Regional differences in susceptibility to spinosyn insecticides registered for Colorado potato beetle management in Canada.

The Colorado potato beetle (CPB) is the most economically important pest of Canadian potato, and if left uncontrolled, it can completely consume the crop. In the past decade, the control of CPB has relied heavily on systemic insecticides, principally the neonicotinoids thiamethoxam and clothianidin. Resistance to neonicotinoids in CPB has been well documented in the past 2 decades and mechanisms underlying the resistance better understood. In contrast, resistance to other insecticide classes, including spinosyns (spinosad and spinetoram) and anthranillic diamides (chlorantraniliprole and cyantraniliprole), have not been studied to the same degree in CPB. Spinosyns are the only insecticide certified for organic potato growers in Canada and are frequently applied as a mid-season foliar spray by conventional growers when seed treatments with neoniconitoid or diamide experience control breaks. Improved knowledge on resistance to spinosyns in CPB would allow for the development of regional management strategies. A survey of insecticide susceptibility in CPB populations from 6 potato growing regions between 2018 and 2022 observed: 1) spatial and temporal resistance trends; 2) cross-resistance; and 3) evidence of regional differences in susceptibility to spinosyns. The proportion of populations within each province considered resistant to spinosyns was, in descending order: Québec (16%) > Ontario (14%) > Manitoba (13%) > New Brunswick (9%) > Prince Edward Island (2%) > Alberta (0%). There was a significant change in CPB mortality at the diagnostic concentration (DC = LC90) for spinosad and spinetoram in the 6 provinces but only for year 5 relative to the previous 4 years. Moderate cross-resistance was determined between spinosad and spinetoram with the DC mortality for all populations based on a positive and significant correlation (adjusted R2 = 0.3758; P = 1.263e-13). There was also a positive relationship observed between the number of spinosyn applications (years applied at the sampling location) and declining susceptibility to spinosad (R2 = 0.0927; P < 0.002). Cross-resistance was observed between spinosyns and insecticides in the other two classes, the more significant correlation was between spinosad and tetraniliprole (R2 = 0.3025; P < 0.0002). In Québec, the greater spinosad use in organic potato farms led to resistance in those CPB populations, but spinosyn resistance at conventional farms was not related to greater application of neonicotinoids and diamides. Spinosyns remain relatively effective, nevertheless growers should be concerned over the increasing cases of reduced susceptibility in conventional potato farms and resistance where organic production occurs. Resistance management should continue to encourage rotation with products from the other classes in season and between years in order to extend spinosyn use for CPB control.

Investigation of Metabolic Resistance to Soybean Aphid (Aphis glycines Matsumura) Feeding in Soybean Cultivars.

Soybean aphid (Aphis glycines) is a major soybean (Glycine max) herbivore pest in many soybean growing regions. High numbers of aphids on soybean can cause severe reductions in yield. The management of soybean aphids includes monitoring, insecticide applications when required, and the use of resistant cultivars. Soybean aphid-resistant soybean varieties are associated with genes that confer one or more categories of resistance to soybean aphids, including antibiosis (affects survival, growth, and fecundity), antixenosis (affects behaviour such as feeding), and tolerance (plant can withstand greater damage without economic loss). The genetic resistance of soybean to several herbivores has been associated with isoflavonoid phytoalexins; however, this correlation has not been observed in soybean varieties commonly grown in southern Ontario, Canada. Isoflavonoids in the leaves of 18 cultivars in the early growth stage were analyzed by HPLC and the concentration by fresh weight was used to rate the potential resistance to aphids. Greenhouse and growth cabinet trials determined that the cultivars with greater resistance to aphids were Harosoy 63 and OAC Avatar. The most susceptible cultivar was Maple Arrow, whereas Pagoda and Conrad were more tolerant to aphid feeding damage. Overall, there was a low correlation between the number of aphids per leaf, feeding damage, and leaf isoflavonoid levels. Metabolite profiling by high-resolution LC-MS determined that the most resistant cultivar had on average lower levels of certain free amino acids (Met, Tyr, and His) relative to the most susceptible cultivar. This suggests that within the tested cultivars, nutritional quality stimulates aphid feeding more than isoflavonoids negatively affect aphid feeding or growth. These findings provide a better understanding of soybean host plant resistance and suggest ways to improve soybean resistance to aphid feeding through the breeding or metabolic engineering of leaf metabolites.

