Spatial and Temporal Distribution of Imidacloprid in Eastern Hemlock in the Southern Appalachians

Abstract

The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is an exotic insect species dramatically reducing populations of eastern hemlock, Tsuga canadensis (L.) Carrieré, throughout the eastern United States. Systemic imidacloprid is one of the primary chemicals used to successfully control infestations of the hemlock woolly adelgid. The concentration levels for this systemic insecticide present in the sap of eastern hemlocks were evaluated from three strata within the canopy over a two year time span. Enzyme-linked immunosorbent assays were conducted every three months posttreatment to assess imidacloprid concentration within the sap. The effect of application timing (fall versus spring) and application method (soil drench, soil injection, and tree injection) on the translocation of imidacloprid throughout the canopy, and the quantity of imidacloprid translocated in the sap of eastern hemlock branches and the terminal twig and needle tissue was determined. Concentration levels progressively declined from the bottom strata to the top strata of the canopy. This trend was consistent in all chemically treated trees. Tree injections provided the lowest concentration and the most nonuniform distribution of imidacloprid throughout the canopy. The highest insecticide concentrations within the tree across all strata over the two year period were consistently associated with the soil drench method followed by the soil injection method. Imidacloprid concentrations peaked between month 9 and 12 posttreatment, and then declined; however, at two years posttreatment, soil drench and soil injected trees contained concentrations reported as being effective for control of the hemlock woolly adelgid.

Assessment of risks and potential of injection techniques in integrated programs to eradicate the red palm weevil: review and new perspectives

“…A large part of the debate on injection is not about the possible harmful consequences M. Ferry and S. Gomez for the health of the treated tree with this technique but about its efficacy and cost [29,31,[60][61][62][63][64][65][66][67][68][69][70][71][72][73].…”

Concentration Levels of Imidacloprid and Dinotefuran in Five Tissue Types of Black Walnut, Juglans nigra

“…In a two-year study monitoring the translocation and concentrations of imidacloprid in eastern hemlock, significantly higher concentrations of imidacloprid were found in the lower stratum compared to the upper [26]. In addition, 293 insect species were documented to be associated with eastern hemlock and at least 33 species were impacted initially by systemic imidacloprid treatments [30].…”

“…Additionally, little is known about the imidacloprid metabolite, olefin-imidacloprid, which is reported to be more toxic than imidacloprid [25], and it is unknown at what levels and for how long olefin-imidacloprid can remain within deciduous plant material, including nutmeat. Although research has been conducted on the spatial and temporal movement of imidacloprid in eastern hemlocks, Tsuga canadensis L., [26], it is important to understand the movement of imidacloprid and its derivative chemicals, i.e., olefin-imidacloprid, through black walnuts if they are going to be considered for control of wood-boring insects associated with TCD. Therefore, the objective of this project is to document the translocation and within-tree concentrations of imidacloprid and dinotefuran within various types of black walnut tissue, including leaves, twigs, trunk core, nut husk, and nutmeat, as well as track the movement and concentration levels of olefin-imidacloprid within nut husk and nutmeat tissue.…”

Influence of Hemlock Woolly Adelgid Infestation Levels on Water Stress in Eastern Hemlocks within the Great Smoky Mountains National Park, U.S.A.

“…Eastern hemlocks under drought stress and those with needle loss and dieback have difficulty transporting systemic insecticides into the canopy [20]. This difficulty may be the result of low transpiration rates of stressed leaves, which limits the uptake and movement of water.…”

“…This difficulty may be the result of low transpiration rates of stressed leaves, which limits the uptake and movement of water. Reduction of adelgid populations as the result of imidacloprid treatment has been shown to dramatically increase new growth, resulting in the recovery of trees that had been in poor condition, although the rate of recovery is highly dependent on the health of the tree at the beginning of treatment as well as the degree of water stress [20]. Translocation of imidacloprid has been shown to occur in eastern hemlock throughout the entire canopy, and has been shown to persist for more than two years [20]; however, trees in that study were under minimal drought stress and low infestation levels of hemlock woolly adelgid prior to treatment.…”