摘要:

The vertical distribution of pear thrips,Taeniothrips inconsequens(Uzel), in forest soils of three drainage classes was investigated. Thrips were extracted from soil cores collected in October 1989 and 1990 from well-drained, moderately well-drained, and poorly drained soils in Pennsylvania sugar maple stands. In both years, the majority of pear thrips occurred in the upper 10 cm of all soils regardless of drainage class. The number of thrips decreased with increasing soil depth in all soils. Thrips were present in the upper 30 cm of well-drained and moderately well-drained soils but did not occur below 20 cm in poorly drained soils. Poorly drained soils contained higher percentages of thrips in the upper 10 cm of the soil than did well-drained and moderately well-drained soils. These results suggest that estimates of thrips populations in the soil based on the number of thrips in samples collected from selected portions of the soil profile may need to be adjusted for soils of different drainage classes.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1118

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Studies were conducted in 1990 and 1991 to investigate the spatial distribution of counts of western corn rootworm,Diabrotica virgifera virgiferaLeConte, adults on yellow sticky traps in field corn. Samples were collected over 3 consecutive wk in July of each year using modified Pherocon A. M. traps placed in a 7 by 7 grid covering 0.84 ha in each of 24 cornfields. Dispersion indices indicated that counts of western corn rootworms on traps were aggregated. Geostatistic analyses, which are based on the relative position of samples, revealed that counts were nonrandomly distributed at least half the time at all population densities. Correlograms showed significant spatial relation in 46 of 72 trap-weeks (63%). Semivariograms, constructed from those 46 trap-weeks, were linear 55% of the time, suggesting the presence of gradients within the sampled portion of each field. The presence and type of spatial pattern was not correlated with mean density. Traps should be placed>30 m apart to obtain counts that are spatially independent.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1124

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We measured the feeding rate of the striped earwig,Labidura riparia(Pallas) on third-instar fall armyworm,Spodoptera frugiperda(J. E. Smith), at three constant temperatures and at three humidities. Striped earwigs ate more larvae at 30°C than at 25 or 35°C. Humidity did not affect feeding rate. Rogers' random predator equation described the effects of prey density on feeding at 30°C and 80% RH. Search rates were ≍1,127 and 4,355 cm2/d, and handling rates were 20 and 22.1 prey per day for males and females, respectively. Females consumed more prey than males. The striped earwig appears to bean excellent biological control agent for arthropod pests in row crops.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1134

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The nuclear polyhedrosis virus (AfMNPV)isolated from the celery looper,Anagrapha falcifera(Kirby), was tested against six species of production and postharvest lepidopteran pests and four insect cell lines. LC50s in PIB/mm2were 23.9, 42.2, 47.3, and 510.4, respectively, for raisin moth,Cadra figulilella(Gregson), navel orangeworm,Amyelois transitella(Walker), codling moth,Cydia pomonella(L.), and Indianmeal moth,Plodia interpunctella(Hübner). The almond moth,Cadra cautella(Walker), and the tobacco moth,Ephestia elutella(Hübner), were not susceptible. Histological examination revealed that hypodermis, fat body, tracheal matrix, midgut epithelium, and Malpighian tubules in all four susceptible species were infected. TheTrichoplusia nicell line TN368 and theP. interpunctellacell line PID2 were permissive to AfMNPV as well as to a contaminant cytoplasmic polyhedrosis virus (CPV). However, two navel orangeworm celllines, ATIO and AT20, were permissive to the CPV only. Restriction endonuclease analysis showed that the NPV was unchanged after passage through all of these hosts. Probably of greatest significance is that AfMNPV is the first baculovirus reported to be infectious to the navel orangeworm, a major pest of almonds.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1140

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

During July 1985 to June 1986, we surveyed the arthropod fauna associated withPistia stratiotesL., waterlettuce, in Florida. Plant samples were collected at 61 sites. Samples comprised a minimum of 20 waterlettuce rosettes. Invertebrates were removed from the plant sample using a submergence technique. Eighteen phytophagous species were recovered fromP. stratiotes. Six of these species are known waterlettuce feeders. They include the mothsPetrophila drumalis(Dyar),Synclita obliteralis(Walker), andSamea multiplicalisGuenée, the aphidRhopalosiphum nymphaeaeL., the leafhopperDraeculacephala inscriptaVan Duzee, and the weevilTanysphyrus lemnae(F.). Most of these insects are either stenophagous or polyphagous; none feed exclusively on waterlettuce. The paucity of specialists on waterlettuce in Florida contrasts sharply with the richness of oligophagous species in South America. This suggests that water lettuce is not a native species, despite observations of its occurrence in Florida as early as the mid-1700s.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1146

