Steven J. Harte - Academia.edu (original) (raw)

Papers by Steven J. Harte

Frontiers in Forests and Global Change

Introduction and main objectiveBursaphelenchus xylophilus, commonly known as pine wood nematode (... more Introduction and main objectiveBursaphelenchus xylophilus, commonly known as pine wood nematode (PWN), is considered one of the greatest threats to European and Asian pines. Regarding its management, most efforts have been directed toward control measures for the major vector (Monochamus spp.) and screening for genetic resistance in its hosts. However, an integrated pest management strategy which also implements pinewood nematode control is currently lacking. The aim of this study was to evaluate the nematicidal effect of two Beauveria species, a genus well known for its entomopathogenic activity.Summary methodologyFor this purpose, in vitro antagonism tests of fungi (Beauveria bassiana and B. pseudobassiana) and the mycotoxin beauvericin (C45H57N3O9) on B. xylophilus populations were conducted. Finally, the production of beauvericin in B. bassiana and B. pseudobassiana strains was quantified by high-performance liquid chromatography - mass spectrometry (HPLC-MS).Results and discuss...

Scientific Reports , 2024

Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently ... more Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently become established in sub-Saharan Africa and Southeast Asia. Current FAW control is almost entirely dependent on synthetic pesticides. Biopesticides offer a more sustainable alternative but have limitations. For example, pyrethrum is an effective botanical insecticide with low mammalian toxicity but is highly UV labile, resulting in a rapid loss of efficacy in the field. Beauveria bassiana is an entomopathogenic fungus that is more persistent, but there is a time lag of several days before it causes insect mortality and leads to effective control. The combination of these biopesticides could mitigate their drawbacks for FAW control. Here we evaluated the efficacy of pyrethrum and B. bassiana as individual treatments and in combination against 3 rd instar FAW. Four different combinations of these two biopesticides were tested, resulting in an antagonistic relationship at the lowest concentrations of B. bassiana and pyrethrum (1 × 10 4 conidia mL −1 with 25 ppm) and an additive effect for the other 3 combined treatments (1 × 10 4 conidia mL −1 with 100 ppm and 1 × 10 5 conidia mL −1 with 25 ppm and 100 ppm pyrethrum). Additionally, a delay in efficacy from B. bassiana was observed when combined with pyrethrum as well as a general inhibition of growth on agar plates. These results appear to show that this particular combination of biopesticides is not universally beneficial or detrimental to pest control strategies and is dependent on the doses of each biopesticide applied. However, the additive effect shown here at specific concentrations does indicate that combining biopesticides could help overcome the challenges of persistence seen in botanical pesticides and the slow establishment of EPF, with the potential to improve effectiveness of biopesticides for IPM.

Insects

The worldwide invasive insect pest, Drosophila suzukii Matsumura (spotted-wing Drosophila), lays ... more The worldwide invasive insect pest, Drosophila suzukii Matsumura (spotted-wing Drosophila), lays eggs in soft and stone fruit before harvest. Hatched larvae cause fruit collapse and significant economic losses. Current control methods rely primarily on foliar insecticide applications, which are not sustainable long-term solutions due to regulatory restrictions and the risk of insecticide resistance developing. We showed before that D. suzukii were deterred from laying eggs on artificial media previously visited by its sister species—Drosophila melanogaster. In the current study, laboratory choice test experiments were conducted to identify which D. melanogaster life stage (eggs, larvae, or adult) deterred D. suzukii oviposition. We demonstrated that the presence of live D. melanogaster larvae on the egg-laying media consistently deterred D. suzukii oviposition. Drosophila melanogaster cuticular hydrocarbons (CHCs) were examined as candidate for the oviposition deterrent. CHCs of lar...

Journal of Chemical Ecology, 2021

Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a tropical mirid bug used as a biocontrol ... more Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a tropical mirid bug used as a biocontrol agent in protected crops, including tomatoes. Although N. tenuis predates important insect pests, especially whitefly, it also causes damage by feeding on tomato plants when prey populations decline, resulting in significant economic losses for growers. The pest is now established in some all-year-round tomato crops in Europe and control measures involve the application of pesticides which are incompatible with current IPM programs. As part of future IPM strategies, the pheromone of N. tenuis was investigated. Volatile collections were made from groups and individuals of mated and unmated, females and males. In analyses of these collections by gas chromatography coupled with electroantennographic (EAG) recording from antennae of male bugs, two EAG-active components were detected and identified as 1-octanol and octyl hexanoate. Unlike other mirids, both male and female N. tenuis produced ...

