Effects of three diets: (1) complete diet; (2) supplemental diet (vitamin and mineral supplements... more Effects of three diets: (1) complete diet; (2) supplemental diet (vitamin and mineral supplements not added); and (3) the supplemental diet with an adjunct organic fertilization regimen (using distiller's dried grains with solubles [DDGS]) on benthic macroinvertebrate populations and water quality in experimental ponds used to culture freshwater prawns, Macrobrachium rosenbergii were investigated. Benthic samples were taken from deep (1.5 m) and shallow (1.0 m) areas of each of nine 0.02-ha ponds every three weeks, using a 0.09-m2 Ekman dredge. The abundance of gastro-pods, oligochaetes, total non-insects, chironomids, total dipterans, total insects, and total macroinvertebrates was significantly higher (P <0.05) in ponds receiving the complete diet, possibly due to lower predatory pressure by prawns or direct benefits of micronutri-ents. Total macroinvertebrate abundance was significantly decreased (P <0.05) in ponds receiving supplemental diet (with and without organic fertilization), possibly due to increased predation by prawns to supplement the nutrition not provided by the lower quality diet. Organic fertilization significantly increased (P <0.05) the abundance of oligochaetes and total macroinvertebrates. These data suggest that M. rosenbergii can adjust to reduced feed quality by increasing consumption of benthic fauna.
Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichom... more Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichome secretions of one cultivar of tomato,Lycopersicon esculentum, and 11 accessions ofL. hirsutum consisting of seven accessions ofL. hirsutum f.typicum and four accessions ofL. hirsutum f.glabratum. Leaves of f.typicum were more repellent to mites than were those of f.glabratum orL. esculentum. Removal of trichomes and their secretions by wiping leaves of f.typicum accessions with 95% ethanol rendered them less repellent, indicating that trichomes or their secretions were potentially responsible for repellency. Gas and thin-layer chromatography of leaflet washes obtained by steeping leaflets in hexane indicated that the chemical composition of the washes differed among accessions. The main difference between botanical forms was the presence in leaflet washes from f.typicum accessions of compounds eluting late on the gas Chromatograph and migrating further on reverse-phase thin-layer chromatography; compounds having these characteristics were absent in washes of f.glabratum andL. esculentum. The compositions of secretions taken directly from type I, type IV, and type VI trichomes were similar to that of the leaflet wash obtained from the same f.typicum plant, indicating that leaflet washes contained mainly compounds of trichomal origin. Leaflet washes from f.typicum plants were generally more repellent toT. urticae than were washes from f.glabratum when tested by choice and nonchoice bioassays. Taken together, the data indicate that trichome secretions of f.typicum are likely responsible for potent repellency to two-spotted spider mites observed in this taxon; the likely active compounds are sesquiterpene acids or other polar constituents of trichome secretions.
Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with... more Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with a novel tube-trap bioassay. The relative numbers of flies caught in tube traps baited with enzymatic yeast hydrolysate, brewer's yeast, andn-dipropyl disulfide were similar to those obtained previously with cone traps in the field. Changing the shape of the bioassay cage from a cuboid to a cylinder decreased the experimental error obtained from analysis of variance, as did rotating the floor of the circular cage. This bioassay should be useful in evaluating attractants for other insects that orient along the substrate.
A laboratory experiment was conducted to quantify the effects of infestation of maize by Sitotrog... more A laboratory experiment was conducted to quantify the effects of infestation of maize by Sitotroga cerealella (Olivier) on progeny production by two common secondary colonizers of grain, Tribolium castaneum (Herbst) and Oryzaephilus surinamensis (L.). Adults of both secondary pest species were allowed to oviposit for 3 wk on intact kernels of &#39;DeKalb 689&#39;, mechanically split kernels, kernels that had been infested for 3 mo by S. cerealella, and kernels that had been infested for 6 mo. Progeny of both species reached highest numbers on 6-mo infested maize. Prior infestation for 6 mo by S. cerealella makes maize a more suitable medium for reproduction by T. castaneum and O. surinamensis, much more than can be accounted for by mere disruption of kernel integrity resulting from larval feeding. The results highlight the importance of limiting establishment by S. cerealella on maize in storage.
Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval ... more Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. The insect is univoltine, with larvae active in spring and adults throughout the summer months. Experiments were conducted to determine the depth of pupation in the soil; the impact of substrate texture, moisture content, and temperature on pupation success; and ability of entomopathogenic nematodes to kill larvae when they enter the substrate to pupate. Larvae burrowed only a short distance into the substrate when pupating; 97-100% were found within the top 3 cm of a column of soil or sand and soil mixture in the laboratory. Larval mortality before pupation was low at 22 degrees C but considerably higher at 30 degrees C; at both temperatures, pupation success was lowest on a mixed substrate and higher (and equivalent) on sand or soil alone. Survivorship to adult was influenced by both temperature and substrate moisture content; at 22 degrees C, 56% percent of pupating larvae emerged as adults at 75% moisture content compared with only 25 at 25% moisture content. Emergence of adults was negligible at 30 degrees C, regardless of moisture content. Heterorhabditis bacteriophora and Steinernema carpocapsae were very effective biocontrol agents in laboratory bioassays, reducing adult emergence by 76-100%, with nematode applications made before pupation being more effective than those made after pupation, and H. bacteriophora consistently (but not significantly) more effective than S. carpocapsae. Management methods that take advantage of pupation behaviors are discussed.
Viburnum leaf beetle, Pyrrhalta viburni (Paykull) (Coleoptera: Chrysomelidae), oviposits in termi... more Viburnum leaf beetle, Pyrrhalta viburni (Paykull) (Coleoptera: Chrysomelidae), oviposits in terminal twigs of Viburnum spp. shrubs (Caprifoliaceae). Twigs react to oviposition by producing neoplasm that overgrows the egg mass. Pyrrhalta viburni oviposition behavior is aggregative: females prefer to lay egg masses on twigs previously infested by other females and to position their egg masses adjacent to existing ones. Female oviposition preferences were studied in a series of choice tests under laboratory conditions. The three components of the egg mass (cavity, eggs, and egg cap) were not sufficient to elicit complete aggregation oviposition response when presented separately. Cavity and egg cap elicited positional preference, but not the artificial cavity, artificial egg cap, or frass, suggesting that stimulatory cues might be associated with insect saliva and egg cap secretion. Females preferred to lay eggs on twigs that had produced wound tissue in response to previous oviposition. We conclude that twig choice and positional preference for oviposition are likely to be dissociated, and that twig wound response might be used by P. viburni females to locate twigs already infested and possibly less defended against subsequent oviposition. Pyrrhalta viburni females preferred to lay egg masses on heavily infested twigs rather than on lightly infested twigs. Females did not show preference for twigs infested with their own egg masses, but laid more egg masses on twigs infested by multiple females than on twigs infested by single females. We conclude that both egg mass and conspecific density affect oviposition preferences of P. viburni and discuss the possible ecological implications of this behavior.
Pyrrhalta viburni Paykull, a new landscape pest in the United States, feeds in both the larval an... more Pyrrhalta viburni Paykull, a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. We measured lifetime oviposition capacity of mated and unmated females reared in the laboratory versus field-collected females, as well as ovipositional response to physical characteristics of the host plant. Both mated and unmated females produced eggs, but at different rates. Field-collected females and mated females reared in the laboratory laid similar numbers of egg masses containing similar numbers of eggs, but unmated females laid approximately one half as many eggs, the result primarily of smaller clutch size. Mated females reared in the laboratory had a preovipositional period of 11.4 +/- 1.7 versus 29 + 11.7 d for unmated females, and unmated females lived significantly longer than mated females. The angle and diameter of stems of V. trilobum, a very susceptible host, both greatly influenced oviposition; females laid most eggs on vertically oriented stems, and those of smallest diameter; when these factors were combined, stem diameter predominated. Females also had a very strong geotactic response, preferring to lay eggs on portions of stems toward gravity, even when stems were at fairly shallow angles.
