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S E Learmonth - One of the best experts on this subject based on the ideXlab platform.
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impact of the Soil Insects african black beetle heteronychus arator coleoptera scarabaeidae and whitefringed weevil graphognathus leucoloma coleoptera curculionidae on potatoes and effects of Soil insecticide treatments in south western australia
Bulletin of Entomological Research, 1995Co-Authors: J N Matthiessen, S E LearmonthAbstract:Populations of the Soil Insects African black beetle, Heteronychus arator (Fabricius), and whitefringed weevil, Graphognathus leucoloma (Boheman), and the damage caused to potato crops in south-western Australia were measured with and without the insecticide chlorpyrifos incorporated into the Soil prior to planting. Low populations of both Insects were highly damaging. Destruction of stems by H. arator reduced tuber yield and both species damaged tubers from the time of their formation. Tuber damage increased with time because both insect species on average damaged multiple tubers and caused multiple attacks on tubers. Growth of G. leucoloma larvae caused increased abundance of the more damaging later instars in spring. The insecticide reduced resident H. arator abundance and hence damage to newly-emerging potato stems in summer, but had less effect on reducing attacks on tubers in summer crops because adult beetles flew into some crops during growth. Exceptionally high tuber damage per H. arator adult in winter crops was ascribed to enhanced activity during its spring breeding season. The insecticide was inconsistent in reducing the abundance of G. leucoloma larvae. Insecticidal effects were greatest near the Soil surface, resulting in an increase in the relative proportion of both Insects deeper in the Soil. Since a greater proportion of the tubers occurred there, the resulting greater potential for the Insects to cause tuber damage tended to outweigh reduction in their abundance.
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Spatial sampling of Insects, plant parts and insect attacks in the Soil of potato crops
Bulletin of Entomological Research, 1993Co-Authors: J N Matthiessen, S E LearmonthAbstract:A method was devised for spatial sampling within the Soil in potato crops where the Soil Insects African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae) and whitefringed weevil, Graphognathus leucoloma (Boheman) (Coleoptera: Curculionidae) are pests. The number and position of potato plant parts, the Soil Insects, and their attacks on potatoes were defined within the hilled-up Soil profile of sections of the planting rows. Neither potato tubers, nor Insects nor insect attacks were uniformly distributed. Tubers occurred mainly in the middle of the hill, while the Insects contrasted in their distribution in the Soil. Most of the damaging H. arator adults and larvae occurred in upper middle areas; the damaging G. leucoloma larvae occurred deeper and were more damaging on the under-side of tubers. The method provides a means of simultaneously sampling Soil insect populations in a crop and obtaining a direct assessment of their damage and the effectiveness of control measures.
J N Matthiessen - One of the best experts on this subject based on the ideXlab platform.
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impact of the Soil Insects african black beetle heteronychus arator coleoptera scarabaeidae and whitefringed weevil graphognathus leucoloma coleoptera curculionidae on potatoes and effects of Soil insecticide treatments in south western australia
Bulletin of Entomological Research, 1995Co-Authors: J N Matthiessen, S E LearmonthAbstract:Populations of the Soil Insects African black beetle, Heteronychus arator (Fabricius), and whitefringed weevil, Graphognathus leucoloma (Boheman), and the damage caused to potato crops in south-western Australia were measured with and without the insecticide chlorpyrifos incorporated into the Soil prior to planting. Low populations of both Insects were highly damaging. Destruction of stems by H. arator reduced tuber yield and both species damaged tubers from the time of their formation. Tuber damage increased with time because both insect species on average damaged multiple tubers and caused multiple attacks on tubers. Growth of G. leucoloma larvae caused increased abundance of the more damaging later instars in spring. The insecticide reduced resident H. arator abundance and hence damage to newly-emerging potato stems in summer, but had less effect on reducing attacks on tubers in summer crops because adult beetles flew into some crops during growth. Exceptionally high tuber damage per H. arator adult in winter crops was ascribed to enhanced activity during its spring breeding season. The insecticide was inconsistent in reducing the abundance of G. leucoloma larvae. Insecticidal effects were greatest near the Soil surface, resulting in an increase in the relative proportion of both Insects deeper in the Soil. Since a greater proportion of the tubers occurred there, the resulting greater potential for the Insects to cause tuber damage tended to outweigh reduction in their abundance.
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Spatial sampling of Insects, plant parts and insect attacks in the Soil of potato crops
Bulletin of Entomological Research, 1993Co-Authors: J N Matthiessen, S E LearmonthAbstract:A method was devised for spatial sampling within the Soil in potato crops where the Soil Insects African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae) and whitefringed weevil, Graphognathus leucoloma (Boheman) (Coleoptera: Curculionidae) are pests. The number and position of potato plant parts, the Soil Insects, and their attacks on potatoes were defined within the hilled-up Soil profile of sections of the planting rows. Neither potato tubers, nor Insects nor insect attacks were uniformly distributed. Tubers occurred mainly in the middle of the hill, while the Insects contrasted in their distribution in the Soil. Most of the damaging H. arator adults and larvae occurred in upper middle areas; the damaging G. leucoloma larvae occurred deeper and were more damaging on the under-side of tubers. The method provides a means of simultaneously sampling Soil insect populations in a crop and obtaining a direct assessment of their damage and the effectiveness of control measures.