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied O. rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. There were anecdotal reports that the commercial lures containing this compound were not attractive to CRB-G and the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults failed to show any male- or female-specific compounds as candidate pheromone components. Only after five months ...

The asparagus beetle, Crioceris asparagi L. (Coleoptera; Chrysomelidae) has become a widespread p... more The asparagus beetle, Crioceris asparagi L. (Coleoptera; Chrysomelidae) has become a widespread pest of asparagus, Asparagus officinalis (asparagus). There are no known attractants for C. asparagi and much of its biology is unknown. Volatiles were collected from individual beetles and a candidate pheromone component was detected in collections from some individuals of the first generation but not the second. This compound elicited an electroantennographic response from C. asparagi and the mass spectrum indicated it is a 19-carbon hydrocarbon with four double bonds. Complete structural elucidation and synthesis are in progress.

Journal of Chemical Ecology, 2021

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied Oryctes rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. Following reports from growers that commercial lures containing this compound were not attractive to CRB-G, the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults from the Solomon Islands failed to show any male- or female-specific compounds as candidate pheromone components...

Journal of Chemical Ecology, 2021

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied Oryctes rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. Following reports from growers that commercial lures containing this compound were not attractive to CRB-G, the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults from the Solomon Islands failed to show any male- or female-specific compounds as candidate pheromone components...

Plants, 2020

Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest ... more Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest management, but these are not always a direct replacement. Botanical insecticides, for example, have rapid knockdown but are highly labile and while biological pesticides are more persistent, they are slow acting. To mitigate these shortcomings, we combined the entomopathogenic fungus (EPF) Metarhizium anisopliae with pyrethrum and evaluated their efficacy against the bean aphid, Aphis fabae. To ascertain higher trophic effects, we presented these treatments to the parasitoid, Aphidius colemani, on an aphid infested plant in a Y-tube olfactometer and measured their preferences. Aphid mortality was significantly higher than controls when exposed to EPF or pyrethrum but was greater still when exposed to a combination of both treatments, indicating an additive effect. This highlights the potential for applications of pyrethrum at lower doses, or the use of less refined products with lower p...

Journal of Chemical Ecology

The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-desc... more The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-described species that induces galls on canola, Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae). Identification of the sex pheromone of C. brassicola is essential to developing monitoring tools to elucidate the geographic range and hosts of this new pest, and the extent to which it threatens the $30 billion Canadian canola industry. The aim of this study was to identify and synthesize the female-produced sex pheromone of C. brassicola and demonstrate its effectiveness in attracting males to traps in the field. Two peaks were identified through GC-EAG analysis of female-produced volatiles which elicited electrophysiological responses in male antennae. These peaks were initially characterized through GC–MS and synthesis as 2,7-diacetoxynonane (major component) and 2-acetoxynonane (minor component), and the racemic compounds elicited EAG responses in male antennae. All four st...

www.mdpi.com/journal/plants, 2020

Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest ... more Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest management, but these are not always a direct replacement. Botanical insecticides, for example, have rapid knockdown but are highly labile and while biological pesticides are more persistent, they are slow acting. To mitigate these shortcomings, we combined the entomopathogenic fungus (EPF) Metarhizium anisopliae with pyrethrum and evaluated their efficacy against the bean aphid, Aphis fabae. To ascertain higher trophic effects, we presented these treatments to the parasitoid, Aphidius colemani, on an aphid infested plant in a Y-tube olfactometer and measured their preferences. Aphid mortality was significantly higher than controls when exposed to EPF or pyrethrum but was greater still when exposed to a combination of both treatments, indicating an additive effect. This highlights the potential for applications of pyrethrum at lower doses, or the use of less refined products with lower production costs to achieve control. While parasitoids were deterred by aphid infested plants treated with EPF, no preference was observed with the combination pesticide, which provides insight into the importance that both application technique and timing may play in the success of this new technology. These results indicate the potential for biorational pesticides that combine botanicals with EPF.

