Reported are the results of Y-tube olfactometer bioassays on the behavioural responses of T. taba... more Reported are the results of Y-tube olfactometer bioassays on the behavioural responses of T. tabaci to the flower odours p-anisaldehyde and benzaldehyde (benzoic aldehyde). Interference of clover volatiles and these flower odours on the orientation of adult onion thrips was tested in a field experiment. Olfactory bioassays demonstrated purified flower odours (aldehydes) were attractive to adult females of the onion
ABSTRACT Themaboek PPO 303 uitgegeven naar aanleiding van de studiedag met gelijknamige titel op ... more ABSTRACT Themaboek PPO 303 uitgegeven naar aanleiding van de studiedag met gelijknamige titel op 14 maart 2002 in het WICC te Wageningen, georganiseerd door Praktijkonderzoek Plant & Omgeving en Plant Research International onder auspiciën van het Innovatiecentrum Biologische Landbouw
... Kick the pesticide habit: forces affecting ... The development of integrated systems (integra... more ... Kick the pesticide habit: forces affecting ... The development of integrated systems (integrated pest management, IPM and integrated crop management, ICM) in combination with farmer participatory learning in Farmer Field Schools, have resulted in a better use of external inputs ...
Electron microscopic studies of the interaction of second-stage juveniles ofMeloidogyne hapla and... more Electron microscopic studies of the interaction of second-stage juveniles ofMeloidogyne hapla andArthrobotrys oligospora (CBS 289.82) strongly suggest that hyphae attachment to nematodes was mediated by a 0.1µm thick layer matrix between the fungus and prey after contact with the nematode cuticle. The amorphous electron opaque matrix was irregularly distributed over the fungal surface, in some cases covering only the side
ABSTRACT Suppressive effects of intercropping on Frankliniella occidentalis (Pergande) infestatio... more ABSTRACT Suppressive effects of intercropping on Frankliniella occidentalis (Pergande) infestations have been reported in several crops. However, this study demonstrates that in year-round chrysanthemum, Dendranthema grandiflora Tzvelev, undersowing with subterranean clover, Trifolium subterraneum L., results in an increased thrips feeding damage. In a pot experiment, performed with chrysanthemum plants (cultivars Reagan and Tiger) grown with or without subterranean clover, significantly more leaves with silver and growth damage were found in the chrysanthemum plants with subterranean clover in comparison with the monocropped chrysanthemum plants. Similarly, the degree of deformation of leaf perimeter and leaf surface was higher in the top leaves of the intercropped chrysanthemum plant. In the soil experiment (only performed with Tiger and plants were grown in the soil in the greenhouse) intercropped chrysanthemum plants suffered a higher feeding damage as well. Analysis of the relation between silver or growth damage and the thrips pressure demonstrates that at similar thrips pressure in the intercropped chrysanthemum plants suffered significantly more damage. The higher thrips pressure in the intercropped chrysanthemum only explains the differences in damage partly. Changes in the reaction of chrysanthemum plants to thrips feeding or in the behaviour of the thrips, mediated by the presence of the non-host crop, are discussed. Our explanation is that chrysanthemum plants grown with clover are more susceptible to thrips feeding than monocropped plants. We conclude that undersowing with clover does not contribute to reduce damage by F.occidentalis in year-round chrysanthemum. Also, the influence of crop diversification on a pest cannot be foreseen until the specific characteristics of each individual crop – pest system are studied.
ABSTRACT The suppressive effects of undersown clover on Thrips tabaci Lindeman infestation in lee... more ABSTRACT The suppressive effects of undersown clover on Thrips tabaci Lindeman infestation in leek is known but not the stages in thrips population dynamics that are affected by intercropping and the mechanisms involved. Colonization or settling of adult onion thrips (T. tabaci) in monocropped leek (Allium porrum L.) and in leek intercropped with strawberry clover (Trifolium fragiferum L.) was studied in two potted plant experiments. Potted leek plants with and without undersown clover were placed for a short period (2 and 5 days) in monocropped or intercropped field plots when high thrips infestation was expected. Thrips adults were counted on all leaves and in the shaft during this observation period. Thrips populations were monitored weekly in the field plots throughout the entire growing season.In both potted plant experiments, there were consistently fewer thrips adults on intercropped leek plants than on monocropped plants. The plant growth parameters – number of leaves and stem diameter – were similar in all treatments and thus did not explain differences in thrips adults. Natural enemies were absent on both leek and clover, and thus cannot explain the differences in adult thrips numbers. Furthermore, no adults of T. tabaci were found on the clover in the potted plant experiment and only very few in the field experiment. Thus it was concluded that strawberry clover was not an effective trap crop for thrips.In the second potted plant experiment, clover was removed just before the leek plants were introduced to the field, thus eliminating direct physical, visual and olfactory interference by clover. After the undersown clover was removed, the leek plants harboured only one-third of the number of thrips adults, as compared to the monocropped plants. This study supports the notion that there are subtle links between intercropping and plant quality, and indicates that host-plant quality is an underlying cause of the reduction in adult thrips numbers in leek/clover intercropping.
