Twelve selected cultivated or wild solanaceae (Solanum dulcamara, Solanum nigrum, Solanum villosu... more Twelve selected cultivated or wild solanaceae (Solanum dulcamara, Solanum nigrum, Solanum villosum, Solanum lycopersicum, Solanum muricatum, Solanum melongena, Datura innoxia, Datura metel, Physalis spp., Capsicum annuum, Nicotiana alata, and Petunia spp.) (all species Solanales: Solanaceae) were tested as potential alternative host plants against Solanum tuberosum for a local population of the Colorado potato beetle Leptinotarsa decemlineata Say (CPB) in Estonia. Some CPB populations in America and southern Europe accept most of these plants. However, geographically isolated populations of beetles can differ in their acceptance of new host plants. Migrants from the southern Europe supplement Estonian beetle population regularly, so individuals may differ in their host plant preferences. S. melongena and S. dulcamara were well accepted by the beetles, Lycopersicum spp. (Solanales: Solanaceae) and N. alata were intermediate, and S. villosum and S. nigrum were least accepted. The beet...
ABSTRACT Oilseed rape (Brassica napus) is a valuable crop, attacked by several insect pests, of w... more ABSTRACT Oilseed rape (Brassica napus) is a valuable crop, attacked by several insect pests, of which the pollen beetle (Meligethes aeneus) is one of the most widespread and important in Europe. The relative attractiveness for the pollen beetle of Brassica nigra, Eruca sativa and Raphanus sativus was compared with that of spring oilseed rape, to assess the potential of these plant species as trap crops for the pest. At early growth stages, B. nigra and R. sativus were more attractive to over-wintered adult pollen beetles than B. napus. At the bud and flowering stages, B. nigra was the most attractive while E. sativa was the least attractive. At flowering, B. nigra was more attractive for oviposition than the other species. Thus, of the species tested, B. nigra has the most potential as a prospective trap crop to protect spring oilseed rape before flowering when it is at its most vulnerable developmental phase, due to its faster development and its acceptability both for feeding and oviposition to overwintered pollen beetle adults. Raphanus sativus was accepted both for feeding and oviposition, but pollen beetle larvae failed to develop in its flowers; it therefore has the potential for use as a dead-end crop. At the end of the growing season, both E. sativa and R. sativus, as late-flowering species, attracted the new generation of pollen beetles and thereby have potential to extend the effectiveness of a trap-cropping system at this time.
Supercooling ability and cold hardiness in the horseradish flea beetle Phyllotreta armoracia (Koc... more Supercooling ability and cold hardiness in the horseradish flea beetle Phyllotreta armoracia (Koch)(Coleoptera: Chrysomelidae: Alticinae) was investigated. Mean supercooling points (SCP) varied from− 10.1 to− 23.9 C depending on the season: SCP ...
Reviewed are the results of treatments carried out in the Institute of Agricultural and Environme... more Reviewed are the results of treatments carried out in the Institute of Agricultural and Environmental Sciences of treatments with natural insecticidal substances on the development and physiological state of insects, using neurotoxical plant extracts (pyrethrins), plant extracts possessing several modes of action (neem) and an Insect Growth Regulator (extract of Ledum palustre possessing properties of juvenile hormone). Physiological changes evoked with treatments were monitored by means of complex methods including a constant volume respirometer, infrared actograph, infrared gas analyzer (IRGA),and a microcalorimeter. Diapausing lepidopterous pupae (Pieris brassicae, Mamestra brassicae) exhibited discontinuous gas exchange cycles (DGCs). After treatments of the pupae of P. brassicae with neem, the DGCs were abolished, suggesting direct action on the neuromuscular system. The disappearance of DGCs was accompanied with lethal desiccation, supporting the hypothesis that DGC is an adap...
