Eichhoff and H. tenuis Eichhoff, the ambrosia beetle Xyleborus pubescens Zimmermann, the reproduction weevil Pachylobius picivorus (Germar), and buprestid borers, were attracted to burned plots in numbers that correlated positively with burn severity. Beetle attraction to burned sites was greatest in the first weeks post-burn and disappeared by the second year. Two potential tree-killing bark beetles, Dendroctonus terebrans (Olivier) and Ips grandicollis (Eichhoff), were trapped in significant numbers but exhibited no attraction to burned plots. Tree mortality correlated significantly with the severity of the burns and amounted to 5% of stems in the hottest burn treatment after 3 years. The majority of the mortality was observed in the second and third years post-burn. Attacks of Ips and Dendroctonus bark beetles were apparent on nearly all dead or dying trees, and evidence suggested that root pathogens may have contributed to tree susceptibility to beetle attack and mortality. Our data indicate that selection of burn regimes that reduce or eliminate consumption of duff (e.g., favoring heading fires over backing fires) could significantly reduce mortality of longleaf pine managed for long rotations.

Attraction of the bark beetle parasitoid Roptrocerus xylophagorum (Hymenoptera: Pteromalidae) to host-associated olfactory cues

Abstract Studies were conducted to identify host location cues used by Roptrocerus xylophagorum (Ratzeburg), a larval/pupal parasitoid of bark beetles. In Y-tube olfactometer bioassays, female R. xylophagorum were attracted to infested bark (i.e., phloem, cambium, and outer corky bark tissues) removed from bolts of loblolly pine, Pinus taeda L., colonized by the late instar larvae and pupae of the bark beetle Ips grandicollis Eichhoff (Coleoptera: Scolytidae). In contrast, bark taken from recently cut, uninfested bolts interrupted attraction to infested bark when these were presented together. Larval and pupal hosts isolated from infested bark were not attractive to parasitoids, whereas frass removed from the larval mines in infested bark was highly attractive. Bark from which hosts or both hosts and host frass were removed remained highly attractive. Bark sandwiches (fresh bark with the exposed surface pressed to glass microscope slides) infested with either third-instar or adult female I. grandicollis were attractive to female parasitoids, whereas bark sandwiches with only mechanical damage to the phloem tissue were unattractive. A steam distillate of bark infested with host larvae was attractive to female R. xylophagorum, whereas a distillate of fresh pine resin was not attractive. Volatiles from the experimental baits were collected on Porapak Q and analyzed by coupled gas chromatography-mass spectrometry. Several compounds were identified that distinguished baits with biological activity. These data show the importance of the complete host/plant complex for attraction of R. xylophagorum to its host’s habitat and suggest a possible role for particular odors from uninfested host plant tissue in directing foraging parasitoids away from locations with few or no hosts.

Pheromones in white pine cone beetle, Conophthorus coniperda (Schwarz) (Coleoptera: Scolytidae)

Female white pine cone beetles,Conophthorus coniperda, attacking second-year cones of eastern white pine,Pinus strobus L., produced a sex-specific pheromone that attracted conspecific males in laboratory bioassays and to field traps. Beetle response was enhanced by host monoterpenes. The female-produced compound was identified in volatiles collected on Porapak Q and in hindgut extracts as (+)-trans-pityol, (2R,5S)-(+)-2-(1-hydroxy-1-methylethyl)-5-methyltetrahydrofuran. Males and females produced and released the (E)-(-)-spiroacetal, (5S,7S)-(-)-7-methyl-1,6-dioxaspiro[4.5]decane, which was not an attractant for either sex, but acted as a repellent for males. Porapak Q-trapped volatiles from both sexes contained (+)-trans-pinocarveol and (-)-myrtenol. In addition, hindgut extracts of females containedtrans-verbenol, while males had pinocarvone and verbenone. Work in Georgia and Canada confirmed that the same isomers of pityol and spiroacetal are present in two distinct and widely separated populations ofC. coniperda.

THE NANTUCKET PINE TIP MOTH

The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), is one of the most common forest insects in the eastern United States. It was first discovered and studied on Nantucket Island, Massachusetts,63 where it was causing severe damage to pines and was described as the “frustrating Retinia” (= Rhyacionia).23 The taxonomic status of R. frustrana is generally clear except for its relationship with R. bushnelli Miller, thought by some to be a subspecies.59 The primary difference is that R. frustrana overwinters in infested shoots and R. bushnelli overwinters in the duff and soil beneath the trees.

Monoterpene oviposition stimulants ofDioryctria amatella in volatiles from fusiform rust galls and second-year loblolly pine cones.