Reported are the results of Y-tube olfactometer bioassays on the behavioural responses of T. taba... more Reported are the results of Y-tube olfactometer bioassays on the behavioural responses of T. tabaci to the flower odours p-anisaldehyde and benzaldehyde (benzoic aldehyde). Interference of clover volatiles and these flower odours on the orientation of adult onion thrips was tested in a field experiment. Olfactory bioassays demonstrated purified flower odours (aldehydes) were attractive to adult females of the onion
ABSTRACT Themaboek PPO 303 uitgegeven naar aanleiding van de studiedag met gelijknamige titel op ... more ABSTRACT Themaboek PPO 303 uitgegeven naar aanleiding van de studiedag met gelijknamige titel op 14 maart 2002 in het WICC te Wageningen, georganiseerd door Praktijkonderzoek Plant & Omgeving en Plant Research International onder auspiciën van het Innovatiecentrum Biologische Landbouw
... Kick the pesticide habit: forces affecting ... The development of integrated systems (integra... more ... Kick the pesticide habit: forces affecting ... The development of integrated systems (integrated pest management, IPM and integrated crop management, ICM) in combination with farmer participatory learning in Farmer Field Schools, have resulted in a better use of external inputs ...
Electron microscopic studies of the interaction of second-stage juveniles ofMeloidogyne hapla and... more Electron microscopic studies of the interaction of second-stage juveniles ofMeloidogyne hapla andArthrobotrys oligospora (CBS 289.82) strongly suggest that hyphae attachment to nematodes was mediated by a 0.1µm thick layer matrix between the fungus and prey after contact with the nematode cuticle. The amorphous electron opaque matrix was irregularly distributed over the fungal surface, in some cases covering only the side
ABSTRACT Suppressive effects of intercropping on Frankliniella occidentalis (Pergande) infestatio... more ABSTRACT Suppressive effects of intercropping on Frankliniella occidentalis (Pergande) infestations have been reported in several crops. However, this study demonstrates that in year-round chrysanthemum, Dendranthema grandiflora Tzvelev, undersowing with subterranean clover, Trifolium subterraneum L., results in an increased thrips feeding damage. In a pot experiment, performed with chrysanthemum plants (cultivars Reagan and Tiger) grown with or without subterranean clover, significantly more leaves with silver and growth damage were found in the chrysanthemum plants with subterranean clover in comparison with the monocropped chrysanthemum plants. Similarly, the degree of deformation of leaf perimeter and leaf surface was higher in the top leaves of the intercropped chrysanthemum plant. In the soil experiment (only performed with Tiger and plants were grown in the soil in the greenhouse) intercropped chrysanthemum plants suffered a higher feeding damage as well. Analysis of the relation between silver or growth damage and the thrips pressure demonstrates that at similar thrips pressure in the intercropped chrysanthemum plants suffered significantly more damage. The higher thrips pressure in the intercropped chrysanthemum only explains the differences in damage partly. Changes in the reaction of chrysanthemum plants to thrips feeding or in the behaviour of the thrips, mediated by the presence of the non-host crop, are discussed. Our explanation is that chrysanthemum plants grown with clover are more susceptible to thrips feeding than monocropped plants. We conclude that undersowing with clover does not contribute to reduce damage by F.occidentalis in year-round chrysanthemum. Also, the influence of crop diversification on a pest cannot be foreseen until the specific characteristics of each individual crop – pest system are studied.
ABSTRACT The suppressive effects of undersown clover on Thrips tabaci Lindeman infestation in lee... more ABSTRACT The suppressive effects of undersown clover on Thrips tabaci Lindeman infestation in leek is known but not the stages in thrips population dynamics that are affected by intercropping and the mechanisms involved. Colonization or settling of adult onion thrips (T. tabaci) in monocropped leek (Allium porrum L.) and in leek intercropped with strawberry clover (Trifolium fragiferum L.) was studied in two potted plant experiments. Potted leek plants with and without undersown clover were placed for a short period (2 and 5 days) in monocropped or intercropped field plots when high thrips infestation was expected. Thrips adults were counted on all leaves and in the shaft during this observation period. Thrips populations were monitored weekly in the field plots throughout the entire growing season.In both potted plant experiments, there were consistently fewer thrips adults on intercropped leek plants than on monocropped plants. The plant growth parameters – number of leaves and stem diameter – were similar in all treatments and thus did not explain differences in thrips adults. Natural enemies were absent on both leek and clover, and thus cannot explain the differences in adult thrips numbers. Furthermore, no adults of T. tabaci were found on the clover in the potted plant experiment and only very few in the field experiment. Thus it was concluded that strawberry clover was not an effective trap crop for thrips.In the second potted plant experiment, clover was removed just before the leek plants were introduced to the field, thus eliminating direct physical, visual and olfactory interference by clover. After the undersown clover was removed, the leek plants harboured only one-third of the number of thrips adults, as compared to the monocropped plants. This study supports the notion that there are subtle links between intercropping and plant quality, and indicates that host-plant quality is an underlying cause of the reduction in adult thrips numbers in leek/clover intercropping.
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