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Studies were conducted on rangeland in southwestern Idaho to evaluate the effect of moist, swalelike habitats on infectivity of an entomogenous fungus on two species of rangeland grasshoppers,Melanoplus bivittatus(Say) andMelanoplus sanguinipes(F.). Data clearly indicated that a significantly higher number ofM. bivittatuscollected from within the boundaries of four of five swale sites died from infection byEntomophaga calopteni(Bessey) Humber compared with infection levels among grasshoppers collected outside the swale margins. However, the incidence of infection ofM. bivitattusandM. sanguinipesdiffered significantly irrespective of location in or out of the swales. Disease incidence amongM. bivittatus, which was relatively abundant in moist habitats characterized by more succulent plant growth, was significantly higher. Results indicate that swales and other habitats that include a permanent or temporary free water component may support disease among some species of resident grasshoppers and thus serve as reservoirs of disease activity when weather conditions do not favor a widespread epizootic ofE. calopteni.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1156

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The purpose of this research was to determine the effect of the size of the host,Anthonomus grandis grandisBoheman, on adult size, sex ratio, longevity, and fecundity of the ectoparasitoidBracon mellitorSay. Adult size ofB. mellitorwas directly related to host size; larger parasitoids developed on larger host larvae. Host size also affected sex ratio so that predominately male wasps were produced on small hosts. The male bias on smaller hosts was caused by differential oviposition of male and female eggs by adult females. Female longevity and fecundity were directly related to adult size; larger females lived longer and subsequently produced greater numbers of progeny than smaller females.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1161

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Laboratory assays were conducted to determine effect of host plant on mortality of the southern corn rootworm,Diabrotica undecimpunctata howardiBarber, from the entomopathogenic nematodesSteinemema carpocapsaeWeiser andHeterorhabditis bacteriophoraPoinar and on nematode progeny production. Mortality ofD. u. howardi, as well as nematode progeny production, varied according to the host plant on which the rootworms had fed. Mortality fromS. carpocapsaewas lower for rootworms that had fed on peanut roots than for rootworms that had fed on squash or com roots. Mortality fromH. bacteriophorawas lower for rootworms that had been reared on corn roots than for rootworms that had fed on peanut or squash roots. For both nematodes, progeny production from larvae that had fed on squash roots was significantly lower than progeny production from rootworms that had fed on com or peanut roots. Host plant effects involving entomopathogenic nematodes and a soil-inhabiting stage of an insect pest have not been previously demonstrated.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1166

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

A virulent fungal pathogen,Entomophaga maimaigaHumber, Shimazu&Soper, was discovered in gypsy moth,Lymantria dispar(L.), populations across northeastern North America in 1989. It had never before been reported from North America, but many reports have documented the importance of this natural enemy in Japanese gypsy moth populations. We conducted experiments to estimate parameters for several components of theE. maimaiga/L. disparsystem, and an object-oriented simulation model was used to evaluate the dynamics of this system. Studies conducted with a 1984 Japanese isolate ofE. maimaigaformed the basis for this model. Successful infection by conidia required a median time of 8.69 h at 25°C. Data for period of lethal infection demonstrated that this pathogen cannot develop at30°C, and that mortality is high across all instars. Transmission experiments using caged saplings in the field were used to estimate a value for the proportion of conidia that successfully reach hosts and cause infection. Experiments with the model demonstrated results consistent with the existence of a host density threshold below which the rapid increase in secondary infection characteristic of epizootics does not occur. Primary infections throughout the field season were important in producing an adequate level of secondary inoculum for development of epizootics. Instar-specific larval behaviors were hypothesized as resulting in differential instar exposure to primary inoculum; inclusion of behavior-specific coefficients resulted in disease phenology more similar to observed patterns in the field. The model was also successfully tested using weather data from sites and dates when epizootics caused byE. maimaigawere known either to occur or not to occur. Variability in weather conditions across a larger geographic area caused heterogeneity in development of epizootics.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1172

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Leaf-miningLiriomyzaspp. and their associated hymenopterous parasitoids were surveyed during the fall of 1980 and spring of 1981 on fresh market tomatoes in west-central Florida.L. sativaeBlanchard was more abundant thanL. tnfolii(Burgess) in both seasons, accounting for 85.7 and 54.3% of the total reared in 1980 and 1981, respectively. The parasitoidsDiglyphus intermedius(Girault),D. begini(Ashmead), andNeochrysocharis punctiventris(Crawford) were the most abundant larval parasitoids reared from leafminer-infested foliage, accounting for 28.8, 26.3, and 15.6%, respectively.D. beginiwas not detected in 1980, but was nearly as abundant asD. intermediusin 1981.Opius dissitus(Muesebeck) was the most abundant larval-pupal parasitoid reared from leafminer-infested foliage, accounting for 51.8 and 12.6% of the total parasitoids reared in 1980 and 1981, respectively.

ISSN:1754-5692    

DOI:10.1093/ee/22.5.1188

出版商:Oxford University Press    

年代:1993

数据来源: OUP