Fumigation of Insect-Infested Wooden Logs by EDN Using Two Scenarios of Plastic Tent-Tarpaulin Sealing: Wooden Logs Stacks Placed on Bottom Plastic Sheets or Directly on Underlying Soil

Abstract

Recently, the largest bark beetle calamity (Ips typographus) of the last 100 years has erupted in Central Europe, including the Czech Republic. This calamity may threaten the sustainability of growing large areas of monoculture Norway spruce (Picea abies) in this area. Limited economically feasible physical and chemical pest control options are available to prevent the bark beetle spread. However, from these options, only mechanical bark removal or gas-insecticide fumigation result in instant deactivation of all pest stages throughout the entire stack of stored logs. Due to the ban on the use of methyl bromide (MeBr) for the fumigation of log piles under tarpaulin, the adaptation of the phyto-quarantine method EDN to the destruction of I. typographus bark beetles in harvested wood directly in forests was newly proposed in the Czech Republic. The methodical experience with fumigation of the harvested logs, however, was only available for wood fumigation in chambers or in tent-tarps fumigation placed on paved (concrete/asphalt) surfaces mainly in ship harbors. Prior to the introduction of the new EDN fumigation method of bark beetle infested wood stored directly in the forests, it was initially unclear whether it was necessary to use or neglect bottom sheets to optimize exposure and maximize Ct products for the permitted fixed initial dose (50 g·m−3). Therefore, the initial validation pilot trials were aimed at the estimation and comparison of EDN temporal dynamics and Ct products under real forest conditions and two fumigation scenarios: Wooden log pile placed on bottom plastic sheets or directly on soil without the bottom sheets. Field trials were performed under both identical as well as different environmental conditions. In addition, they revealed that the concentration decrease was significantly faster and Ct products were significantly lower in the case of trials without the bottom sheets. The experiments indicated high EDN sorption by the uncovered soil under the tent. Quantitatively, the average Ct product was 4.8 (identical conditions) and 3.7 (different conditions) times lower in EDN trials without the bottom sheets when compared to the use of bottom sheets. The initial field-forest fumigation validation trials indicated a necessity to carry out EDN fumigation under tent-tarps also using bottom sheets, although this fumigation procedure increases the labor-demands to some extent. Based on the presented results and additional data, the Czech authority issued for the EDN plant protection product an authorization for the limited and controlled use of wooden logs. Therefore, this work became the basis of the historically and first officially authorized use of any fumigant for pest control under commercial forest conditions.