Simple Is Best: Pine Twigs Are Better Than Artificial Lures for Trapping of Pine Weevils in Pitfall Traps

The large pine weevil Hylobius abietis (Linnaeus 1758) is the main pest of coniferous seedlings in Europe and causes substantial damage in areas that have been clear-cut or otherwise disturbed. We compared the efficacy of different attractants for the capture of H. abietis adults in white pitfall traps. The field experiment was performed from mid-April to the end of August 2018 at six plots in Central Europe located in spruce stands that had been clear-cut. At each plot, we compared five attractants: one pine twig with ethanol, Hylodor, alpha-pinene + ethanol, turpentine oil and ethanol (separated), and turpentine oil + ethanol (not separated). Traps without attractant served as a control. Six traps for each attractant or control were distributed at each plot. Of the total number of H. abietis adults trapped, 43.3%, 20.5%, 17.9%, 9.8%, 8.5% and 0.5% were captured in traps with pine twigs with ethanol, alpha-pinene, Hylodor, turpentine, oil + ethanol (separated), turpentine oil + ethanol (combined), and no attractant, respectively. The bottom of each trap contained propylene glycol to kill and preserve beetles. The small number of beetles captured in the control traps confirms that the propylene glycol:water mixture did not influence the trapping of H. abietis. The use of pitfall traps with a suitable attractant (especially pine twigs and ethanol) should be useful for monitoring of H. abietis, because it is simple and cost-effective. The use of such pitfall traps to control H. abietis by mass trapping would require 50 to 100 traps per ha

Drought or Severe Drought? Hemiparasitic Yellow Mistletoe (Loranthus europaeus) Amplifies Drought Stress in Sessile Oak Trees (Quercus petraea) by Altering Water Status and Physiological Responses

European oak species have long been considered relatively resistant to different disturbances, including drought. However, several recent studies have reported their decline initiated by complex changes. Therefore, we compared mature sessile oak trees (Quercus petraea (Matt.), Liebl.) infested versus non-infested by hemiparasitic yellow mistletoe (Loranthus europaeus Jacq.) during the relatively dry vegetation season of 2019. We used broad arrays of ecophysiological (maximal assimilation rate Asat, chlorophyll a fluorescence, stomatal conductance gS, leaf morphological traits, mineral nutrition), growth (tree diameter, height, stem increment), and water status indicators (leaf water potential Ψ, leaf transpiration T, water-use efficiency WUE) to identify processes underlying vast oak decline. The presence of mistletoe significantly reduced the Ψ by 1 MPa, and the WUE by 14%. The T and gS of infested oaks were lower by 34% and 38%, respectively, compared to the non-infested oaks, whereas the Asat dropped to 55%. Less pronounced but significant changes were also observed at the level of photosystem II (PSII) photochemistry. Moreover, we identified the differences in C content, which probably reduced stem increment and leaf size of the infested trees. Generally, we can conclude that mistletoe could be a serious threat that jeopardizes the water status and growth of oak stands