Veromann, E., Kovacs, G., Kaasik, R., Vaino, L., Karise, R., Päädam, R., Jõgar, K., Veromann, L-L... more Veromann, E., Kovacs, G., Kaasik, R., Vaino, L., Karise, R., Päädam, R., Jõgar, K., Veromann, L-L., Jürgenson, M., Mänd, M. 2015. The abundance and species diversity of pollinators in agricultural landscape elements. – Agronomy 2015. Insect pollination is an important ecosystem service that benefits many food crops. However, the loss and fragmentation of semi-natural and non-crop habitats have drastically diminished the number and species richness of pollinators i.e. the providers of this ecosystem service. Semi-natural habitats such as field margins, grasslands, hedgerows, and woodlands can offer habitats, food resource, shelter, hibernation places etc. for different pollinators. In our study, the impact of different landscape elements on the abundance and species richness of pollinators was measured. Specifically, we compared the abundance and species diversity of pollinators in five landscape elements – two linear elements: herbaceous and woody, and three areal elements: fallow, ...
The aim of the present study was to determine the association and dynamic of small white (Pieris ... more The aim of the present study was to determine the association and dynamic of small white (Pieris rapae L.) on five different white cabbage (Brassica oleracea var. capitata f. alba) cultivars. The experiment showed that butterflies preferred medium cultivar ‛Krautkaiser’ as the site for oviposition; 35.8% of eggs and caterpillars counted during the observation period were gathered from this plant. The next choice was late-maturing cultivar ‛Lennox’ by 21.6%. In comparison with the previous cabbage variants, the butterfly selected the medium cultivar ‛Krautman’ (13.9%) and early cultivar ‛Parel’ (12.3%) as the site for oviposition considerably less.
The aim of the present study was to determine the oviposition preference of Small White (Pieris r... more The aim of the present study was to determine the oviposition preference of Small White (Pieris rapae L.) on five different white cabbage (Brassica oleracea var. capitata f. alba) cultivars. The experiment showed that in first year butterflies preferred late-matured cultivar 'Krautkaizer' as the site for oviposition; 35.8% of eggs counted during the observation period were gathered from this plant. The next choice was mid-season cultivar 'Lennox' by 21.6%. In second year the preferred cultivars were late-matured 'Turquoise' (26%), 'Lennox' (22.1 %) and 'Krautkaizer' (20%). The egg laying activity was high during whole test period in both years of those variants.
We compare standard metabolic rate (VCO2) and gas exchange patterns in the Colorado potato beetle... more We compare standard metabolic rate (VCO2) and gas exchange patterns in the Colorado potato beetle (Leptinotarsa decemlineata Say) in winter diapause (i.e. lasting only one overwintering period) with those of beetles in prolonged diapause (i.e. diapause lasting 2 or 3 years). The length of diapause is estimated by the behaviour of the beetles: burrowing into soil as a sign of the beginning of diapause and emergence from the soil as the ending of diapause. Measurement with a flow‐through carbon dioxide (CO2) infrared gas analyzer reveals that most beetles in winter or prolonged diapause display distinct discontinuous gas exchange cycles at 23 °C. Beetles with cyclic gas exchange and continuous breathing do not survive the winter. Beetles in prolonged diapause are characterized by a three‐ to five‐fold lower standard metabolic rates, longer discontinuous gas exchange periods and shorter CO2 releases (open phase) than those in winter diapause.
The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were mo... more The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were monitored in diapausing Leptinotarsa decemlineata beetles. Measurements were made by means of a flow-through CO2 analyser and a coulometric respirometer. Under the elytra of these beetles there is a more or less tightly enclosed space, the subelytral cavity (SEC). When the cavity was tightly closed, air pressure inside was sub-atmospheric, as a result of oxygen uptake into the tracheae by the beetle. In about half of the beetles, regular opening-closing rhythms of the SEC were observed visually and also recorded; these beetles displayed a discontinuous gas exchange pattern. The SEC opened at the start of the CO2 burst and was immediately closed. On opening, a rapid passive suction inflow of atmospheric air into the SEC occurred, recorded coulometrically as a sharp upward peak. As the CO2 burst lasted beyond the closure of the SEC, we suggest that most of the CO2 was expelled through the me...
Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae),... more Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), were investigated using an infrared gaseous analyser (IRGA) and a coulometric O2 respirometer (manometric–volumetric system). Before testing, the beetles were kept either in dry (dehydrated) or moist (hydrated) conditions for 1 day. Their subsequent gas exchange patterns did not depend on their state of humidity but rather were controlled by the humidity of the insect chamber during gas exchange measurement. If this chamber contained dry air, the beetles exhibited CO2 release by burst, which we interpreted as cyclic gas exchange (CGE) with inter‐burst periods, but if the chamber was switched to contain moist air, then cyclic CO2 release was soon abandoned and a pattern of continuous gas exchange appeared. Measurements with the coulometric respirometer in moist air showed that continuous gas exchange was often associated with weak abdominal pulsations, which we interpreted as active ventilation. Their metabolic rate was lower during gas exchange cycles than during continuous gas exchange. We revealed that in the ladybird beetle metabolic rate increased in moist air when the gas exchange pattern transitioned from cyclic to continuous.
The great web‐spinning pine‐sawfly Acantholyda posticalis Mats. (Hymenoptera: Pamphiliidae) is on... more The great web‐spinning pine‐sawfly Acantholyda posticalis Mats. (Hymenoptera: Pamphiliidae) is one of the major defoliating insects of pine forests. Mass outbreaks of this species have occurred in Scots pine (Pinus sylvestris L.) stands in Central Europe and in the southern parts of Eastern Europe and Siberia. Recently, the outbreak range has shifted northward and new outbreaks have been recorded in Estonia and Finland. The dynamics of the supercooling capability of pre‐imaginal stages of A. posticalis (eonymphs, pronymphs, pupae) collected from the soil in a pine forest on the Island of Saaremaa, Estonia, were determined. The supercooling points (SCP) of overwintering eonymphs and pronymphs changed during the winter, although there were no significant differences between the mean SCPs of either larval stage on any measuring date. The mean SCPs decreased from October (−8 to −10 °C) to January and March (−15 to −17 °C) and increased once again in May (−9 to −11 °C). The average SCP of pupae was considerably higher (−5.3 °C). Overwintering larvae in the soil are potentially covered by an insulating layer of forest litter, moss and snow, thus avoiding direct exposure to low temperatures. Cold‐hardiness in both overwintering larval stages of A. posticalis is sufficient for successful survival during winter in the northern Baltic region. At present, outbreaks of A. posticalis in higher latitudes are concentrated in milder maritime regions near the coast of the Baltic Sea, although these may expand in the future as a result of climate warming, with the sawfly possibly becoming a serious pest of pine forests of northern Europe.
Twelve selected cultivated or wild solanaceae (Solanum dulcamara, Solanum nigrum, Solanum villosu... more Twelve selected cultivated or wild solanaceae (Solanum dulcamara, Solanum nigrum, Solanum villosum, Solanum lycopersicum, Solanum muricatum, Solanum melongena, Datura innoxia, Datura metel, Physalis spp., Capsicum annuum, Nicotiana alata, and Petunia spp.) (all species Solanales: Solanaceae) were tested as potential alternative host plants against Solanum tuberosum for a local population of the Colorado potato beetle Leptinotarsa decemlineata Say (CPB) in Estonia. Some CPB populations in America and southern Europe accept most of these plants. However, geographically isolated populations of beetles can differ in their acceptance of new host plants. Migrants from the southern Europe supplement Estonian beetle population regularly, so individuals may differ in their host plant preferences. S. melongena and S. dulcamara were well accepted by the beetles, Lycopersicum spp. (Solanales: Solanaceae) and N. alata were intermediate, and S. villosum and S. nigrum were least accepted. The beet...
ABSTRACT Oilseed rape (Brassica napus) is a valuable crop, attacked by several insect pests, of w... more ABSTRACT Oilseed rape (Brassica napus) is a valuable crop, attacked by several insect pests, of which the pollen beetle (Meligethes aeneus) is one of the most widespread and important in Europe. The relative attractiveness for the pollen beetle of Brassica nigra, Eruca sativa and Raphanus sativus was compared with that of spring oilseed rape, to assess the potential of these plant species as trap crops for the pest. At early growth stages, B. nigra and R. sativus were more attractive to over-wintered adult pollen beetles than B. napus. At the bud and flowering stages, B. nigra was the most attractive while E. sativa was the least attractive. At flowering, B. nigra was more attractive for oviposition than the other species. Thus, of the species tested, B. nigra has the most potential as a prospective trap crop to protect spring oilseed rape before flowering when it is at its most vulnerable developmental phase, due to its faster development and its acceptability both for feeding and oviposition to overwintered pollen beetle adults. Raphanus sativus was accepted both for feeding and oviposition, but pollen beetle larvae failed to develop in its flowers; it therefore has the potential for use as a dead-end crop. At the end of the growing season, both E. sativa and R. sativus, as late-flowering species, attracted the new generation of pollen beetles and thereby have potential to extend the effectiveness of a trap-cropping system at this time.