Frontiers in Forests and Global Change

Introduction and main objectiveBursaphelenchus xylophilus, commonly known as pine wood nematode (... more Introduction and main objectiveBursaphelenchus xylophilus, commonly known as pine wood nematode (PWN), is considered one of the greatest threats to European and Asian pines. Regarding its management, most efforts have been directed toward control measures for the major vector (Monochamus spp.) and screening for genetic resistance in its hosts. However, an integrated pest management strategy which also implements pinewood nematode control is currently lacking. The aim of this study was to evaluate the nematicidal effect of two Beauveria species, a genus well known for its entomopathogenic activity.Summary methodologyFor this purpose, in vitro antagonism tests of fungi (Beauveria bassiana and B. pseudobassiana) and the mycotoxin beauvericin (C45H57N3O9) on B. xylophilus populations were conducted. Finally, the production of beauvericin in B. bassiana and B. pseudobassiana strains was quantified by high-performance liquid chromatography - mass spectrometry (HPLC-MS).Results and discuss...

Scientific Reports , 2024

Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently ... more Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently become established in sub-Saharan Africa and Southeast Asia. Current FAW control is almost entirely dependent on synthetic pesticides. Biopesticides offer a more sustainable alternative but have limitations. For example, pyrethrum is an effective botanical insecticide with low mammalian toxicity but is highly UV labile, resulting in a rapid loss of efficacy in the field. Beauveria bassiana is an entomopathogenic fungus that is more persistent, but there is a time lag of several days before it causes insect mortality and leads to effective control. The combination of these biopesticides could mitigate their drawbacks for FAW control. Here we evaluated the efficacy of pyrethrum and B. bassiana as individual treatments and in combination against 3 rd instar FAW. Four different combinations of these two biopesticides were tested, resulting in an antagonistic relationship at the lowest concentrations of B. bassiana and pyrethrum (1 × 10 4 conidia mL −1 with 25 ppm) and an additive effect for the other 3 combined treatments (1 × 10 4 conidia mL −1 with 100 ppm and 1 × 10 5 conidia mL −1 with 25 ppm and 100 ppm pyrethrum). Additionally, a delay in efficacy from B. bassiana was observed when combined with pyrethrum as well as a general inhibition of growth on agar plates. These results appear to show that this particular combination of biopesticides is not universally beneficial or detrimental to pest control strategies and is dependent on the doses of each biopesticide applied. However, the additive effect shown here at specific concentrations does indicate that combining biopesticides could help overcome the challenges of persistence seen in botanical pesticides and the slow establishment of EPF, with the potential to improve effectiveness of biopesticides for IPM.

Insects

The worldwide invasive insect pest, Drosophila suzukii Matsumura (spotted-wing Drosophila), lays ... more The worldwide invasive insect pest, Drosophila suzukii Matsumura (spotted-wing Drosophila), lays eggs in soft and stone fruit before harvest. Hatched larvae cause fruit collapse and significant economic losses. Current control methods rely primarily on foliar insecticide applications, which are not sustainable long-term solutions due to regulatory restrictions and the risk of insecticide resistance developing. We showed before that D. suzukii were deterred from laying eggs on artificial media previously visited by its sister species—Drosophila melanogaster. In the current study, laboratory choice test experiments were conducted to identify which D. melanogaster life stage (eggs, larvae, or adult) deterred D. suzukii oviposition. We demonstrated that the presence of live D. melanogaster larvae on the egg-laying media consistently deterred D. suzukii oviposition. Drosophila melanogaster cuticular hydrocarbons (CHCs) were examined as candidate for the oviposition deterrent. CHCs of lar...

Journal of Chemical Ecology, 2021

Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a tropical mirid bug used as a biocontrol ... more Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a tropical mirid bug used as a biocontrol agent in protected crops, including tomatoes. Although N. tenuis predates important insect pests, especially whitefly, it also causes damage by feeding on tomato plants when prey populations decline, resulting in significant economic losses for growers. The pest is now established in some all-year-round tomato crops in Europe and control measures involve the application of pesticides which are incompatible with current IPM programs. As part of future IPM strategies, the pheromone of N. tenuis was investigated. Volatile collections were made from groups and individuals of mated and unmated, females and males. In analyses of these collections by gas chromatography coupled with electroantennographic (EAG) recording from antennae of male bugs, two EAG-active components were detected and identified as 1-octanol and octyl hexanoate. Unlike other mirids, both male and female N. tenuis produced ...

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied O. rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. There were anecdotal reports that the commercial lures containing this compound were not attractive to CRB-G and the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults failed to show any male- or female-specific compounds as candidate pheromone components. Only after five months ...

