摘要:

Periodic mass rearing and harvesting of specific life stages are analyzed based on the theories of both the age-specific life table and the age-stage, two-sex life table. Formulae for the calculations of the optimal discard age and harvest rate are derived. For practical applications, the use of thermal summation to manipulate the developmental time of specific life stage is suggested. The model is demonstrated using life table data ofOstrinia furnacalis(Guenée).

ISSN:0046-225X    

DOI:10.1093/ee/23.3.535

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Because the measurement of insect mortality caused by parasites and disease is fundamental to biological control and related fields, accurate data are of great importance. Most studies rely on the rearing of hosts to determine the incidence of disease and parasitism, and the results are seldom compared with those determined by the dissection method. The examples in the current study show that parasitism measured by dissection was 12 to 44% higher than by rearing, and that dissections are much more accurate than rearing for measuring the effects of parasites and disease, because dissection data are not confounded by the disproportional mortality of parasitized hosts by disease and stress that occurs during the rearing process. Moreover, even parasitism data obtained by dissections underestimate mortality because a considerable proportion of hosts die of oviposition trauma, and in some species, after being fed upon by female parasites before they are sampled. The rearing method is useful for determining parasite species as well as other purposes, and these are listed along with the numerous advantages of dissections. Although dissections provide the most accurate mortality estimates, for the most comprehensive results, both rearing and dissection methods should be used concurrently.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.543

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The dispersion pattern ofContarinia sorghicolaCoquillet was explored by analyzing the distribution of captures along transects in grain sorghum plots. Adhesive traps at different distances from the edges of the plots were used to intercept dispersing midges. Mortality rates were determined experimentally. A passive diffusion model was fitted to the distribution of captures and the diffusion coefficient estimated. The passive diffusion model gave a good approximation to the spatial distribution of midges dispersing in sorghum plots. The estimated diffusion coefficient suggests that females disperses at a rate of 90 m2/h in sorghum plots. The model is used to predict the spatio-temporal distribution of midges dispersing inward from the edges of plots and identify areas susceptible to midge attack.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.551

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

We attempted to develop an accurate and efficient means to estimate gypsy moth egg mass density or, alternatively, develop techniques to aid in prioritizing areas that might require egg mass sampling. Results indicate that it is possible to determine the probability of finding some level of egg mass density in the vicinity of a pheromone trap depending on the number of moths captured in that trap. A linear relationship was found between number of moths captured and gypsy moth egg mass density, but this relationship has little predictive value. Wing length of male moths collected in pheromone traps was used to estimate defoliation and male moth dispersal. Wing length of moths captured in pheromone traps was found not to be a reliable indicator of whether or not defoliation occurred. However, capture of small moths, which develop in defoliated areas, in traps located in nondefoliated areas indicated that these moths probably dispersed from other, defoliated areas. Capture of small moths may be useful to determine whether or not to initiate egg mass sampling at the trap location. An algorithm to interpret data from pheromone traps is presented. Trap data interpretation involves use of male wing length, number of moths captured, and defoliation maps. The information obtained from the algorithm will be most useful to evaluate an area for the need to conduct egg mass sampling. Forest managers can evaluate the risk of failing to detect high egg mass density with the need to allocate sampling resources optimally.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.556

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Pollen on corn earworm moths,Helicoverpa zea(Boddie), can provide an indication of their host plant visitations and migratory activities. Our study was conducted to determine the origin ofCitrussp. pollen-contaminated moths captured in Atoka County, Oklahoma, during 1990 and the host plant feeding range of moths present in Hidalgo County, Texas, and Atoka County. Captured moths were analyzed for pollen with scanning electron microscopy.H. zeamoths captured in January 1989 in the Lower Rio Grande Valley of Texas when citrus was not blooming were not contaminated withCitrusspp. pollen. Sixty percent of those captured on 17 March 1989 during the citrus blooming period were contaminated withCitrussp. pollen. None of the moths sampled in that area between 21 March and 2 April 1990 were contaminated withCitrusspp. after a major freeze in December 1989. Citrus blooming during 1990 was drastically reduced or eliminated in South Texas, northeastern Mexico, Louisiana, and central Florida. However,Citrussp. pollen accounted for 3% of all pollen detected on migratoryH. zeacollected in Atoka County between 27 February and 24 April 1990. Lack ofCitrusspp. pollen-contaminatedH. zeain Hidalgo County after the severe freeze suggests theH. zeacontaminated withCitruspollen was collected in Atoka County during April 1990 originated elsewhere. Evaluation of calculated trajectories, synoptic weather maps, and upper-air transport opportunities suggests southern Florida, the Bahamas, Cuba, Yucatán Peninsula, and northern Central America as potential source areas 1,515 km from the capture site. This would require the moths to be in flight over water for 72 h or have very limited diurnal resting periods on seaweed (Sargassumspp.), ships, oil platforms, or the sea surface.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.562

