摘要:

To improve our understanding of factors that affect intraplant distribution ofArtogeia rapae(L.) andTrichoplusia ni(Hübner) on cabbage, we exposed larvae to gradients of cabbage leaf age. Excised leaves from field-grown cabbage were arranged in a chamber to form the gradient of leaf age. Larvae in the third-fifth instar were allowed to feed on these leaves for 48 h, and leaf area consumed was measured. Larvae ofT. nishowed no preference for leaves of any particular age, eliminating one of a number of factors that were suspected of affecting their distribution on cabbage. Larvae ofA. rapaepreferred the youngest (head and wrapper) leaves, which helps explain observed intraplant distributions on these larvae in the field and allows us to predict the location of their feeding damage on the plant.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.680

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Influence of temperature on the development and hatching of eggs ofSimulium arcticumMalloch IIS-10.11 was determined. Temperature-dependent development and hatching at six constant temperatures are described. The rate of egg development was greatest at 18°C. The data fitted a six-parameter development model. Linear regression of the development rate versus temperature provided estimates of base temperature and development time in degree-days for 50 and 90% hatching of eggs. Results are compared with reports on egg hatching and larval distribution ofS. arcticumsensu lato in Alberta, Canada.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.683

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Seasonal patterns ofLygus hesperusKnight abundance and distribution were observed at two conifer nurseries in western Oregon during 1985.Lygusabundance differed significantly among conifer seedling types (age class/species combinations) and sampling dates. Highest densities were observed in lodgepole pine and ponderosa pine seedlings germinated during 1985, in Douglas-fir seedlings germinated in 1984 and in late July samples. Significant interaction between seedling type and sample date reflected a shift inLygusoccurrence among seedling types during the growing season, especially from 1984 Douglas-fir seedlings early in the season to 1985 seedlings later in the season. This shift coincided with dispersal of the firstLygusgeneration and with pruning of the 1984 seedlings for height control. These results indicate thatL. hesperusabundance and distribution in conifer nurseries result fromLygusphenology in combination with seasonal changes in the spatial pattern of available resources. Implications for nursery management are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.687

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Transmission of nuclear polyhedrosis virus (AgNPV) in uniform- and mixed-aged populations of velvetbean caterpillar (VBC),Anticarsia gemmatalisHübner, larvae artificially established on field-caged soybeans was examined. In a uniform-aged VBC population, transmission of AgNPV from primary infected to uninfected VBC was generally low. Larval mortality from AgNPV was highest in treatments with highest density of primary infected larvae, but did not differ with size at death of primary infected larvae. Transmission in mixed-age populations was greater than in uniform-aged populations when primary infected larvae were of the same age structure as the uninfected population or all the age of the oldest uninfected larvae in the population. Virus concentration on foliage after pupation of survivors in both uniform- and mixed-aged populations was high, but little viral activity remained on foliage 1 mo later. Virus concentrations in soil in both tests were generally low immediately after pupation but were much higher 1 mo later.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.691

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Dispersion patterns of eggs and larvae of the weevilNeochetina eichhorniaeWarner within waterhyacinth shoots were examined in two field studies. In whole-plant dissections, eggs were rarely found in the youngest, uppermost leaves but were common in mature leaves. Late instars occurred more frequently in older leaves, usually concentrated in the basal portion of the petiole. As instar increased, increasing proportions occurred within the stem (rhizome). In a second study, plants were first grown in small pools for varying durations, then transplanted to a field site. Leaf age accounted for 83% of among age-class variation in average number of eggs per leaf, and more eggs were found in older leaves. Time in the field accounted for 89% of variation in average number of larvae per leaf when standardized to percentages of the total found at each harvest. Dispersion of eggs seemed to be influenced by leaf age but dispersion of larvae was strongly influenced by exposure duration. Selection of leaves for oviposition by female weevils may be based upon distribution of secondary metabolic compounds or nutrients, or both. Leaf senescense and ultimate sloughing of the leaf from the shoot could be a significant source of mortality to eggs and possibly larvae. Ontogeny and leaf dynamics are important driving forces in dispersion of the relatively immobile insects within waterhyacinth shoots. Third instars, however, seem able to move easily within the shoot and are less affected by leaf dynamics. Movement by larvae to petiole bases probably maximizes their chances of staying with the shoot if the leaf detaches.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.699