Volatiles collected on Poropak Q from fusiform rust galls (Cronartium quercuum F. sp.fusiforme) of loblolly pine for 3 hr were better ovi-position stimulants forDioryctria amatella (Hulst) females than extracts of 8-hr collections. GLC analysis of these extracts showed no major differences in relative monoterpene composition, although 8-hr collections contained an unidentified compound not detected in the 3-hr collections. Comparison of volatiles from second-year loblolly pine cones with those from fusiform galls showed that both containeddl-α-pinene, (−)-β-pinene, myrcene, and (+)-limonene. Camphene was found in galls only, and relatively large quantities of β-phellandrene were identified only from cones. The five major monoterpenes found in the two host substrates were tested in an oviposition bioassay. Eighteen trials using different combinations of these terpenes showed that the combination of α-pinene, myrcene, and limonene was as attractive toD. amatella females as all other terpene combinations, including turpentine.

Use of cuticular hydrocarbons in bark beetle parasitoid taxonomy: A study of Roptrocerus xylophagorum (Ratzeburg) (Hymenoptera: Torymidae) from the United States, Europe and Australia

Abstract Cuticular hydrocarbons of adult Roptrocerus xylophagorum (= eccoptogastri ) (Ratzeburg) from California and Georgia were isolated and characterized by combined gas chromatography-mass spectrometry. The hydrocarbon compositions of individuals from both locations were very similar with the major components of n-alkanes, midchain-methylbranched alkanes, terminally methylbranched alkanes and 3,7-dimethylbranched alkanes. Hydrocarbons of the females were shorter (average chain length 28.7) than the hydrocarbons recovered from the males (31.5). Cuticular hydrocarbons of R. xylophagorum females from Belgium, Austria and Switzerland were primarily alkenes, n-alkanes and alkadienes, whereas the major components of males from Belgium were n-alkanes, alkenes and terminally methylbranched alkanes. Cuticular hydrocarbon profiles of R. xylophagorum collected in Europe were very different from those of R. xylophagorum from the United States but very similar to Roptrocerus mirus collected in Switzerland. R. xylophagorum adults from Australia that were progeny of those introduced from the United States had cuticular lipid profiles similar to those of the parasitoids collected in North America.

Field evaluations of potential aggregation inhibitors for the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae)

Semiochemicals that inhibit the response of the southern pine beetle, Dendroctonus frontalis Zimmermann, to its aggregation pheromone have been used with varying degrees of success to protect indiv...

An olfactometer for bark beetle parasites

An “H”-type olfactometer was designed and built to test the response of bark beetle parasites to various beetle and tree host odors. The design has several advantages over other types of olfactometers. Strong air currents are not utilized, parasites have free movement in the test chamber, and a concentration gradient of test compound is maintained. Parasites tested in the olfactometer demonstrated strong positive responses to air drawn over logs infested with bark beetle larvae and varied responses to tree host odors.

Predicting Infestation Levels of the Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) Using Pheromone Traps

Abstract There is considerable interest in using pheromone trap catches of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), to estimate or predict population density and damage. At six sites in the Georgia Piedmont, adult tip moths were monitored through one or more years using pheromone traps while population density and damage for each tip moth generation were determined. During most years, trap catch was higher during the first adult generation compared with subsequent generations regardless of population density. Within each generation, trap catch was moderately to highly correlated with associated population density or damage levels. Hyperbolic regression models best described these relationships and suggested trap saturation when populations are high. Trap catch during the first adult generation was highly predictive of population density or damage during the subsequent generation. Trap catch during the second adult generation was fair at predicting subsequent density or damage. The models presented herein should be used with caution because they are likely to be region-specific. Validation of these relationships is necessary before widespread application of these models is warranted.

Nantucket pine tip moth Rhyacionia frustrana: identification of two sex pheromone components.

Two compounds identified as components of the sex pheromone system ofRhyacionia frustrana are (E)-9-dodecen-1-yl acetate (I) and (E)-9,11-dodecadien-1-yl acetate (II), which were found in female gland extracts in the ratio of 96∶4, respectively. The identifications were based on chemical and instrumental analyses, electroantennogram studies, and field trapping tests. The optimum ratio for trapping maleR. frustrana is the range of 95∶5 to 97.5∶2.5 (I∶II), when dispensed from rubber septa at a loading of ca. 1000/μg/lure. In addition to these two compounds, evidence was obtained for the presence of dodecan-1-ol and (E)-9-dodecen-1-ol in female tip extracts and in female effluvium, and for dodecan-1-yl acetate in female tip extracts.