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Many biotic and abiotic factors influence colonization and degradation of cattle dung pats. Thus, studies using the pat as an experimental unit require precise methodology to prevent misinterpretation of results. This paper reports trials in which impact of methodological procedures on dung fauna and dung degradation was investigated. Factors investigated were pat position on pasture, sampling techniques, influence of various diets, and a comparison between naturally voided versus artificially formed pats. Parameters used to measure these factors included quantitative and qualitative monitoring of dung fauna, including Coleoptera, Diptera, bacteria, nematodes, and Lumbricidae, and assays of pH, moisture content, and organic matter content of dung. An influence of pat position on colonization was seen, with Staphylinidae occurring more frequently in pats located toward the center of a pasture compared with pats located close to a road. Coleoptera larvae preferred the northern parts of the pats. Pat composition influenced colonization of Coleoptera. Staphylinidae and Scarabaeidae preferred pats from cattle fed with grass, but Hydrophilidae preferred pats from cattle fed corn silage. More Coleoptera larvae were collected from pats produced by grazing cattle compared with pats from cattle fed hay or corn silage. There were no significant differences between artificial and natural pats as to the total number of Coleoptera, Diptera, or bacteria collected. However, development of Diptera larvae was accelerated in the artificial pats. Degradation of pats measured by content of organic substance and pat area was similar in artificial and natural pats.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.571

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Factors involved in trap design, trap construction, and trapping protocol in the field were examined to determine their influence on accuracy of an established monitoring program for the carrot rust fly,Psila rosae(F.). Changing the adhesive from Stikem Special to Stiky Stuff did not alter trap efficacy significantly. Catches ofP. rosaedecreased linearly with decreased trap surface area, but reducing coverage of standard-sized traps coated with adhesive by up to 75% did not alter trap efficacy significantly. Lengthening trap inspections from 4 d to 7 or 10 d would have underestimated counts of flies on traps, leading to omissions or delays in spray recommendations. Traps situated near outer perimeters of fields generally captured more flies than traps placed inside fields. This trend was sometimes reversed when crops were young, and catches were equal on inner versus outer traps in a mature field late in the growing season. Traps placed at corners of fields generally captured more flies than those placed between corner traps along field perimeters. Traps coated on both north- and south-facing surfaces captured significantly more flies on the north face in all three flight periods. Based on the results, a modified monitoring program forP. rosaeis described that would be as effective, but more economical to operate than the existing program in British Columbia.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.579

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The distribution and host plant associations of the pear thrips,Taeniothrips inconsequens(Uzel), were determined from published and unpublished data.T. inconsequensis found throughout Europe and much of North America as well as in some countries of Asia and South America; there is one record from North Africa. It is generally considered thatT. inconseqyensis native to Europe, but we present good evidence to suggest that Asia is its area of origin. Breeding hosts forT. inconsequenswere identified from 35 species, 17 genera and 12 families, with incidental records from at least 207 species, 138 genera and 54 families. Breeding hosts were mainly from the Rosaceae (5 genera, 16 species) and Aceraceae (1, 7) but also members of other plant families. Incidental collections were mostly from the Rosaceae (15 genera, 36 species) but also members of a wide range of plant families including the Compositae (10, 12), the Leguminosae (10, 11) and the Aceraceae (1, 9). Reports of economic damage to orchard and forest trees are listed. There is no evidence to suggest that recent outbreaks ofT. inconsequensin northeastern hardwood forests of the United States and adjacent areas of Canada can be explained by recent changes in host plant preference.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.587

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Intraspecific and interspecific competition among northern corn rootworms,Diabrotica barberiSmith&Lawrence, and western corn rootworms,Diabrotica virgifera virgiferaLeConte, were investigated under greenhouse conditions. Densities of both species were varied on potted corn seedlings to determine the effects of competition on adult emergence. The results depended on the initial larval densities of the two species. Intraspecific and interspecific competition significantly affected in adult emergence of both species. Western corn rootworm adult emergence was influenced more by intraspecific competition than interspecific competition, but females were effected by northern corn rootworm densities. Northern corn rootworm was very sensitive to both intraspecific and interspecific competition.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.612

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Consumption of armyworm,Pseudaletia unipunctaHaworth, by generalist predators and the role of generalist predators in protecting corn plants from armyworm feeding damage were evaluated in laboratory feeding trials and in a predator-removal field study, respectively. Thirteen of the fifteen taxa evaluated in the laboratory feeding trials fed upon armyworm larvae. The highest consumption rates were exhibited by the carabidsPterostichus chalcitesSay,Pterostichus lucublandusSay, andScarites subterraneusF.; the staphylinid,Platydracus maculosusGravenhorst; and the lycosid,Lycosa helluoWalckenaer. The most common potential armyworm predators removed from the field with pitfall traps included ground beetles (Carabidae), rove beetles (Staphylinidae), ants (Formicidae), and spiders (Araneae). Armyworm damage to corn plants was significantly greater where generalist predators were removed using pitfall traps and exclusion arenas than in the control where predator populations were unaltered.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.617

出版商:Oxford University Press    

年代:1994

数据来源: OUP