Soybean (Glycine max L Merr) host-plant defenses and resistance to the two-spotted spider mite (Tetranychus urticae Koch).

In southern Ontario, Canada, the two-spotted spider mite (Tetranychus urticae) is an emerging pest of soybean (Glycine max) due to the increasing incidence of warmer, drier weather conditions. One key strategy to manage soybean pests is breeding resistant cultivars. Resistance to pathogens and herbivores in soybean has been associated with isoflavonoid phytoalexins, a group of specialized metabolites commonly associated with root, leaf and seed tissues. A survey of 18 Ontario soybean cultivars for spider mite resistance included evaluations of antibiosis and tolerance in relation to isoflavonoid and other metabolites detected in the leaves. Ten-day and 4-week trials beginning with early growth stage plants were used to compare survival, growth, fecundity as well as damage to leaves. Two-spotted spider mite (TSSM) counts were correlated with HPLC measurements of isoflavonoid concentration in the leaves and global metabolite profiling by high resolution LC-MS to identify other metabolites unique to the most resistant (R) and susceptible (S) cultivars. Within 10 days, no significant difference (P>0.05) in resistance to TSSM was determined between cultivars, but after 4 weeks, one cultivar, OAC Avatar, was revealed to have the lowest number of adult TSSMs and their eggs. Other cultivars showing partial resistance included OAC Wallace and OAC Lakeview, while Pagoda was the most tolerant to TSSM feeding. A low, positive correlation between isoflavonoid concentrations and TSSM counts and feeding damage indicated these compounds alone do not explain the range of resistance or tolerance observed. In contrast, other metabolite features were significantly different (P<0.05) in R versus S cultivars. In the presence of TSSM, the R cultivars had significantly greater (P<0.05) concentrations of the free amino acids Trp, Val, Thr, Glu, Asp and His relative to S cultivars. Furthermore, the R cultivar metabolites detected are viable targets for more in-depth analysis of their potential roles in TSSM defense.

Proteomic Analyses Detect Higher Expression of C-Type Lectins in Imidacloprid-Resistant Colorado Potato Beetle Leptinotarsa decemlineata Say.

The Colorado potato beetle (CPB) is one of the most adaptable insect pests to both plant toxins and synthetic insecticides. Resistance in CPB is reported for over 50 classes of insecticides, and mechanisms of insecticide-resistance include enhanced detoxification enzymes, ABC transporters and target site mutations. Adaptation to insecticides is also associated with changes in behaviour, energy metabolism and other physiological processes seemingly unrelated to resistance but partially explained through genomic analyses. In the present study, in place of genomics, we applied 2-dimensional (2-D) gel and mass spectrometry to investigate protein differences in abdominal and midgut tissue of insecticide-susceptible (S) and -resistant (R) CPB. The proteomic analyses measured constitutive differences in several proteins, but the highest match was identified as a C-type lectin (CTL), a component of innate immunity in insects. The constitutive expression of the CTL was greater in the multi-resistant (LI) strain, and the same spot was measured in both midgut and abdominal tissue. Exposure to the neonicotinoid insecticide, imidacloprid, increased the CTL spot found in the midgut but not in the abdominal tissue of the laboratory (Lab) strain. No increase in protein levels in the midgut tissue was observed in the LI or a field strain (NB) tolerant to neonicotinoids. With the exception of biopesticides, such as Bacillus thuringiensis (Bt), no previous studies have documented differences in the immune response by CTLs in insects exposed to synthetic insecticides or the fitness costs associated with expression levels of immune-related genes in insecticide-resistant strains. This study demonstrates again how CPB has been successful at adapting to insecticides, plant defenses as well as pathogens.

Resistance to pyridaben in Canadian greenhouse populations of two-spotted spider mites, Tetranychus urticae (Koch).

Two-spotted spider mite (TSSM) Tetranychus urticae (Koch) is an important agricultural pest that causes considerable yield losses to over 150 field and greenhouse crops. Mitochondrial electron transport inhibitors (METI) acaricides are commonly used to control mite species in commercial Canadian greenhouses. Development of resistance to METIs in TSSM populations have been reported worldwide, but not until recently in Canada. The objectives of this study were to: 1) monitor the acaricide-susceptibility in greenhouse TSSM populations, and 2) investigate the resistance to pyridaben, a METI acaricide, in greenhouse resistant and pyridaben-selected (SRS) mite strains. The increased mortality to the pyridaben sub-lethal concentration (LC30) when SRS mites were exposed to piperonyl butoxide (PBO), a general cytochrome P450 monooxygenase inhibitor, and higher P450 activity compared to the greenhouse strain (RS) mites, indicated that P450s may be at least partially responsible for the resistance. The molecular mechanisms of target site insensitivity-mediated resistance in the pyridaben resistant strain of TSSM were investigated by comparing the DNA sequence of NADH dehydrogenase subunits TYKY and PSST, NADH-ubiquinone oxidoreductase chain 1 and 5 (ND1, ND5) and the NADH-ubiquinone oxidoreductase subunit 49 kDa from SRS to the reference strain (SS) and RS. Despite a number of nucleotide substitutions, none correlated with the pyridaben resistance. Understanding the underlying mechanisms of TSSM adaptation to acaricides is an essential part of resistance management strategy in any IPM program. The findings of this study will encourage growers to apply acaricides with different modes of action to reduce the rate at which acaricide resistance will occur in greenhouse TSSM populations.

Beyond 'driving': The relationship between assessment, performance and learning.

OBJECTIVE: Is the statement 'assessment drives learning' a myth? BACKGROUND: Instructors create assessments and students respond to these assessments. Although such responses are often labelled indications of learning, the responses educators observe can also be considered a performance. When responses are aligned with generating stable changes, then assessment drives learning. When responses are not aligned with stable changes, we must consider them to be something else: a performance put on partially or fully for the sake of implying capability rather than actual learning. The alignment between the assessments educators create and the way students respond to these assessments is determined by the actions students take in our curriculum, in preparation for our assessments and after engaging with our assessments. CONCLUSIONS: Not all assessments need to or should support learning, but when we assume all assessments 'drive learning', we endorse the myth that assessment is necessarily a formative aspect of our curricula. When we create assessments that encourage performance activities such as cramming, competing for tutorial airtime and impression management in the clinical setting we drive students to a performance. By thinking about how our students, institutions, curricula and assessments support learning and how well they support performance, we can modify and more fully align our curricular and assessment efforts to support learners in achieving their (and our) desired outcome. So, is the phrase 'assessment drives learning' a myth? This paper will conclude that it often is but we as educators must, through our leadership, move this myth towards a reality.

Host plant defenses of black (Solanum nigrum L.) and red nightshade ( Solanum villosum Mill.) against specialist Solanaceae herbivore Leptinotarsa decemlineata (Say).

Black nightshade (Solanum nigrum, S. nigrum L.) and red nightshade ( Solanum villosum, S. villosum Mill.) are medicinal plants from the Solanaceae family that synthesize glycoalkaloids and other secondary metabolites. To recognize the potential insecticide activity of these compounds, leaf extracts (containing glycoalkaloid and methanol fractions) were tested for enzyme inhibition, antifeedant activity and toxicity. For in-vitro glutathione S-transferase (GST) inhibition activity, we used insecticide-resistant Colorado potato beetle, Leptinotarsa decemlineata ( L. decemlineata; Say) midgut and fat-body homogenate. In-vivo toxicity and the antifeedant activity were performed using larval bioassays. The methanol extracts had greater GST inhibitory activity compared to the glycoalkaloids, as well as greater 2nd instar larvae mortality and antifeedant activity. Furthermore, the green leaf volatile compound, cis-hex-3-enyl acetate, at the concentration of 5 ppm, caused 50% mortality of 2nd instar larvae. Our findings suggest the potential usefulness of S. nigrum and S. villosum extracts to control L. decemlineata.

The Buckwheat Effect: A Biopesticide for Wireworm?

Growing buckwheat (Fagopyrum esculentum Moench. Caryophyllales: Polygonaceae) in rotation with potato and other vegetable crops has been reported to decrease the density of an invasive wireworm species (Agriotes sputator Linnaeus. Coleoptera: Elateridae) in Nova Scotia, Canada. It was predicted that the negative effects on wireworm populations result from phytochemicals by buckwheat that act as deterrents, anti-feedants, or toxins in the roots or when released into the soil. Choice assays were conducted to test the attractiveness of germinating, branching, and flowering buckwheat, red spring wheat (Triticum aestivum Linnaeus. Poales: Poaceae) and island barley (Hordeum vulgare Linnaeus. Poales: Poaceae) to the larvae. Twenty-one day, no choice feeding assays were conducted to determine change in mass and mortality of A. sputator larvae when fed buckwheat or barley. There was no evidence that the wireworms were deterred by buckwheat and the germinating stage of all three crops was the most attractive based on the 24-h choice assays. After the 21-d no choice feeding assays, no differences between hosts were observed; however, wireworm herbivory significantly reduced the growth of barley but not buckwheat. The findings from the no choice feeding assays suggest that buckwheat may produce anti-feedants, but longer term feeding assays and field trials are required to confirm this possibility.

Relationship between Canadian medical school student career interest in emergency medicine and postgraduate training disposition.

BACKGROUND: Canada has two independent routes of emergency medicine (EM) training and certification. This unique situation may encourage medical students with EM career aspirations to apply to family medicine (FM) residencies to subsequently acquire College of Family Physicians of Canada (CFPC) training and certification in EM. We sought answers to the following: 1) Are medical students who indicate EM as their top career choice on medical school entry, and then complete a FM residency, more likely to undertake subsequent CFPC-EM training than other FM residents who did not indicate EM as their top career choice; and 2) What are the characteristics of medical students in four predefined groups, based upon their early interest in EM as a career and ultimate postgraduate training disposition. METHODS: Data were accessed from a survey of medical students in 11 medical school classes from eight Canadian universities and anonymously linked to information from the Canadian Residency Matching Service between 2006 and 2009. RESULTS: Of 1036 participants, 63 (6.1%) named EM as their top career choice on medical school entry. Of these, 10 ultimately matched to a Royal College of Physicians and Surgeons of Canada (RCPSC) EM residency program, and 24 matched to a FM residency program, nine of whom went on to do a one-year CFPC-EM residency program in contrast to 57 of the remaining 356 students matching to FM residency programs who did not indicate EM was their top career choice (37.5% vs 16.0%, p=0.007). Statistically significant attitudinal differences related to the presence or absence of EM career interest on medical school entry were found. CONCLUSION: Considering those who complete CFPC-EM training, a greater proportion indicate on admission to medical school that EM is their top career choice compared to those who do not. Moreover, students with an early career interest in EM are similar for several attitudinal factors independent of their ultimate postgraduate training disposition. Given the current issues and challenges facing FM and EM, these findings have implications that merit consideration by both the CFPC and the RCPSC.

Plant growth regulator-mediated anti-herbivore responses of cabbage (Brassica oleracea) against cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae).

Plant elicitors can be biological or chemical-derived stimulators of jasmonic acid (JA) or salicylic acid (SA) pathways shown to prime the defenses in many crops. Examples of chemical elicitors of the JA and SA pathways include methyl-jasmonate and 1,2,3-benzothiadiazole-7-carbothioate (BTH or the commercial plant activator Actigard 50WG, respectively). The use of specific elicitors has been observed to affect the normal interaction between JA and SA pathways causing one to be upregulated and the other to be suppressed, often, but not always, at the expense of the plant's herbivore or pathogen defenses. The objective of this study was to determine whether insects feeding on Brassica crops might be negatively affected by SA inducible defenses combined with an inhibitor of detoxification and anti-oxidant enzymes that regulate the insect response to the plant's defenses. The relative growth rate of cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae) fed induced cabbage Brassica oleraceae leaves with the inhibitor, quercetin, was significantly less than those fed control cabbage with and without the inhibitor. The reduced growth was related to the reduction of glutathione S-transferases (GSTs) by the combination of quercetin and increased levels of indole glucosinolates in the cabbage treated with BTH at 2.6× the recommended application rate. These findings may offer a novel combination of elicitor and synergist that can provide protection from plant disease and herbivores in cabbage and other Brassica crops.

Saprotrophic proteomes of biotypes of the witches' broom pathogen Moniliophthora perniciosa.

Nine geographically diverse Moniliophthora perniciosa (witches' broom disease pathogen) isolates were cultured in vitro. They included six C-biotypes differing in virulence on cacao (Theobroma cacao), two S-biotypes (solanaceous hosts), and an L-biotype (liana hosts). Mycelial growth rates and morphologies differed considerably, but no characters were observed to correlate with virulence or biotype. In plant inoculations using basidiospores, one C-biotype caused symptoms on tomato (an S-biotype host), adding to evidence of limited host adaptation in these biotypes. Mycelial proteomes were analysed by two-dimensional gel electrophoresis (2-DE), and 619 gel spots were indexed on all replicate gels of at least one strain. Multivariate analysis of gel spots discriminated the L-biotype, but not the S-biotypes, from the remaining strains. The proteomic similarity of the S- and C-biotypes is consistent with their reported lack of phylogenetic distinction. Sequences from tandem mass spectrometry of tryptic peptides from major 2-DE spots were matched with Moniliophthora genome and transcript sequences on NCBI and WBD Transcriptome Atlas databases. Protein-spot identifications indicated that M. perniciosa saprotrophic mycelial proteomes expressed functions potentially connected with a 'virulence life-style', including peroxiredoxin, heat-shock proteins, nitrilase, formate dehydrogenase, a prominent complement of aldo-keto reductases, mannitol-1-phosphate dehydrogenase, and central metabolism enzymes with proposed pathogenesis functions.

Predicting future biomass yield in Miscanthus using the carbohydrate metabolic profile as a biomarker.

In perennial energy crop breeding programmes, it can take several years before a mature yield is reached when potential new varieties can be scored. Modern plant breeding technologies have focussed on molecular markers, but for many crop species, this technology is unavailable. Therefore, prematurity predictors of harvestable yield would accelerate the release of new varieties. Metabolic biomarkers are routinely used in medicine, but they have been largely overlooked as predictive tools in plant science. We aimed to identify biomarkers of productivity in the bioenergy crop, Miscanthus, that could be used prognostically to predict future yields. This study identified a metabolic profile reflecting productivity in Miscanthus by correlating the summer carbohydrate composition of multiple genotypes with final yield 6 months later. Consistent and strong, significant correlations were observed between carbohydrate metrics and biomass traits at two separate field sites over 2 years. Machine-learning feature selection was used to optimize carbohydrate metrics for support vector regression models, which were able to predict interyear biomass traits with a correlation (R) of >0.67 between predicted and actual values. To identify a causal basis for the relationships between the glycome profile and biomass, a 13C-labelling experiment compared carbohydrate partitioning between high- and low-yielding genotypes. A lower yielding and slower growing genotype partitioned a greater percentage of the 13C pulse into starch compared to a faster growing genotype where a greater percentage was located in the structural biomass. These results supported a link between plant performance and carbon flow through two rival pathways (starch vs. sucrose), with higher yielding plants exhibiting greater partitioning into structural biomass, via sucrose metabolism, rather than starch. Our results demonstrate that the plant metabolome can be used prognostically to anticipate future yields and this is a method that could be used to accelerate selection in perennial energy crop breeding programmes.

Overexpression of a cytochrome P450 and a UDP-glycosyltransferase is associated with imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata.

Current control of insect pests relies on chemical insecticides, however, insecticide resistance development by pests is a growing concern in pest management. The main mechanisms for insecticide resistance typically involve elevated activity of detoxifying enzymes and xenobiotic transporters that break-down and excrete insecticide molecules. In this study, we investigated the molecular mechanisms of imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), an insect pest notorious for its capacity to develop insecticide resistance rapidly. We compared the transcriptome profiles of imidacloprid-resistant and sensitive beetle strains and identified 102 differentially expressed transcripts encoding detoxifying enzymes and xenobiotic transporters. Of these, 74 were up-regulated and 28 were down-regulated in the resistant strain. We then used RNA interference to knock down the transcript levels of seven up-regulated genes in the resistant beetles. Ingestion of double-stranded RNA successfully knocked down the expression of the genes for three cytochrome P450s (CYP6BQ15, CYP4Q3 and CYP4Q7), one ATP binding cassette (ABC) transporter (ABC-G), one esterase (EST1), and two UDP-glycosyltransferases (UGT1 and UGT2). Further, we demonstrated that silencing of CYP4Q3 and UGT2 significantly increased susceptibility of resistant beetles to imidacloprid, indicating that overexpression of these two genes contributes to imidacloprid resistance in this resistant strain.

Laboratory studies of insecticide efficacy and resistance in Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) populations from British Columbia, Canada.

BACKGROUND: Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura), control can be improved with better knowledge of insecticide efficacy, timing of sprays and rotations with registered products during the crop year. An efficacy bioassay was applied to study the dose response of adult laboratory-reared SWD collected from a cherry orchard in British Columbia (BC), Canada, to 11 insecticides. RESULTS: Age- and sex-specific toxicities with the most effective insecticide, malathion, determined that older male SWD were significantly more susceptible than females. The selection for polygenic resistance to malathion using repeated exposure to sublethal concentrations with both the original and an additional blueberry-collected population of laboratory-reared SWD determined no significant difference in susceptibility after 30 generations. CONCLUSION: Possible reasons reported in D. melanogaster studies where resistance did not occur after insecticide selection included avoidance and associated microbial complexes. The low level of malathion resistance observed in the selected SWD populations and a field-collected population is useful information in the development of insecticide resistance management programmes. © 2016 Her Majesty the Queen in Right of Canada Pest Management Science © 2016 Society of Chemical Industry.

Application of 1D and 2D MFR reactor technology for the isolation of insecticidal and anti-microbial properties from pyrolysis bio-oils.

Valuable chemicals can be separated from agricultural residues by chemical or thermochemical processes. The application of pyrolysis has already been demonstrated as an efficient means to produce a liquid with a high concentration of desired product. The objective of this study was to apply an insect and microorganism bioassay-guided approach to separate and isolate pesticidal compounds from bio-oil produced through biomass pyrolysis. Tobacco leaf (Nicotianata bacum), tomato plant (Solanum lycopersicum), and spent coffee (Coffea arabica) grounds were pyrolyzed at 10°C/min from ambient to 565°C using the mechanically fluidized reactor (MFR). With one-dimensional (1D) MFR pyrolysis, the composition of the product vapors varied as the reactor temperature was raised allowing for the selection of the temperature range that corresponds to vapors with a high concentration of pesticidal properties. Further product separation was performed in a fractional condensation train, or 2D MFR pyrolysis, thus allowing for the separation of vapor components according to their condensation temperature. The 300-400°C tobacco and tomato bio-oil cuts from the 1D MFR showed the highest insecticidal and anti-microbial activity compared to the other bio-oil cuts. The 300-350 and 350-400°C bio-oil cuts produced by 2D MFR had the highest insecticidal activity when the bio-oil was collected from the 210°C condenser. The tobacco and tomato bio-oil had similar insecticidal activity (LC50 of 2.1 and 2.2 mg/mL) when the bio-oil was collected in the 210°C condenser from the 300-350°C reactor temperature gases. The 2D MFR does concentrate the pesticidal products compared to the 1D MFR and thus can reduce the need for further separation steps such as solvent extraction.

Conifer flavonoid compounds inhibit detoxification enzymes and synergize insecticides.

Detoxification by glutathione S-transferases (GSTs) and esterases are important mechanisms associated with insecticide resistance. Discovery of novel GST and esterase inhibitors from phytochemicals could provide potential new insecticide synergists. Conifer tree species contain flavonoids, such as taxifolin, that inhibit in vitro GST activity. The objectives were to test the relative effectiveness of taxifolin as an enzyme inhibitor and as an insecticide synergist in combination with the organophosphorous insecticide, Guthion (50% azinphos-methyl), and the botanical insecticide, pyrethrum, using an insecticide-resistant Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) strain. Both taxifolin and its isomer, quercetin, increased the mortality of 1(st) instar CPB larvae after 48h when combined with Guthion, but not pyrethrum. Taxifolin had greater in vitro esterase inhibition compared with the commonly used esterase inhibitor, S, S, S-tributyl phosphorotrithioate (DEF). An in vivo esterase and GST inhibition effect after ingestion of taxifolin was measured, however DEF caused a greater suppression of esterase activity. This study demonstrated that flavonoid compounds have both in vitro and in vivo esterase inhibition, which is likely responsible for the insecticide synergism observed in insecticide-resistant CPB.

Susceptibility in field populations of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in Ontario and Quebec apple orchards to a selection of insecticides.

BACKGROUND: Codling moth is a major pest of pome fruit worldwide. Insecticide resistance has become a widespread pest management issue. However, the current status of insecticide resistance in Ontario and Quebec codling moth populations is unknown. RESULTS: Codling moth populations were collected from 27 orchards in Ontario and Quebec from 2008 to 2010. A series of laboratory bioassays were performed to establish baseline susceptibility of adults and larvae to azinphos-methyl, thiacloprid, chlorantraniliprole and methoxyfenozide. Adult codling moth percentage mortality ranged from 22 to 97% and from 21 to 85% when exposed to topical bioassays using azinphos-methyl and thiacloprid respectively. Azinphos-methyl LC50 values from three selected orchards were ca fivefold greater than those from an insecticide-susceptible population. Neonate larva percentage mortality ranged from 5 to 50%, from 15 to 65%, from 90 to 100% and from 10 to 40% when exposed to diet bioassays using azinphos-methyl, thiacloprid, chlorantraniliprole and methoxyfenozide respectively. CONCLUSION: Based on the response of the field-collected populations, resistance development to some registered insecticides was evident in some Ontario and Quebec populations. With the present status of insecticide resistance documented in these regions, modifications to codling moth management strategies should be initiated before changes in field efficacy occur.

Insecticide resistance and cross-resistance development in Colorado potato beetle Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) populations in Canada 2008-2011.

BACKGROUND: A survey of insecticide resistance in over 150 Canadian populations of Colorado potato beetle was completed between 2008 and 2011. Three neonicotinoid and two anthranilic diamide insecticides were tested at a discriminating concentration (DC) with second-instar larvae in a leaf-disc bioassay. RESULTS: The mean mortality for the imidacloprid (Admire) DC was 46-67% between 2008 and 2011 respectively. Over the 4 years, 10-46% and 26-40% of the populations were classified as resistant or showed reduced susceptibility to imidacloprid. The mean mortality for thiamethoxam (Actara) and clothianidin (Poncho/Titan) ranged from 56-76% in 2008 to 81-84% in 2010 for each insecticide respectively, indicating continuous susceptibility to clothianidin but reduced susceptibility to thiamethoxam. In 2008 and 2009, susceptibility to chlorantraniliprole (Coragen) was observed in 85% of populations. Similarly, cyantraniliprole (Cyazypyr) affected 93% of the 2009 and 74% of the 2010 populations. There was a significant (P < 0.05) and high positive correlation (R = 0.4-0.84) between the three neonicotinoids, indicating the potential for cross-resistance. CONCLUSIONS: The trend observed in decreasing susceptibility for thiamethoxam and clothianidin will continue unless resistance management practices are followed.

Inhibition of insect glutathione S-transferase (GST) by conifer extracts.

Insecticide synergists biochemically inhibit insect metabolic enzyme activity and are used both to increase the effectiveness of insecticides and as a diagnostic tool for resistance mechanisms. Considerable attention has been focused on identifying new synergists from phytochemicals with recognized biological activities, specifically enzyme inhibition. Jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP.), balsam fir (Abies balsamea (L.) Mill.), and tamarack larch (Larix laricina (Du Roi) Koch) have been used by native Canadians as traditional medicine, specifically for the anti-inflammatory and antioxidant properties based on enzyme inhibitory activity. To identify the potential allelochemicals with synergistic activity, ethanol crude extracts and methanol/water fractions were separated by Sephadex LH-20 chromatographic column and tested for in vitro glutathione S-transferase (GST) inhibition activity using insecticide-resistant Colorado potato beetle, Leptinotarsa decemlineata (Say) midgut and fat-body homogenate. The fractions showing similar activity were combined and analyzed by ultra pressure liquid chromatography-mass spectrometry. A lignan, (+)-lariciresinol 9'-p-coumarate, was identified from P. mariana cone extracts, and L. laricina and A. balsamea bark extracts. A flavonoid, taxifolin, was identified from P. mariana and P. banksiana cone extracts and L. laricina bark extracts. Both compounds inhibit GST activity with taxifolin showing greater activity compared to (+)-lariciresinol 9'-p-coumarate and the standard GST inhibitor, diethyl maleate. The results suggested that these compounds can be considered as potential new insecticide synergists.

Insecticidal activity of bio-oil from the pyrolysis of straw from Brassica spp.

Agricultural crop residues can be converted through thermochemical pyrolysis to bio-oil, a sustainable source of biofuel and biochemicals. The pyrolysis bio-oil is known to contain many chemicals, some of which have insecticidal activity and can be a potential source of value-added pest control products. Brassicacae crops, cabbage, broccoli, and mustards, contain glucosinolates and isocyanates, compounds with recognized anti-herbivore activity. In Canada, canola Brassica napus straw is available from over 6 000 000 ha and mustard Brassica carinata and Brassica juncea straw is available from 200 000 ha. The straw can be converted by microbial lignocellulosic enzymes as a substrate for bioethanol production but can also be converted to bio-oil by thermochemical means. Straw from all three species was pyrolyzed, and the insecticidal components in the bio-oil were isolated by bioassay-guided solvent fractionation. Of particular interest were the mustard straw bio-oil aqueous fractions with insecticidal and feeding repellent activity to Colorado potato beetle larvae. Aqueous fractions further analyzed for active compounds were found not to contain many of the undesirable phenol compounds, which were previously found in other bio-oils seen in the dichloromethane (DCM) and ethyl acetate (EA) solvent phases of the present study. Identified within the most polar fractions were hexadecanoic and octadecanoic fatty acids, indicating that separation of these compounds during bio-oil production may provide a source of effective insecticidal compounds.