Abiotic and biotic factors affecting southern pine health at landscape-level

Southern pine stands in Georgia (23 stands) and Alabama (15 stands) were measured for the effects of abiotic and biotic factors on pine health. We visited stands that were both asymptomatic and symptomatic. We recorded several abiotic variables, tree health and growth, and collected root samples from select trees in each stand. Root samples are being screened for the presence of Leptographium and Heterobasidion root fungi. Once data collections are complete, we will test for correlations between the presence of abiotic variables, root pathogens, and tree health on a landscape level. We hope this information will provide insight as to the prevalence and significance of pine health issues.

Field sampling is now complete, and Dr. David Coyle and Ms. Brittany Barnes are completing QA/QC on all data.  Soil chemical analyses are nearly complete, and soil texture analyses are complete.  All fungal culturing work is complete, and we are collaborating with Dr. Michael Wingfield’s lab at the University of Pretoria, South Africa, in an effort to achieve taxonomic resolution on the Leptographium spp. fungi.  Once all data are complete, manuscript preparation will begin, likely in spring 2015.

Relationships between tree health and root-feeding beetles

Using 18-21 year-old unthinned loblolly pine stands, we measured attraction of bark and woodboring insects (especially root-feeding weevils) to trees that were healthy, girdled, and baited with turpentine (a common lure for Hylastes weevils, the vectors of Leptographium fungi). Studies were conducted during three seasons in 2012-2013. Preliminary results indicate that very few beetles were attracted to healthy trees. The greatest number of beetles were attracted to girdled trees, followed by baited trees. These data suggest that maintaining healthy pine stands can reduce or eliminate the possibility of colonization by root-feeding weevils.

This project is now complete, and we are working to prepare these data for publication.  Manuscript preparation is being led by Ms. Christiane Helbig, a Ph.D. student from the Dresden University of Technology in Germany.

Landowner survey

To gauge the perceptions and knowledge of landowners, a survey was initiated for forest landowners in Georgia, South Carolina, and Florida. We will measure landowner knowledge regarding pine health and Southern Pine Decline, and their perceptions as related to the health of their pine stands. Upon completion of this project, we hope to be better able to assist landowners with their pine land management needs, and improve our outreach efforts.

Dr. David Coyle and Ms. Brittany Barnes are leading this project, with assistance from Dr. Gary Green.  Surveys have been sent out to potential respondents, and completed surveys are steadily being returned.  We hope to have this project completed by February 2015.

Future Research

Hylastes biology and ecology

Why do adults attack some trees and not others? What is the vector potential of adults? How much damage does larval tunneling really do to the tree? Does Hylastes attack without fungal inoculation affect tree health? Are Hylastes attacks without fungal inoculation even possible?

Effects of stressors on pine health

What are the effects of individual and multiple stressors on pine health? What combinations are the most detrimental to pine health? What is a tree's ability to recover from individual or multiple stressors?

Silviculture to improve stand health

Can silviculture be used to improve overall stand health regarding multiple insect attacks (southern pine beetle, Hylastes, etc.)? How does silviculture affect tree physiology and its inherent ability to fight off insect attacks?

Do effects of pine health issues carryover to subsequent rotations?

In stands that purportedly had Southern Pine Decline, were subsequently clear cut, and replanted with loblolly or longleaf pine, are those new stands more susceptible to pine health issues than stands on land that never showed Southern Pine Decline signs?