摘要:

We propose a hypothesis that southern pine forests, the southern pine beetle,Dendroctonus frontalisZimmermann (Coleoptera: Scolytidae), and fire interacted historically within the geoclimatic regime of the Coastal Plain to maintain the structure and function of the southeastern coniferous forest. Fire regulates the regeneration in space and time of pine forests necessary forD. frontalisoccurrence;D. frontalisregulates the occurrence and turnover of patches of dead trees conducive to burning and windthrow. This interaction led to high community diversity and productivity, enabling these forested ecosystems to reduce nutrient losses and to respond rapidly to disturbance. Current silvicultural practices have disrupted these interactions and created forests particularly susceptible toD. frontalis. Applications of our hypothesis to development of forest management practices are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.821

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Among the species of the genusDiabroticathat occupy the United States, voltinism and adult collection sites are closely related to the presence of suitable larval hosts; thus, species in thefucatagroup are multivoltine polyphags and species in thevirgiferagroup are univoltine oligophags (or monophags). The group-specific differences in voltinism are attributed directly to the seasonal availability of the host plant and only indirectly to the climate.In thevirgiferagroup, univoltinism combined with a narrow larval host range and limited search capability suggest that oviposition behavior is the primary determinant of whether the newly hatched larvae reach a suitable host. Review of the biosystematic, archaeological, and historical records indicates thatD. virgiferasensu lato andD. l. barberiSmith and Lawrence have become pests of corn by convergent evolutlon. This evolutionary view suggests new avenues of research that are discussed in the text

ISSN:1754-5692    

DOI:10.1093/ee/10.6.826

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Traps baited with 30–50 female equivalents of natural female pheromones were tested for efficiency in capturing lab-cultured male olive fruit flies during the 1979 olive growing season. Densities of 2, 1, 0.5 and 0.266 traps/tree were tested; the average percent of fly recovery was 57.2, 40.1, 36.7 and 20.7, respectively. A single trap in an olive tree attracts males of that tree and neighboring trees, provided that no other pheromone traps are present. Flies of a tree with a trap do not respond to traps of neighboring trees. Male response to pheromone traps decreases with increasing distance. A trap density of 0.5 trap/tree throughout the experimental field and one trap/tree in the periphery is proposed for mass trapping tests with this pest.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.832

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Sequential decision plans based on the binomial distribution were developed for categorizing soybean defoliation caused by the Mexican bean beetle,Epilachna varivestisMulsant. Plants were classified as economically damaged if defoliation was ≥20%. Four plans were tested and compared by simulation on field data consisting of a fixed sample size. The plans showed an overall time saving of 31 to 68% and agreed with the fixed sample outcome in 82 to 91% of the simulations. Procedures that demonstrate the use of sequential decision sampling for soybean defoliation are given, and their application to field situations different from those in the study is discussed.The spatial distribution of within-plant defoliation was characterized and related to soybean growth and the population dynamics of the Mexican bean beetle. The vertical and horizontal distribution of both defoliation and leaf area changed significantly as the soybean plant matured and the overall level of damage increased. The possibility of biased estimates of defoliation, when subsampling plants, is discussed. Variance components at the field, plant, node, trifoliolate, and leaflet levels of sampling also were characterized. Half of the total variance in defoliation per leaflet was attributed to the trifoliolate position on a branch, whereas only 6.4% was due to variation among main stem nodes.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.835

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Gallery starts by the mountain pine beetle,Dendroctonus ponderosaeHopkins, were observed during aggregation on lodgepole pine,Pinus contortaDougl. Two phases of gallery initiation were identified: acceleration and deceleration. The acceleration phase is characterized by an increasing rate of gallery initiation and was highly variable in the trees sampled. The deceleration phase is characterized by a decreasing rate of gallery initiation and was significantly and linearly correlated with cumulative gallery starts a day or more old (r = −0.24). Transformation of the data to adjust for variation between trees increased the correlation between the deceleration rate and cumulative gallery starts a day or more old to −0.97. The resulting improvement in correlation suggests that variation in mountain pine beetle attack rates between trees can be attributed primarily to host factors. A linear model of gallery initiation during aggregation is presented.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.842

