Longitudinal study of Caribbean pine elucidates the role of 4-allylanisole in patterns of chemical resistance to bark beetle attack

Southern pine beetles (Dendroctonus frontalis Zimmermann) and symbiotic fungi are associated with mass mortality in stands of Caribbean pine (Pinus caribaea Morelet). This study provides a 12.7-year assessment of semiochemical mediation between southern pine beetle and Caribbean pine in relation to concentrations of 4-allylanisole (estragole, methyl chavicol) and monoterpenes measured by gas chromatography–mass spectrometry in different seasons in premontane and coastal pine stands of Belize and Guatemala. Individual trees and stands with >2.5% (relative mass %) of 4-allylanisole in the xylem oleoresin exhibited significantly less beetle-induced mortality than those with <2.5%. Changes in relative levels of 4-allylanisole and monoterpenes during this study are consistent with seasonal temperature and cumulative water deficit effects and suggest bark beetle attack of P. caribaea may intensify in the future.

Retention Time in Three Nursery Container Volumes Impacts Root Architecture

Four general-use insecticides (Astro®, Onyx®, Dominion® Tree & Shrub, and Xytect 2F®) were evaluated for their effectiveness at preventing attacks by the southern pine beetle (SPB) (Dendroctonus frontalis) and the small southern pine engraver (Ips avulsus) using a previously developed small-bolt method. Evaluations were conducted between 58 and 126 days post treatment. Southern pine beetles from New Jersey and Mississippi, U.S., were evaluated using a mixture of field and laboratory small-bolt trials; beetle origin did not appear to affect results. Astro and Onyx bole sprays were effective at reducing or eliminating attack by SPB, while the imidacloprid soil drench products (Dominion and Xytect) were ineffective. With I. avulsus in Louisiana, U.S., Astro was effective at reducing bole utilization at 58 and 83 days posttreatment but failed at 126 days. Onyx, Dominion, and Xytect were ineffective against I. avulsus in these tests. Imidacloprid phloem residues averaged 0.74 (μg/g phloem dry weight) for Dominion and 1.31 for Xytect, values that are similar to other studies but low for purposes of control. These results support previous findings that systemic imidacloprid is ineffective for protecting pines against Dendroctonus bark beetles and that bole sprays with bifenthrin or permethrin can be effective. However, permethrin was the only active ingredient that was effective against I. avulsus in the current study.

Evaluation of General-Use Insecticides for Preventing Host Colonization by New Jersey Southern Pine Beetles

Four general-use insecticides (AstroR, OnyxR, DominionR Tree & Shrub, and Xytect 2FR) were evaluated for their effectiveness at preventing attacks by the southern pine beetle (SPB) (Dendroctonus frontalis) and the small southern pine engraver (Ips avulsus) using a previously developed small-bolt method. Evaluations were conducted between 58 and 126 days post treatment. Southern pine beetles from New Jersey and Mississippi, U.S., were evaluated using a mixture of field and laboratory small-bolt trials; beetle origin did not appear to affect results. Astro and Onyx bole sprays were effective at reducing or eliminating attack by SPB, while the imidacloprid soil drench products (Dominion and Xytect) were ineffective. With I. avulsus in Louisiana, U.S., Astro was effective at reducing bole utilization at 58 and 83 days posttreatment but failed at 126 days. Onyx, Dominion, and Xytect were ineffective against I. avulsus in these tests. Imidacloprid phloem residues averaged 0.74 (μg/g phloem dry weight) for Dominion and 1.31 for Xytect, values that are similar to other studies but low for purposes of control. These results support previous findings that systemic imidacloprid is ineffective for protecting pines against Dendroctonus bark beetles and that bole sprays with bifenthrin or permethrin can be effective. However, permethrin was the only active ingredient that was effective against I. avulsus in the current study.

High-resolution analysis of stem increment and sap flow for loblolly pine trees attacked by southern pine beetle

Manual and automated dendrometers, and thermal dissipation probes were used to measure stem increment and sap flow for loblolly pine (Pinus taeda L.) trees attacked by southern pine beetle (Dendroctonus frontalis Zimm.) in east Tennessee, USA. Seasonal-long measurements with manual dendrometers indicated linear increases in stem circumference from April through June. Changes in stem circumference slowed after this time, and further increases were either modest or not observed. These effects coincided with a massive midsummer infestation of trees with southern pine beetles. High-resolution measurements with automated dendrometers confirmed that, while early-season increases in radial increment were positive, daily rates of radial increment for slow- and fast-growing trees were largely negative in early to late July. Sap velocity also declined despite favorable weather conditions, but these reductions were not observed until mid-August. Thus, effects on radial increment and stem circumference preceded those on sap velocity by several weeks. The timing of these events, combined with the known developmental rate of southern pine beetles, suggest that disruption of whole-tree water balance is not a prerequisite for the success of attacking beetles or for oviposition by colonizing females and larval development, all of which were completed by early August. Additional field experiments that use high-resolution techniques to measure stem increment and sap flow are needed to more rigorously characterize temporal changes in host physiology during initial invasion and colonization of trees by southern pine beetle.