Derek Chartrand

Chemical and biomonitoring to assess potential acute effects of Vision herbicide on native amphibian larvae in forest wetlands.

In conjunction with operational forest herbicide spray programs in Ontario, Canada, chemical and biological monitoring studies were conducted in 51 different wetlands to quantify the probability and magnitude of contamination by a glyphosate herbicide formulation (Vision). Wetlands were classified as oversprayed, adjacent, or buffered in relation to the operational target spray blocks. Results show that vegetated buffers significantly mitigated against exposure and thus potential for acute effects. Aqueous concentrations of glyphosate in buffered wetlands were below analytical limits of quantitation (0.02 mg acid equivalent [a.e.]/L) in 14 of 16 cases, with mean concentration (0.03 +/- 0.02 mg a.e./L) significantly (p < 0.05) less than that of either adjacent (0.18 +/- 0.06 mg a.e./L) or oversprayed wetlands (0.33 +/- 0.11 mg a.e./L). Biomonitoring with caged amphibian larvae showed no significant differences among mean mortality (48 h) of either Rana pipiens (p = 0.194) or Rana clamitans larvae (p = 0.129) exposed in situ to Vision under these various wetland conditions. Percent mortality was not significantly (p = 0.05) correlated with exposure concentrations for either amphibian species tested. Results suggest that exposures typically occurring in forest wetlands are insufficient to induce significant acute mortality in native amphibian larvae.

Effects of Vision® herbicide on mortality, avoidance response, and growth of amphibian larvae in two forest wetlands

The effects of Vision (glyphosate, 356 mg acid equivalents (a.e.)/L) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans and Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands of northern Ontario, Canada. In addition to untreated controls, Vision was applied to yield initial concentrations ranging from 0.29 to 14.3 mg a.e./L (0.94-46.1 mg/L of Vision). Resultant 96-h median lethal concentration (LC50) values ranged from 2.70 to 11.5 mg a.e./L (8.71-37.1 mg/L of Vision) depending on the species or site involved. Substantial mortality and incidences of abnormal avoidance response occurred only at concentrations exceeding the expected environmental concentrations (EEC) (1.43 mg a.e./L, or 4.61 mg/L of Vision) as calculated by Canadian regulatory authorities. The concentration dependence of larval growth rate and maximum size varied depending on site and species. Mean growth rates and maximum sizes exposed to 1.43 mg a.e./L (EEC) treatments were the same or greater than controls. Experimental site and biotic/abiotic factors therein, such as pH and suspended sediments, substantially affected the expression of Vision herbicide toxicity in the amphibian larvae tested. Overall, results suggest that the silvicultural use of Vision herbicide in accordance with the product label and standard Canadian environmental regulations should have negligible adverse effects on sensitive larval life stages of native amphibians.

Environmental safety to decomposer invertebrates of azadirachtin (neem) as a systemic insecticide in trees to control emerald ash borer.

The non-target effects of an azadirachtin-based systemic insecticide used for control of wood-boring insect pests in trees were assessed on litter-dwelling earthworms, leaf-shredding aquatic insects, and microbial communities in terrestrial and aquatic microcosms. The insecticide was injected into the trunks of ash trees at a rate of 0.2 gazadirachtin cm(-1) tree diameter in early summer. At the time of senescence, foliar concentrations in most (65%) leaves where at or below detection (<0.01 mg kg(-1) total azadirachtin) and the average concentration among leaves overall at senescence was 0.19 mg kg(-1). Leaves from the azadirachtin-treated trees at senescence were added to microcosms and responses by test organisms were compared to those in microcosms containing leaves from non-treated ash trees (controls). No significant reductions were detected among earthworm survival, leaf consumption rates, growth rates, or cocoon production, aquatic insect survival and leaf consumption rates, and among terrestrial and aquatic microbial decomposition of leaf material in comparison to controls. In a further set of microcosm tests containing leaves from intentional high-dose trees, the only significant, adverse effect detected was a reduction in microbial decomposition of leaf material, and only at the highest test concentration (∼6 mg kg(-1)). Results indicated no significant adverse effects on litter-dwelling earthworms or leaf-shredding aquatic insects at concentrations up to at least 30 × the expected field concentrations at operational rates, and at 6 × expected field concentrations for adverse effects on microbial decomposition. We conclude that when azadirachtin is used as a systemic insecticide in trees for control of insect pests such as the invasive wood-boring beetle, emerald ash borer, resultant foliar concentrations in senescent leaf material are likely to pose little risk of harm to decomposer invertebrates.

Foliar residue dynamics of azadirachtins following direct stem injection into white and green ash trees for control of emerald ash borer

BACKGROUND Azadirachtins are natural insecticides derived from the neem tree. The emerald ash borer (EAB) is an exotic invasive insect pest that infests various ash tree species and has the potential for significant economic, aesthetic and ecological impacts throughout North America. The initial translocation and foliar residue dynamics of azadirachtins were examined following direct injection into white and green ash trees growing in urban scenarios as a potential control for EAB. RESULTS Substantial concentrations of azadirachtins A and B [mean maxima > 0.98 mg kg(-1) fresh weight (f.w.)] were observed within 2 days of injecting a specifically designed formulation of azadirachtins. Foliar residues declined exponentially through time, with half-life estimates ranging from 5.1 to 12.3 days. At the time of leaf senescence, foliar residue levels approximated 0.01 mg kg(-1) f.w., strongly mitigating the potential effects of non-target biota in soil or aquatic compartments. CONCLUSION The magnitude and duration of exposures observed in this field study were considered to be above the thresholds required for biological effectiveness against both larval and adult life stages of EAB. Results support the use of azadirachtins as an environmentally acceptable systemic insecticide for control of EAB and protection of high-value ash trees in urban environments.