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Resistance to alfalfa weevil (AW),Hypera postica(Gyllenhal), detected inMedicago sativaL. has been primarily tolerance to feeding of the larvae. Adult feeding resistance has been found in glandular-haired annualMedicagospecies, but these cannot be hybridized with alfalfa to produce useful cultivars. In this study, two diploid (Medicago glandulosaDavid andMedicago prostrataJacquin) and one tetraploid (Medicago glutinosaMarshall Von Bieberstein) glandular-haired, perennial species were tested for resistance to AW adult feeding. Control plants were perennialM. sativa(susceptible) and annualsMedicago scutellata(L.) Mill andMedicago disciformisDC (resistant). Dry-matter consumption, leaf damage ratings, and numbers of AW on the entries were all lower forM. prostrataandM. glandulosathan for susceptibleM. sativa.M. glutinosadid not seem to be consistently resistant to adult AW feeding.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.708

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Bark of mature Fraser fir,Abies fraseri(Pursh.) Poir, from Mt. Mitchell, N.C., and Mt. Rogers, Va., was artificially wounded and treated with chemicals (naphthalene acetic acid, pectinase, or todomatsuic acid) suspected to be in association with balsam woolly adelgid,Adelges piceae(Ratzeburg), attack. α-and β-pinene, δ-3-carene, and limonene were the only monoterpenes found in Fraser fir at both locations. There were no differences in monoterpene content between wounds and controls at either site, but bark samples from firs at Mt. Rogers contained lower percentages of α-pinene and δ-3-carene than firs at Mt. Mitchell. Sapwood tissue beneath adelgid wool masses at the above sites and Roan Mt. were also analyzed for monoterpenes. Infested trees at Mt. Rogers contained less α and β-pinene than uninfested controls. There were no differences at Mt. Mitchell or Roan Mt.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.712

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Two enclosed, shallow-pit, egg-layer poultry houses in north-central Indiana were sampled to determine densities and parasitism of house fly (HF),Musca domesticaL., pupae during 1982 and 1983. Seven parasitoid species emerged from sampled pupae:Spalangia cameroniPerkins,Spalangia nigroaeneaCurtis,Spalangia endiusWalker,Spalangia nigraLatreille,Muscidifurax raptorGirault&Sanders,Nasonia vitripennis(Walker) (Hymenoptera: Pteromalidae), andAphaereta pallipesSay (Hymenoptera: Braconidae).S. cameroniwas the most abundant species, emerging from 78.8% of all parasitized pupae collected, and also was the only species collected during winter. Although HF pupae were relatively abundant during winter, active parasitism was not observed during late winter and spring months. A positive relationship between parasitism and nonviability of parasitized pupae suggested that host feeding by parasitoid adults may substantially contribute to HF mortality. Possible strategies to suppress densities of HF pupae by periodically releasing parasitoids are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.716

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Major differences occurred in the physical and chemical parameters of three dung types, NGD, MGD, and HGD, from cattle fed diets containing no grain, and medium (35–40%), and high (>60%) amounts of grain, respectively. Both NGD and MGD differed from HGD in a majority of the parameters measured over a 3-d period, including face fly,Musca autumnalisDe Geer, larva survival to the pupal stage, production of large quantities of organic acids in HGD, substantial decreases in pH of>1 pH unit, and large increases in osmolality (ca. 200 mmol/kg) in HGD. Alteration experiments indicated that a complex of factors causes the increase in larva mortality associated with HGD, including low pH, elevated osmolality, and the production of organic acids such as volatile fatty acids and lactic acid.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.722

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Distribution and movement of marked oriental cockroaches,Blatta orientalisL., were studied at four apartment buildings during the summers of 1984 and 1985. Porches were the primary cockroach harborage sites during the summer. In a mark/recapture study, 50% of marked, resighted cockroaches remained at one porch, 35% moved within an area on one side of a building, 13% moved between the front and back of a building, and 2% moved between buildings. Only 2% of these resighted cockroaches moved indoors.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.731

出版商:Oxford University Press    

年代:1987

数据来源: OUP