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Population density, dispersion, and dispersal were determined for the adult carabids,Pterostichus chalcitesSay,Scarites substriatusHaldeman, andHarpalus pennsylvanicusDeGeer, inhabiting an Iowa cornfield during the summer of 1975. Population density estimates were calculated by a mark and recapture technique. Maximum population densities forP. chalcites,S. substriatus, andH. pennsylvanicuswere 0.20 · m−2, 0.08 · m−2, and 0.39 · m−2, respectively. All three species had aggregated dispersion patterns, which were probably due to differences in the environment. Dispersal forP. chalcitesandS. substriatusaveraged 8.5 and 12.2 m/day, respectively, and individuals of these species were captured an average of 14 days after initial release.H. pennsylvanicusmay have dispersed more readily than the other two species and evidently moved into the field from field borders during early to mid-August.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.847

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Stator chihuahua, S. limbatus, S. pruininus, S. pygidialis, S. sordidus, andS. vachelliaeare all continuously breeding, noneconomic species. To determine reasons for their host preferences, these species were cultured in the laboratory, then presented with nonhost seeds, most of which were hosts for other species ofStatorused in the study.S. limbatus, S. pruininus, andS. sordidusoviposited on a wide range of hosts, butS. vachelliaewas very selective in the quality of seeds that it oviposited upon, and it completed development in only two nonhosts.S. limbatus, S. pruininusandS. sordiduscompleted their development in 3, 9, and 20 nonhost seeds, respectively.S. sordidus, which has only three natural hosts, is unique in being able to survive in so many non host seeds. The seed coats ofCercidium floridum, Parkinsonia aculeata, and some other plants are formidable barriers to the entry ofStatorspp. Possible reasons for host preferences inStatorare given.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.857

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Colonization cages were filled with organism-free, standardized, stone substrate and placed in the stream bed above and below the effluent from an inactive lead and zinc mine in western Colorado. A significantly higher proportion of the total individuals colonizing cages from an upstream direction were dead below the effluent compared with the controls above the effluent. The percent “mortality” of the mayfly,Baetis bicaudatus, the dominant species in Coal Creek, was also consistently higher below the effluent. Total numbers of live insects colonizing cages were generally higher above the effluent; but results were not as consistent as “mortality” data. A diversity index (H'), species richness, and equitability (J') of the samplers were not reliable indices of responses to stress by the benthic community. Given cages with contaminated substrate in uncontaminated water, the community recovered remarkably quickly. Colonizing populations were indistinguishable from those of control cages with uncontaminated substrate within 9 days. We conclude that the substrate habitat below the mine effluent is unsuitable for most benthic invertebrates and that the colonization technique that allows determination of percent mortality is more consistent and reliable than conventional measures of diversity for assessing the response of benthic invertebrates to stress. If water quality can be restored to a pristine state, the benthos may rapidly recover from the effects of previous acid mine drainage stress.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.864

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

The interaction between bollworm and boll weevil and cotton development has been assessed under the climatic conditions of Nicaragua. The ratio of the rate of fruit point production to the rate of cumulative fruit damage (βT/β2) has been used to assess final yields in treated and untreated fields. An economic decision rule for pesticide applications was developed from these data.

ISSN:1754-5692    

DOI:10.1093/ee/10.6.872

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Effects of soybean,Glycine max(L.) cv. Bragg, phenology on leaf consumption and development of the velvetbean caterpillar (VBC),Anticarsia gemmatalisHübner, were investigated at 26.7 ± 1° C, 14L:10D photoperiod, and RH>80%. Soybean plant stages were designated as early vegetative (V2–V5), late vegetative (V5–V8), flowering (R1–R2), pod set to pod fill (R4–R6), and senescent (R7–R8).Mean leaf fresh weight consumed by 4th- and 5th-instar VBC larvae declined as plant phenology progressed. Dry-weight consumption did not tend to decline with plant phenology and was more uniform for all plant growth stages than the freshweight values. Mean larval development time varied from 12.6 to 14.3 days, and mean time from egg hatch to adult varied from 21.9 to 23.4 days when larvae were fed late-vegatative and senescent foliage, respectively. Larvae fed senescent leaves produced pupae with reduced weight. Sex ratio (male/female) varied from 0.83 (flowering stage) to 1.37 (late-vegetative stage).

ISSN:1754-5692    

DOI:10.1093/ee/10.6.880

出版商:Oxford University Press    

年代:1981

数据来源: OUP