摘要:

Microplitis croceipes(Cresson) andCotesia(=Apantales) marginiventris(Cresson) produced inHeliothis zea(Boddie) larvae infected withVairimorphasp. were compared with parasitoids produced in uninfected larvae. The criteria used for comparison were: percentage of hosts producing parasitoids, developmental time, longevity, and infection by the microsporidium. There was no significant difference in productivity of parasitoids in infected and control larvae. There was a small, though statistically significant, increase in the developmental time ofM. croceipesreared in infected larvae. The number of parasitoids infected byVairimorphawhen produced in infected larvae was not significant. Transmission ofVairimorphaby parasitoids produced in infected larvae was not significant; however,M. croceipesfemales which were exposed to infected larvae for oviposition transmitted the pathogen to a significant number of subsequent larvae.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1547

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Adult activity and reproductive condition of the green cloverworm (GCW) were monitored in soybeans during 2 outbreak years (1978 and 1979) and 2 endemic years (1980 and 1981). Although four adult flights may occur in any year, adult phenology was substantially different between the two types of years. Furthermore, flights 1 and 4 may be too small to be detected in endemic and outbreak years, respectively. Regardless of the type of year, no females captured during flights 1 and 2 were unmated and preovipositional. It is suggested that both flights are composed of immigrating adults and that flight 1 moths do not directly give rise to flight 2 moths in Iowa. Adult activity also was monitored during 1979 and 1980 in alfalfa, which is the primary alternate host of GCW in central Iowa. The same flights were observed in both crops, but relative abundance and the proportion of unmated females were lower in alfalfa than in soybeans. These results imply that survivorship and adult emergence are lower in alfalfa. The most likely cause of reduced adult emergence in alfalfa probably is the frequent cutting of the crop for hay production. Consequently, alfalfa fields probably serve as population sinks for GCW, with populations in alfalfa contributing relatively little to populations in soybeans. These results are combined into a hypothesis to explain GCW population dynamics in central Iowa.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1551

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

About 7 kg of honey bees were caged, stored for 2 days, and subdivided into 3 populations: ca. 4,400, 8,900, and 34,000 bees. The bees then were placed in hives that had no brood and a known quantity of honey. The resulting colonies had ca. 2 liters of space and one caged queen per 1,000 bees. Worker survival, honey loss per bee, colony temperature, and survival of caged queens were compared in six replicates. Each replicate covered 20 to 27 days during winter in Baton Rouge, La. Population size had no effect on survival of workers or caged queens. However, larger populations were significantly warmer than smaller populations when the ambient temperature was<13°C (P<0.05). Honey loss per bee per day was significantly greater for 4,400 bees (mean ± SD = 6.7 ± 1.5 mg) than for 8,900 (4.5 ± 1.7 mg) or 34,000 (4.2 ± 0.7 mg) bees (P<0.05).

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1559

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Population densities of the bean leaf beetle (BLB),Cerotoma trifurcata(Forster), and the portion of the BLB population transmitting bean pod mottle virus (BPMV) were monitored in a soybean field in Lafayette County, Ark., in 1980 and 1981. The spatial and temporal distribution of BPMV-infected soybean plants in two plots within the field also was examined. A peak in the BLB's ability to transmit BPMV occurred between the second and third population density peaks and ca. 12 weeks after planting. The largest increase of BPMV infection level within the plots occurred after the second BLB density peak in the field. Distribution of BPMV-infected plants within the plots was random at infection levels of40%.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1564

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

During early season,Geocoris punctipes(Say),Hippodamia convergensGuérin-Méneville, andColeomegilla maculataDeGeer were found primarily on cotton plant terminals. During mid and late season, populations were found to be 7 to 8 nodes below plant terminals. After fruiting structures were formed, mostH. convergensand a large percentage ofG. punctipeswere found between fruit and bracts.C. maculataalso tended to concentrate on fruit, but to a lesser extent than the other species. Population estimates obtained with a vacuum sampler were only slightly lower than estimates based on whole-plant visual searches when predators were primarily on plant terminals. Estimates based on vacuum samples were much lower, however, when insect populations were found primarily between bracts and fruits.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1568

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Fungicide applications were made during apple,Malus domesticaBorkch., bloom to determine the duration of fungicide effects on pollen viability in the field and whether spray applications affect the foraging behavior of honey bees.Apis melliferaL. Fungicide sprays did not affect the numbers of honey bees foraging on trees or their foraging behavior. Mean percent pollen germination was depressed to levels between 12.2 and 31.1% by captan and to 29.5% by Dikar 2 h after spray application. Recovery of pollen viability required 24 to 48 h, depending upon orchard conditions. Benlate, Polyram, Baycor, and Topsin-M had no significant effect on pollen viability. The rapid recovery of pollen viability after initial spray applications and the lack of effect on flower visitation by bees indicate minimal effects on pollination or fruit set under most conditions.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1572

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Caged ‘Concord’ grapevines were artificially infested with “low” and “high” populations of the leafhopper,Erythroneura comesSay, between early July and late August from 1979 to 1982. Foliage injury became evident shortly after the first introductions and increased during the season. At harvest, the injury inflicted by the “high” populations in the caged vines was similar to or higher than the injury inflicted by natural populations ofE. comesin commercial vineyards. The caged grapevines injured byE. comesproduced fruit yields and juice quality that did not differ significantly from the noninfested caged vines. In addition, vine vigor was not reduced by the leafhopper injury. Concord vines may be able to withstand greater injury from first- and second-generationE. comesthan was previously believed. Lacking in this study was foliage injury that may occur during June from overwintered leafhoppers as they first enter vineyards. This is the main period of berry and cluster primordia initiation, the major contributing factors to fruit production.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1576

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Various sampling schemes were evaluated for estimating the population size of the apple aphid,Aphis pomiDeGeer, on an apple tree. More aphids were found to inhabit the actively growing shoots in the top of the tree canopy than the bottom. An average of 90% of the total aphid population occurred on the first six leaves at the top of the tree, whereas the first four leaves contained 90% of the aphids at the bottom for all sampling dates. The method of counting the number of aphids on the most infested leaf provided the most accurate assessment of aphid density, but it required the most effort. Counting only the number of infested leaves per shoot resulted in a decrease in accuracy, but also a 4- to 8-fold decrease in the time required to sample. Reliable estimates of the aphid population over an entire tree can be made from sampling only those areas of the tree reachable from the ground. Sample size estimates are presented on the number of shoots and trees to sample, as well as an estimate of precision.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1581

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Individual females ofTrichogramma nubilaleErtle and Davis were exposed to various densities (1 to 12) of European corn borer (ECB),ostrinia nubilalis(Hübner), egg masses for different exposure periods (l to 120 h). This parasitoid avoided excessive superparasitism under every host density and exposure period tested. It appears that the ovipositional behavior and manner of progeny distribution ofT. nubilalefemales are uniquely adapted to the mode of egg laying by its natural host, the ECB.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1587

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Douglas-fir tussock moth egg masses were found throughout the foliar portions of the crowns of 12-m Douglas-fir trees, but there was a trend to higher density in the upper crown. In 1-min visual surveys taken before trees were sampled in detail, 11% of the total egg masses present on the trees were observed.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1590

出版商:Oxford University Press    

年代:1983

数据来源: OUP