Supercooling ability and cold hardiness in the horseradish flea beetle Phyllotreta armoracia (Koc... more Supercooling ability and cold hardiness in the horseradish flea beetle Phyllotreta armoracia (Koch)(Coleoptera: Chrysomelidae: Alticinae) was investigated. Mean supercooling points (SCP) varied from− 10.1 to− 23.9 C depending on the season: SCP ...
Reviewed are the results of treatments carried out in the Institute of Agricultural and Environme... more Reviewed are the results of treatments carried out in the Institute of Agricultural and Environmental Sciences of treatments with natural insecticidal substances on the development and physiological state of insects, using neurotoxical plant extracts (pyrethrins), plant extracts possessing several modes of action (neem) and an Insect Growth Regulator (extract of Ledum palustre possessing properties of juvenile hormone). Physiological changes evoked with treatments were monitored by means of complex methods including a constant volume respirometer, infrared actograph, infrared gas analyzer (IRGA),and a microcalorimeter. Diapausing lepidopterous pupae (Pieris brassicae, Mamestra brassicae) exhibited discontinuous gas exchange cycles (DGCs). After treatments of the pupae of P. brassicae with neem, the DGCs were abolished, suggesting direct action on the neuromuscular system. The disappearance of DGCs was accompanied with lethal desiccation, supporting the hypothesis that DGC is an adap...
Veromann, E., Kovacs, G., Kaasik, R., Vaino, L., Karise, R., Päädam, R., Jõgar, K., Veromann, L-L... more Veromann, E., Kovacs, G., Kaasik, R., Vaino, L., Karise, R., Päädam, R., Jõgar, K., Veromann, L-L., Jürgenson, M., Mänd, M. 2015. The abundance and species diversity of pollinators in agricultural landscape elements. – Agronomy 2015. Insect pollination is an important ecosystem service that benefits many food crops. However, the loss and fragmentation of semi-natural and non-crop habitats have drastically diminished the number and species richness of pollinators i.e. the providers of this ecosystem service. Semi-natural habitats such as field margins, grasslands, hedgerows, and woodlands can offer habitats, food resource, shelter, hibernation places etc. for different pollinators. In our study, the impact of different landscape elements on the abundance and species richness of pollinators was measured. Specifically, we compared the abundance and species diversity of pollinators in five landscape elements – two linear elements: herbaceous and woody, and three areal elements: fallow, ...
The aim of the present study was to determine the association and dynamic of small white (Pieris ... more The aim of the present study was to determine the association and dynamic of small white (Pieris rapae L.) on five different white cabbage (Brassica oleracea var. capitata f. alba) cultivars. The experiment showed that butterflies preferred medium cultivar ‛Krautkaiser’ as the site for oviposition; 35.8% of eggs and caterpillars counted during the observation period were gathered from this plant. The next choice was late-maturing cultivar ‛Lennox’ by 21.6%. In comparison with the previous cabbage variants, the butterfly selected the medium cultivar ‛Krautman’ (13.9%) and early cultivar ‛Parel’ (12.3%) as the site for oviposition considerably less.
The aim of the present study was to determine the oviposition preference of Small White (Pieris r... more The aim of the present study was to determine the oviposition preference of Small White (Pieris rapae L.) on five different white cabbage (Brassica oleracea var. capitata f. alba) cultivars. The experiment showed that in first year butterflies preferred late-matured cultivar 'Krautkaizer' as the site for oviposition; 35.8% of eggs counted during the observation period were gathered from this plant. The next choice was mid-season cultivar 'Lennox' by 21.6%. In second year the preferred cultivars were late-matured 'Turquoise' (26%), 'Lennox' (22.1 %) and 'Krautkaizer' (20%). The egg laying activity was high during whole test period in both years of those variants.
