Geographical Variation in Response of Southern Pine Beetle (Coleoptera: Scolytidae) to Aggregating Pheromones in Laboratory Bioassays

by Dr. Molly Darr | Jun 16, 2022 | 1981-1990 Publications

Abstract

Attacks by Dendroctonus frontalis Zimmermann were prevented on southern pines by applications of lindane or chlorpyrifos to the entire bole and to the top half of the bole only. Treatment of the basal 2 m and the lower half of tree boles did not prevent attacks. By applying toxicants to only the top half of trees, insecticide volume was reduced by over 30%, and contamination of nontarget areas near the base of the trees was significantly reduced.

Keywords

Insecta, Dendroctonus frontalis, pheromones, geographical variation

To read the full article please visit the link below:

Selective Application of Insecticides for Prevention of Southern Pine Beetle Attack

by Dr. Molly Darr | Jun 16, 2022 | 1981-1990 Publications

Abstract

Attacks by Dendroctonus frontalis Zimmermann were prevented on southern pines by applications of lindane or chlorpyrifos to the entire bole and to the top half of the bole only. Treatment of the basal 2 m and the lower half of tree boles did not prevent attacks. By applying toxicants to only the top half of trees, insecticide volume was reduced by over 30%, and contamination of nontarget areas near the base of the trees was significantly reduced.

To read the full article please visit the link below:

Phenetic and Phylogenetic Relationships Among Ten Species of Dendroctonus Bark Beetles (Coleoptera: Scolytidae)

by Dr. Molly Darr | Jun 16, 2022 | 1981-1990 Publications

Abstract

Molecular genetic relationships among 10 species of Dendroctonus bark beetles were assessed using electrophoretic data from 18 gene loci. Cluster and distance Wagner analysis of these data showed a high level of similarity between D. pseudotsugae Hopkins and D. simplex LeConte, D. valens LeConte and D. terebrans (Olivier), and D. adjunctus Blandford and D. approximates Dietz. These groupings correspond generally to groups identified in earlier studies using anatomical, cytogenetic, and behavioral characteristics. The distance Wagner tree indicated that D. rufipennis (Kirby), D. adjunctus, and D. approximatus are the most primitive species. D. valens, D. terebrans, D. simplex, D. pseudotsugae, and D. frontalis Zimmermann appear to be the most evolutionarily advanced of the species studied.

To read the full article please visit the link below:

Effects of Heterobasidion annosum on Radial Growth in Southern Pine Beetle-Infested Loblolly Pine

by Dr. Molly Darr | Jun 16, 2022 | 1981-1990 Publications

Abstract

The association of Heterobasidion annosum with reduced radial growth was observed in loblolly pine (Pinus taeda) infested with southern pine beetle (SPB) (Dendroctonus frontalis). Plots with SPB and controls were established in thinned plantations and natural stands of loblolly pine. Only sites infested with SPB for less than 8 wk were selected for experimental evaluation. A control plot was established 20 m from each SPB plot. Trees infested with SPB produced an average of 6% less radial growth over the last 1-5 yr in the loblolly pine plantations as compared to the noninfested control plots (P = 0.05). Mean H. annosum colonization of excavated root systems in SPB and control plots in plantations were 23.1 and 10.9% (P = 0.05), respectively. Within the plots infested with SPB located in plantations, the SPB-infested trees produced 28% less radial growth for the last 1-5 yr, respectively, as compared to the noninfested trees (P = 0.01). Mean H. annosum colonization of excavated root systems in SPB-infested and noninfested trees in ht eSPB plots were 54 and 11% (P = 0.0001), respectively. It was concluded that loblolly pines preferred by SPB were being stressed by H. annosum prior to SPB attack and that this stress was being expressed through reduced radial growth.

Keywords

annosum root rot, Fomes annosus, radial growth, bark beetle, predisposition

To read the full article please visit the link below:

Development Time and Mortality of Dendroctonus frontalis in Relation to Changes in Tree Moisture and Xylem Water Potential

by Dr. Molly Darr | Jun 16, 2022 | 1971-1980 Publications

Abstract

Development time and observed mortality of Dendroctonus frontalis Zirnrn. in relation to changes in host-tree condition were studied in east Texas during the summer of 1977. Four indices of host condition were monitored: bark, phloem, and xylem moisture and twig xylem water potential. Successful attack initiated predictable patterns of drying and rehydration in the phloem and xylem, and increasingly negative water potentials at the branch tips. These patterns were described mathematically and correlated to beetle development time. Eggs and 1st stage larvae were not affected by changes in phloem moisture in individual trees. However, development of 2nd- and 3rd-stage larvae was slowed when phloem moisture stayed above ca. 170% oven dry weight prior to those stages. Development of 2nd- and 3rd-stage larvae was also slowed in trees exhibiting large decreases in phloem moisture during those stages. Larval mortality was greater than mortality to other life stages. Concurrently, changes in phloem moisture were greatest when larvae were developing. Bark moisture remained at ca. 30% oven dry weight throughout beetle development. Development of 4th stage larvae and pupae was slower in trees with high average bark moisture during those stages.

To read the full article please visit the link below: