Taylor Scarr

Imidacloprid in leaves from systemically treated trees may inhibit litter breakdown by non-target invertebrates.

Imidacloprid is a systemic insecticide that is used in trees to control several invasive, wood-boring insect pests in North America. Applications to deciduous trees result in foliar concentrations of imidacloprid that could pose a risk of harm to non-target decomposer invertebrates when autumn-shed leaves fall to forest floors or adjacent water bodies. Selection experiments were conducted in aquatic and terrestrial microcosms to test the hypothesis that non-target, leaf-shredding invertebrates can detect and avoid leaves from imidacloprid-treated trees thereby circumventing effects on leaf litter decomposition. There was no significant preferential feeding on non-contaminated leaves in selection microcosms indicating that the invertebrates could not detect and avoid imidacloprid-containing leaves. Mass loss and area consumed of both imidacloprid-containing and natural leaves in selection microcosms were significantly less than in control microcosms, indicating a sub-lethal feeding inhibition effect from consumption of leaf material at realistic field concentrations of 18-30microg/g fresh weight. Our results indicate that imidacloprid at realistic concentrations in leaves can inhibit leaf litter breakdown through adverse sub-lethal effects on decomposer invertebrates.

Evidence for a Volatile Pheromone in Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) that Increases Attraction to a Host Foliar Volatile

ABSTRACT Analysis by gas chromatography/mass spectrometry (GC/MS) of volatiles from virgin female emerald ash borer, Agrilus planipennis Fairmaire confirmed the emission of (3Z)-lactone [(3Z)-dodecen-12-olide] but not its geometric isomer, (3E)-lactone [(3E)-dodecen-12-olide]. Gas chromatographic/electroantennographic (GC/EAD) analysis of synthetic (3Z)-lactone, which contained 10% (3E) -lactone, showed a strong response of male and female antennae to both isomers. EAG analysis with 0.01 - to100-µg dosages showed a positive dose response, with females giving significantly higher responses than males. In field experiments with sticky purple prism traps, neither lactone isomer affected catches when combined with ash foliar or cortical volatiles (green leaf volatiles or Phoebe oil, respectively). However, on green prism traps, the (3Z)-lactone significantly increased capture of male A. planipennis when traps were deployed in the canopy. Captures of males on traps with both (3E)-lactone and (3Z)-hexenol or with (3Z)-lactone and (3Z)-hexenol were increased by 45–100%, respectively, compared with traps baited with just (3Z)-hexenol. In olfactometer bioassays, males were significantly attracted to (3E) -lactone, but not the (3Z) -lactone or a 60:40 (3E): (3Z) blend. The combination of either (3E)- or (3Z)-lactone with Phoebe oil was not significantly attractive to males. Males were highly attracted to (3Z)-hexenol and the (3Z)-lactone + (3Z)-hexenol combination, providing support for the field trapping results. These data are the first to demonstrate increased attraction with a combination of a pheromone and a green leaf volatile in a Buprestid species.

Community-level disruptions among zooplankton of pond mesocosms treated with a neem (azadirachtin) insecticide

A natural, plant-derived insecticide, neem, is being evaluated as an alternative insect pest control product for forestry in Canada. As part of the process to investigate the environmental safety of neem-based insecticides, a mesocosm experiment was conducted to assess the effects of neem on natural zooplankton communities. Replicate (n=5), shallow (<1 m) forest pond enclosures were treated with Neemix 4.5, at concentrations of 0.035 (the expected environmental concentration), 0.18, 0.70, and 1.75 mg/l active ingredient, azadirachtin. Zooplankton communities were quantitatively sampled over a 4-month experimental period in treated and control enclosures, and water samples were collected to track azadirachtin concentrations. Concentrations in water declined linearly with estimated DT(50) values of 25-29 days. Trends in abundance over time among populations of cladocerans, copepods, and rotifers were found to differ significantly among treatments. At the two highest test concentrations, adverse effects were obvious with significant reductions in several cladoceran species, and near elimination of the three major copepod species present. More subtle effects at the two lowest test concentrations were determined by comparing the community structure of enclosures across treatment levels and over time through an analytical process based on the multivariate statistical software, PRIMER. Significant effects on community structure were detected at both of these lower concentrations, including the expected environmental concentration of 0.035 mg/l azadirachtin. Differential responses among species (some increases, some decreases) caused detectable disruptions in community structure among zooplankton of treated enclosures. Perturbations to zooplankton communities were sufficient to cause measurable differences in system-level metabolism (midday dissolved oxygen concentrations) at all but the lowest test concentration.

Development of an improved attractive lure for the pine shoot beetle, Tomicus piniperda (Coleoptera: Scolytidae).