We compare standard metabolic rate (VCO2) and gas exchange patterns in the Colorado potato beetle... more We compare standard metabolic rate (VCO2) and gas exchange patterns in the Colorado potato beetle (Leptinotarsa decemlineata Say) in winter diapause (i.e. lasting only one overwintering period) with those of beetles in prolonged diapause (i.e. diapause lasting 2 or 3 years). The length of diapause is estimated by the behaviour of the beetles: burrowing into soil as a sign of the beginning of diapause and emergence from the soil as the ending of diapause. Measurement with a flow‐through carbon dioxide (CO2) infrared gas analyzer reveals that most beetles in winter or prolonged diapause display distinct discontinuous gas exchange cycles at 23 °C. Beetles with cyclic gas exchange and continuous breathing do not survive the winter. Beetles in prolonged diapause are characterized by a three‐ to five‐fold lower standard metabolic rates, longer discontinuous gas exchange periods and shorter CO2 releases (open phase) than those in winter diapause.
The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were mo... more The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were monitored in diapausing Leptinotarsa decemlineata beetles. Measurements were made by means of a flow-through CO2 analyser and a coulometric respirometer. Under the elytra of these beetles there is a more or less tightly enclosed space, the subelytral cavity (SEC). When the cavity was tightly closed, air pressure inside was sub-atmospheric, as a result of oxygen uptake into the tracheae by the beetle. In about half of the beetles, regular opening-closing rhythms of the SEC were observed visually and also recorded; these beetles displayed a discontinuous gas exchange pattern. The SEC opened at the start of the CO2 burst and was immediately closed. On opening, a rapid passive suction inflow of atmospheric air into the SEC occurred, recorded coulometrically as a sharp upward peak. As the CO2 burst lasted beyond the closure of the SEC, we suggest that most of the CO2 was expelled through the me...
Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae),... more Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), were investigated using an infrared gaseous analyser (IRGA) and a coulometric O2 respirometer (manometric–volumetric system). Before testing, the beetles were kept either in dry (dehydrated) or moist (hydrated) conditions for 1 day. Their subsequent gas exchange patterns did not depend on their state of humidity but rather were controlled by the humidity of the insect chamber during gas exchange measurement. If this chamber contained dry air, the beetles exhibited CO2 release by burst, which we interpreted as cyclic gas exchange (CGE) with inter‐burst periods, but if the chamber was switched to contain moist air, then cyclic CO2 release was soon abandoned and a pattern of continuous gas exchange appeared. Measurements with the coulometric respirometer in moist air showed that continuous gas exchange was often associated with weak abdominal pulsations, which we interpreted as active ventilation. Their metabolic rate was lower during gas exchange cycles than during continuous gas exchange. We revealed that in the ladybird beetle metabolic rate increased in moist air when the gas exchange pattern transitioned from cyclic to continuous.
The great web‐spinning pine‐sawfly Acantholyda posticalis Mats. (Hymenoptera: Pamphiliidae) is on... more The great web‐spinning pine‐sawfly Acantholyda posticalis Mats. (Hymenoptera: Pamphiliidae) is one of the major defoliating insects of pine forests. Mass outbreaks of this species have occurred in Scots pine (Pinus sylvestris L.) stands in Central Europe and in the southern parts of Eastern Europe and Siberia. Recently, the outbreak range has shifted northward and new outbreaks have been recorded in Estonia and Finland. The dynamics of the supercooling capability of pre‐imaginal stages of A. posticalis (eonymphs, pronymphs, pupae) collected from the soil in a pine forest on the Island of Saaremaa, Estonia, were determined. The supercooling points (SCP) of overwintering eonymphs and pronymphs changed during the winter, although there were no significant differences between the mean SCPs of either larval stage on any measuring date. The mean SCPs decreased from October (−8 to −10 °C) to January and March (−15 to −17 °C) and increased once again in May (−9 to −11 °C). The average SCP of pupae was considerably higher (−5.3 °C). Overwintering larvae in the soil are potentially covered by an insulating layer of forest litter, moss and snow, thus avoiding direct exposure to low temperatures. Cold‐hardiness in both overwintering larval stages of A. posticalis is sufficient for successful survival during winter in the northern Baltic region. At present, outbreaks of A. posticalis in higher latitudes are concentrated in milder maritime regions near the coast of the Baltic Sea, although these may expand in the future as a result of climate warming, with the sawfly possibly becoming a serious pest of pine forests of northern Europe.
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