The asparagus beetle, Crioceris asparagi L. (Coleoptera; Chrysomelidae) has become a widespread p... more The asparagus beetle, Crioceris asparagi L. (Coleoptera; Chrysomelidae) has become a widespread pest of asparagus, Asparagus officinalis (asparagus). There are no known attractants for C. asparagi and much of its biology is unknown. Volatiles were collected from individual beetles and a candidate pheromone component was detected in collections from some individuals of the first generation but not the second. This compound elicited an electroantennographic response from C. asparagi and the mass spectrum indicated it is a 19-carbon hydrocarbon with four double bonds. Complete structural elucidation and synthesis are in progress.

Journal of Chemical Ecology, 2021

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied Oryctes rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. Following reports from growers that commercial lures containing this compound were not attractive to CRB-G, the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults from the Solomon Islands failed to show any male- or female-specific compounds as candidate pheromone components...

Journal of Chemical Ecology, 2021

The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dyna... more The coconut rhinoceros beetle, Oryctes rhinoceros (Linnaeus 1758) (Coleoptera: Scarabaeidae: Dynastinae) (CRB), is endemic to tropical Asia where it damages both coconut and oil palm. A new invasion by CRB occurred on Guam in 2007 and eradication attempts failed using commonly applied Oryctes rhinoceros nudivirus (OrNV) isolates. This and subsequent invasive outbreaks were found to have been caused by a previously unrecognized haplotype, CRB-G, which appeared to be tolerant to OrNV. The male-produced aggregation pheromone of the endemic, susceptible strain of O. rhinoceros (CRB-S) was previously identified as ethyl 4-methyloctanoate. Following reports from growers that commercial lures containing this compound were not attractive to CRB-G, the aim of this work was to identify the pheromone of CRB-G. Initial collections of volatiles from virgin male and female CRB-G adults from the Solomon Islands failed to show any male- or female-specific compounds as candidate pheromone components...

Plants, 2020

Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest ... more Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest management, but these are not always a direct replacement. Botanical insecticides, for example, have rapid knockdown but are highly labile and while biological pesticides are more persistent, they are slow acting. To mitigate these shortcomings, we combined the entomopathogenic fungus (EPF) Metarhizium anisopliae with pyrethrum and evaluated their efficacy against the bean aphid, Aphis fabae. To ascertain higher trophic effects, we presented these treatments to the parasitoid, Aphidius colemani, on an aphid infested plant in a Y-tube olfactometer and measured their preferences. Aphid mortality was significantly higher than controls when exposed to EPF or pyrethrum but was greater still when exposed to a combination of both treatments, indicating an additive effect. This highlights the potential for applications of pyrethrum at lower doses, or the use of less refined products with lower p...

Journal of Chemical Ecology

The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-desc... more The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-described species that induces galls on canola, Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae). Identification of the sex pheromone of C. brassicola is essential to developing monitoring tools to elucidate the geographic range and hosts of this new pest, and the extent to which it threatens the $30 billion Canadian canola industry. The aim of this study was to identify and synthesize the female-produced sex pheromone of C. brassicola and demonstrate its effectiveness in attracting males to traps in the field. Two peaks were identified through GC-EAG analysis of female-produced volatiles which elicited electrophysiological responses in male antennae. These peaks were initially characterized through GC–MS and synthesis as 2,7-diacetoxynonane (major component) and 2-acetoxynonane (minor component), and the racemic compounds elicited EAG responses in male antennae. All four st...

www.mdpi.com/journal/plants, 2020

Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest ... more Sustainable agricultural intensification employs alternatives to synthetic insecticides for pest management, but these are not always a direct replacement. Botanical insecticides, for example, have rapid knockdown but are highly labile and while biological pesticides are more persistent, they are slow acting. To mitigate these shortcomings, we combined the entomopathogenic fungus (EPF) Metarhizium anisopliae with pyrethrum and evaluated their efficacy against the bean aphid, Aphis fabae. To ascertain higher trophic effects, we presented these treatments to the parasitoid, Aphidius colemani, on an aphid infested plant in a Y-tube olfactometer and measured their preferences. Aphid mortality was significantly higher than controls when exposed to EPF or pyrethrum but was greater still when exposed to a combination of both treatments, indicating an additive effect. This highlights the potential for applications of pyrethrum at lower doses, or the use of less refined products with lower production costs to achieve control. While parasitoids were deterred by aphid infested plants treated with EPF, no preference was observed with the combination pesticide, which provides insight into the importance that both application technique and timing may play in the success of this new technology. These results indicate the potential for biorational pesticides that combine botanicals with EPF.