Abstract  1 The pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Scolytidae), is an exotic pest of pine, Pinus spp., and was first discovered in North America in 1992.

Efficacy of the pheromone (3Z)-lactone and the host kairomone (3Z)-hexenol at detecting early infestation of the emerald ash borer, Agrilus planipennis

The invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp., in its introduced range in North America. Field studies were conducted to quantify the efficacy of traps baited with kairomone and pheromone lures for early detection of A. planipennis infestation. A trapping experiment demonstrated that green traps baited with the kairomone (3Z)‐hexenol detected at least one adult A. planipennis in 55.3% of plots with ‘nil to low’‐density infestations and in 100% of plots with ‘moderate to high’‐density A. planipennis infestations. Mean trap captures increased significantly with increasing infestation density. In terms of the optimal number of traps per plot, when one (3Z)‐hexenol‐baited trap was placed per plot, the trap detected populations in 62% of the plots with ‘low to moderate’‐density infestations through branch sampling. Detectability was increased to 82% when two traps were placed per plot. Finally, addition of female‐produced (3Z)‐lactone pheromone to traps significantly increased detection rates at both the trap and plot level, as compared with traps baited with the host volatile, (3Z)‐hexenol, alone (88 vs. 60%, respectively). Our results are the first to demonstrate the efficacy of baited green sticky traps for detecting low‐density A. planipennis infestations, particularly when the (3Z)‐lactone pheromone is used. This combination is therefore recommended for development of early‐detection protocols against A. planipennis.

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.

Prevalence of Nosema sp. (Microsporidia: Nosematidae) during an outbreak of the jack pine budworm in Ontario.

Microsporidia are believed to play little or no role in outbreaks of the jack pine budworm, Choristoneura pinuspinus Freeman (Lepidoptrera: Tortricidae), because the short duration (2-4 years) of those outbreaks may not permit significant build-up of the pathogen. We conducted the first survey of Nosema sp. (Microsporidia: Nosematidae) over the course of a recent jack pine budworm outbreak in Ontario. Between 2004 and 2010 the outbreak defoliated a cumulative total of 1.78 million ha. Microscopic examination of ~15,000 overwintering larvae collected over 6 years in sites with densities of 3 larvae per branch or more revealed widespread occurrence of Nosema at generally high infection intensities. The pathogen was present in 69.5% of the 518 plots that were monitored. Prevalence of infection was generally low (below 40% in 84% of plots with infected larvae) but reached high levels (80-95%) locally and increased rapidly in most infestations within 1-2 years of onset. We hypothesize that the habit of early-instar larvae to feed on developing male flowers (pollen cones) after spring emergence is critical in allowing rapid build-up of Nosema by increasing efficiency of horizontal transmission (higher density of both infected larvae and egested spores). Nosema infection may contribute to the complexity of jack pine budworm outbreak patterns by affecting egg recruitment and early-instar survival at the stand level in concert with known effects of budworm-induced reductions in pollen cone production on those processes.

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.

Effects of Pheromone Release Rate and Trap Placement on Trapping of Agrilus planipennis (Coleoptera: Buprestidae) in Canada

ABSTRACT The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a devastating insect pest in its introduced range. A trapping system that increases trap catches or detection rates in low-density populations would be beneficial for survey programs. Five trapping experiments were conducted to investigate factors influencing capture rates of male beetles on dark green traps baited with the A. planipennis pheromone, (3Z)-dodecen-12-olide ((3Z)-lactone), plus the green leaf volatile, (3Z)-hexenol. Low doses (0.001–1.0 mg) of (3Z)-lactone + (3Z)-hexenol did not consistently increase captures of male A. planipennis. In other experiments, mean captures of males were significantly higher on traps baited with a moderate dose (3.0 mg/septum) of (3Z)-lactone + (3Z)-hexenol, compared with lower doses (0.001, 0.1, and 1.0 mg) or (3Z)-hexenol alone. Next, we demonstrated that addition of (3Z)-lactone to traps baited with (3Z)-hexenol resulted in significantly greater increases in male captures when pairs of traps were placed on the same tree, than when traps were placed on adjacent trees. Moreover, significantly more A. planipennis were captured on pheromone-baited traps placed in the southern versus northern aspect of the crown. These results highlight the importance of experimental set-up for elucidating lure treatment effects and also suggests the (3Z)-lactone may be more active at close range. Our findings increase our understanding of the pheromone ecology of this species and lend support toward the use of dark green traps baited with 3.0 mg (3Z)-lactone + (3Z)-hexenol deployed in the south aspect of the canopy for detection programs for this insect.