Integrating advanced technologies for optimization of aerial herbicide applications

Aerial application of herbicides continues to be a dominant method of vegetation control in Canadian forest management. In this paper, we describe a suite of relatively modern technologies and emphasize their potential for integrated use in optimization of aerial herbicide treatments. The potential is illustrated using several case studies involving fixed-wing applications of glyphosate-based herbicide in the boreal forest region of Ontario, Canada. Results indicate that integration of geographic information systems, differential global positioning, electronic-guidance, on-site meteorological monitoring and remote sensing can be used to effectively plan, enhance application control and provide detailed post-treatment assessment and archival data for herbicide spray programs. SprayAdvisor, a GIS-based decision support system with the capacity to directly integrate all of these elements is briefly described.

Analytical study of azadirachtin and 3-tigloylazadirachtol residues in foliage and phloem of hardwood tree species by liquid chromatography-electrospray mass spectrometry.

A rapid and sensitive LC-ESI-MS method has been developed and validated for the quantitation of azadirachtin and 3-tigloylazadirachtol in deciduous tree matrices. The method involves automated extraction and simultaneous cleanup using an accelerated solvent technique with the matrix dispersed in solid phase over a layer of primary-secondary amine silica. The limits of quantification were 0.02 mg/kg for all matrices with the exception of Norway maple foliage (0.05 mg/kg). Validation at three levels (0.02, 0.1, and 1 mg/kg), demonstrated satisfactory recoveries (71-103%) with relative standard deviation <20%. Two in-source fragment ions were used for confirmation at levels above 0.1 mg/kg. Over a period of several months, quality control analyses showed the technique to be robust and effective in tracking the fate of these natural botanical insecticides following systemic injection into various tree species for control of invasive insect pest species such as the emerald ash borer and Asian longhorned beetle.

DNA metabarcoding and morphological macroinvertebrate metrics reveal the same changes in boreal watersheds across an environmental gradient

Cost-effective, ecologically relevant, sensitive, and standardized indicators are requisites of biomonitoring. DNA metabarcoding of macroinvertebrate communities is a potentially transformative biomonitoring technique that can reduce cost and time constraints while providing information-rich, high resolution taxonomic data for the assessment of watershed condition. Here, we assess the utility of DNA metabarcoding to provide aquatic indicator data for evaluation of forested watershed condition across Canadian eastern boreal watersheds, subject to natural variation and low-intensity harvest management. We do this by comparing the similarity of DNA metabarcoding and morphologically derived macroinvertebrate metrics (i.e. richness, % Ephemeroptera, Plecoptera and Trichoptera, % chironomid), and the ability of DNA metabarcoding and morphological metrics to detect key gradients in stream condition linked to forested watershed features. Our results show consistency between methods, where common DNA metabarcoding and morphological macroinvertebrate metrics are positively correlated and indicate the same key gradients in stream condition (i.e. dissolved oxygen, and dissolved organic carbon, total nitrogen and conductivity) linked to watershed size and shifts in forest composition across watersheds. Our study demonstrates the potential usefulness of macroinvertebrate DNA metabarcoding to future application in broad-scale biomonitoring of watershed condition across environmental gradients.

Deposition of azadirachtin following ultra-low volume aerial applications to red pine plantations for control of pine false webworm, Acantholyda erythrocephala (L.) (Hymenoptera: Pamphiliidae), in Ontario, Canada

A completely randomized experimental design was employed to assess differences in on-target deposition of azadirachtin A following aerial applications of Fortune AZA 3% (50 g a.i. ha−1) to three red pine plantations infested with pine false webworm (Acantholyda erythrocephala (L.)). Substantial differences in mean foliar deposits were observed among plantations. However, these differences were not statistically significant owing to high variability in deposits within spray blocks. All mean deposits were well in excess of levels generating 91% mortality in laboratory bioassays against pine false webworm. In relation to a second objective, poor and occasionally insignificant correlation between deposits on natural foliage and two types of artificial collectors indicated that neither collector was effective in estimating true foliar deposition. Our results suggest that aerial applications of undiluted azadirachtin formulations at nominal rates of 50 g a.i. ha−1 yield foliar deposits in red pine canopies sufficient to induce high mortality in pine false webworm populations. Strict control over application parameters (track spacing, upwind offset and flight-line orientation) is necessary to minimize deposit variation.

Author Correction: DNA metabarcoding and morphological macroinvertebrate metrics reveal the same changes in boreal watersheds across an environmental gradient

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Erratum to: Integrating advanced technologies for optimization of aerial herbicide applications

Unfortunately, In the original publication under the Section ‘‘Results and discussion’’ the sentence in the 6th paragraph for the subheading ‘‘Remote sensing with true color digital or near infra-red satellite imagery’’ is incorrectly published. The sentence should read ‘‘This result provides substantive scientific support for the standard minimum buffer zone width of 60 m as reasonable for protection of sensitive aquatic habitats.’’