Effects of three diets: (1) complete diet; (2) supplemental diet (vitamin and mineral supplements... more Effects of three diets: (1) complete diet; (2) supplemental diet (vitamin and mineral supplements not added); and (3) the supplemental diet with an adjunct organic fertilization regimen (using distiller's dried grains with solubles [DDGS]) on benthic macroinvertebrate populations and water quality in experimental ponds used to culture freshwater prawns, Macrobrachium rosenbergii were investigated. Benthic samples were taken from deep (1.5 m) and shallow (1.0 m) areas of each of nine 0.02-ha ponds every three weeks, using a 0.09-m2 Ekman dredge. The abundance of gastro-pods, oligochaetes, total non-insects, chironomids, total dipterans, total insects, and total macroinvertebrates was significantly higher (P <0.05) in ponds receiving the complete diet, possibly due to lower predatory pressure by prawns or direct benefits of micronutri-ents. Total macroinvertebrate abundance was significantly decreased (P <0.05) in ponds receiving supplemental diet (with and without organic fertilization), possibly due to increased predation by prawns to supplement the nutrition not provided by the lower quality diet. Organic fertilization significantly increased (P <0.05) the abundance of oligochaetes and total macroinvertebrates. These data suggest that M. rosenbergii can adjust to reduced feed quality by increasing consumption of benthic fauna.
Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichom... more Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichome secretions of one cultivar of tomato,Lycopersicon esculentum, and 11 accessions ofL. hirsutum consisting of seven accessions ofL. hirsutum f.typicum and four accessions ofL. hirsutum f.glabratum. Leaves of f.typicum were more repellent to mites than were those of f.glabratum orL. esculentum. Removal of trichomes and their secretions by wiping leaves of f.typicum accessions with 95% ethanol rendered them less repellent, indicating that trichomes or their secretions were potentially responsible for repellency. Gas and thin-layer chromatography of leaflet washes obtained by steeping leaflets in hexane indicated that the chemical composition of the washes differed among accessions. The main difference between botanical forms was the presence in leaflet washes from f.typicum accessions of compounds eluting late on the gas Chromatograph and migrating further on reverse-phase thin-layer chromatography; compounds having these characteristics were absent in washes of f.glabratum andL. esculentum. The compositions of secretions taken directly from type I, type IV, and type VI trichomes were similar to that of the leaflet wash obtained from the same f.typicum plant, indicating that leaflet washes contained mainly compounds of trichomal origin. Leaflet washes from f.typicum plants were generally more repellent toT. urticae than were washes from f.glabratum when tested by choice and nonchoice bioassays. Taken together, the data indicate that trichome secretions of f.typicum are likely responsible for potent repellency to two-spotted spider mites observed in this taxon; the likely active compounds are sesquiterpene acids or other polar constituents of trichome secretions.
Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with... more Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with a novel tube-trap bioassay. The relative numbers of flies caught in tube traps baited with enzymatic yeast hydrolysate, brewer's yeast, andn-dipropyl disulfide were similar to those obtained previously with cone traps in the field. Changing the shape of the bioassay cage from a cuboid to a cylinder decreased the experimental error obtained from analysis of variance, as did rotating the floor of the circular cage. This bioassay should be useful in evaluating attractants for other insects that orient along the substrate.
A laboratory experiment was conducted to quantify the effects of infestation of maize by Sitotrog... more A laboratory experiment was conducted to quantify the effects of infestation of maize by Sitotroga cerealella (Olivier) on progeny production by two common secondary colonizers of grain, Tribolium castaneum (Herbst) and Oryzaephilus surinamensis (L.). Adults of both secondary pest species were allowed to oviposit for 3 wk on intact kernels of &#39;DeKalb 689&#39;, mechanically split kernels, kernels that had been infested for 3 mo by S. cerealella, and kernels that had been infested for 6 mo. Progeny of both species reached highest numbers on 6-mo infested maize. Prior infestation for 6 mo by S. cerealella makes maize a more suitable medium for reproduction by T. castaneum and O. surinamensis, much more than can be accounted for by mere disruption of kernel integrity resulting from larval feeding. The results highlight the importance of limiting establishment by S. cerealella on maize in storage.
Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval ... more Pyrrhalta viburni (Paykull), a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. The insect is univoltine, with larvae active in spring and adults throughout the summer months. Experiments were conducted to determine the depth of pupation in the soil; the impact of substrate texture, moisture content, and temperature on pupation success; and ability of entomopathogenic nematodes to kill larvae when they enter the substrate to pupate. Larvae burrowed only a short distance into the substrate when pupating; 97-100% were found within the top 3 cm of a column of soil or sand and soil mixture in the laboratory. Larval mortality before pupation was low at 22 degrees C but considerably higher at 30 degrees C; at both temperatures, pupation success was lowest on a mixed substrate and higher (and equivalent) on sand or soil alone. Survivorship to adult was influenced by both temperature and substrate moisture content; at 22 degrees C, 56% percent of pupating larvae emerged as adults at 75% moisture content compared with only 25 at 25% moisture content. Emergence of adults was negligible at 30 degrees C, regardless of moisture content. Heterorhabditis bacteriophora and Steinernema carpocapsae were very effective biocontrol agents in laboratory bioassays, reducing adult emergence by 76-100%, with nematode applications made before pupation being more effective than those made after pupation, and H. bacteriophora consistently (but not significantly) more effective than S. carpocapsae. Management methods that take advantage of pupation behaviors are discussed.
Viburnum leaf beetle, Pyrrhalta viburni (Paykull) (Coleoptera: Chrysomelidae), oviposits in termi... more Viburnum leaf beetle, Pyrrhalta viburni (Paykull) (Coleoptera: Chrysomelidae), oviposits in terminal twigs of Viburnum spp. shrubs (Caprifoliaceae). Twigs react to oviposition by producing neoplasm that overgrows the egg mass. Pyrrhalta viburni oviposition behavior is aggregative: females prefer to lay egg masses on twigs previously infested by other females and to position their egg masses adjacent to existing ones. Female oviposition preferences were studied in a series of choice tests under laboratory conditions. The three components of the egg mass (cavity, eggs, and egg cap) were not sufficient to elicit complete aggregation oviposition response when presented separately. Cavity and egg cap elicited positional preference, but not the artificial cavity, artificial egg cap, or frass, suggesting that stimulatory cues might be associated with insect saliva and egg cap secretion. Females preferred to lay eggs on twigs that had produced wound tissue in response to previous oviposition. We conclude that twig choice and positional preference for oviposition are likely to be dissociated, and that twig wound response might be used by P. viburni females to locate twigs already infested and possibly less defended against subsequent oviposition. Pyrrhalta viburni females preferred to lay egg masses on heavily infested twigs rather than on lightly infested twigs. Females did not show preference for twigs infested with their own egg masses, but laid more egg masses on twigs infested by multiple females than on twigs infested by single females. We conclude that both egg mass and conspecific density affect oviposition preferences of P. viburni and discuss the possible ecological implications of this behavior.
Pyrrhalta viburni Paykull, a new landscape pest in the United States, feeds in both the larval an... more Pyrrhalta viburni Paykull, a new landscape pest in the United States, feeds in both the larval and adult stages on foliage of plants in the genus Viburnum. We measured lifetime oviposition capacity of mated and unmated females reared in the laboratory versus field-collected females, as well as ovipositional response to physical characteristics of the host plant. Both mated and unmated females produced eggs, but at different rates. Field-collected females and mated females reared in the laboratory laid similar numbers of egg masses containing similar numbers of eggs, but unmated females laid approximately one half as many eggs, the result primarily of smaller clutch size. Mated females reared in the laboratory had a preovipositional period of 11.4 +/- 1.7 versus 29 + 11.7 d for unmated females, and unmated females lived significantly longer than mated females. The angle and diameter of stems of V. trilobum, a very susceptible host, both greatly influenced oviposition; females laid most eggs on vertically oriented stems, and those of smallest diameter; when these factors were combined, stem diameter predominated. Females also had a very strong geotactic response, preferring to lay eggs on portions of stems toward gravity, even when stems were at fairly shallow angles.
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