David M Eissenstat - One of the best experts on this subject based on the ideXlab platform.
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Soil Insects alter fine root demography in peach prunus persica
Plant Cell and Environment, 2002Co-Authors: Christina E Wells, D M Glenn, David M EissenstatAbstract:Minirhizotrons were used to assess the effects of Soil insect suppression on the demography of peach fine roots (<1 mm diameter) over two growing seasons. The experiment was conducted at the USDA-ARS Appalachian Fruit Research Station in Kearneysville, WV, USA using six 15-year-old peach trees. Clear butyrate minirhizotrons were installed beneath each tree in April 1996. Soil drench treatments were applied around individual minirhizotron tubes at monthly intervals and consisted of 1 L of water or 250 μL of a broad-spectrum insecticide in 1 L of water. Roots were videotaped at 2- to 4-week intervals during the 1996 and 1997 growing seasons. Insecticide application was associated with a significant increase in fine root longevity: the median lifespans of insecticide-treated roots were 46-125 d longer than those of control roots. In addition, the development of brown pigmentation was significantly delayed in insecticide-treated roots. Insecticide application did not appear to increase Soil fertility, as accumulation of NO 3 -, NH 4 +, and PO 4 2- on mixed bed ion-exchange resin was similar in treated and untreated Soil. These results suggest that interactions with below-ground Insects can significantly influence root longevity and may alter the rate at which roots undergo developmental changes in anatomy and physiology.
P L Mafongoya - One of the best experts on this subject based on the ideXlab platform.
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effect of rotational fallows on abundance of Soil Insects and weeds in maize crops in eastern zambia
Applied Soil Ecology, 2003Co-Authors: Gudeta W Sileshi, P L MafongoyaAbstract:Abstract Improved fallows or the rotation of fast growing nitrogen-fixing legume species with cereals have been shown to accumulate nitrogen and organic matter, recycle nutrients in the Soil and improve Soil physical and chemical properties, and increase crop yield compared to traditional fallows. However, the effect of Soil nutrients added by fallow species on the incidence of pests, weeds and pathogens in the subsequent crop has not been assessed in southern Africa. In this study, we assessed the relationships between nutrients in the Soil after fallows of crotalaria ( Crotalaria grahamiana ), pigeon pea ( Cajanus cajan ), sesbania ( Sesbania sesban ), tephrosia ( Tephrosia vogelii ), and their mixtures, and the incidence of Soil Insects, namely, snout beetles ( Diaecoderus sp.) and termites, and weeds in eastern Zambia. Rotational fallows of sesbania+crotalaria, sesbania+tephrosia, sesbania+pigeon pea and tephrosia+pigeon pea increased infestation of maize by snout beetles as compared to the natural fallow or unfertilised maize grown continuously in monoculture. The beetles showed aggregated spatial distribution, influenced mainly by the nitrate and total inorganic nitrogen content of the Soil. Termite incidence was higher in maize after a natural fallow and pure crotalaria, which had 11 and 7 times as much damage as maize planted after pigeon pea+tephrosia mixture. Total weed biomass in maize grown after a natural fallow was six times higher than in maize planted after pure sesbania fallows. The weed biomass was correlated positively with the potassium content of the top 20 cm Soil and negatively with plant litter on the Soil surface. It is concluded that organic inputs from pure sesbania, sesbania+pigeon pea, sesbania+tephrosia and tephrosia+pigeon pea reduce infestation by termites and weeds, and give maize grain yield comparable with the recommended rates of inorganic fertilisers. However, these fallows have the potential to increase infestation by snout beetles. This is the first study on the snout beetle in Africa, and we recommend more systematic investigation on its ecology in agroforestry systems.
Christina E Wells - One of the best experts on this subject based on the ideXlab platform.
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Soil Insects alter fine root demography in peach prunus persica
Plant Cell and Environment, 2002Co-Authors: Christina E Wells, D M Glenn, David M EissenstatAbstract:Minirhizotrons were used to assess the effects of Soil insect suppression on the demography of peach fine roots (<1 mm diameter) over two growing seasons. The experiment was conducted at the USDA-ARS Appalachian Fruit Research Station in Kearneysville, WV, USA using six 15-year-old peach trees. Clear butyrate minirhizotrons were installed beneath each tree in April 1996. Soil drench treatments were applied around individual minirhizotron tubes at monthly intervals and consisted of 1 L of water or 250 μL of a broad-spectrum insecticide in 1 L of water. Roots were videotaped at 2- to 4-week intervals during the 1996 and 1997 growing seasons. Insecticide application was associated with a significant increase in fine root longevity: the median lifespans of insecticide-treated roots were 46-125 d longer than those of control roots. In addition, the development of brown pigmentation was significantly delayed in insecticide-treated roots. Insecticide application did not appear to increase Soil fertility, as accumulation of NO 3 -, NH 4 +, and PO 4 2- on mixed bed ion-exchange resin was similar in treated and untreated Soil. These results suggest that interactions with below-ground Insects can significantly influence root longevity and may alter the rate at which roots undergo developmental changes in anatomy and physiology.