摘要:

Seasonal population densities ofHeliothis virescens(F.) andH. zea(Boddie) in the Imperial Valley of California were determined by pheromone-baited trap catches and by egg and larval densities in alfalfa, cotton, and lettuce. Moth populations were present from March to December; low densities during winter and early summer corresponded to conditions favoring winter diapause and summer estivation, respectively. The relative importance of each host in supporting moth populations varied seasonally. The dominant species in alfalfa wasH. zea, whereasH. virescenswas dominant in cotton and lettuce. The highest population ofH. zeain alfalfa occurred in late spring and late summer, in cotton during early summer, and in lettuce during October. The highest populations ofH. virescensin alfalfa were found during October, in cotton from July through October, and in lettuce from October through December. Populations in alfalfa and cotton were greater in commercial fields than pesticide-free untreated fields, whereas lettuce populations were greater in untreated fields. Larval mortality from parasitoids and viruses was infrequent except in alfalfa during late spring and early summer.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.970

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Comparison of daily and seasonal values of whole-body lipid, ovarian development, and two mating parameters (percentage of mating and number of spermatophores) were examined in adult soybean loopers,Pseudoplusia includens(Walker). Laboratory moths had a greater percentage of whole-body lipids and numbers of chorionated eggs compared with field-collected 3-d-old moths. Females contained a significantly higher percentage of whole-body lipid than males. Late-season (November) females delayed chorionated egg maturation and had higher nonegg lipids than in summer (July, August, and September) and early fall (October) females. Both sexes contained a greater percentage of whole-body lipids late in the fall compared with early-season moths. There was no shift in the daily percentage of mating or number of matings between seasons. Thus, soybean loopers appear to exhibit some of the physiological characteristics associated with Johnson's oögenesis-flight syndrome proposed for migratory insects.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.980

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Within 1-ha plots, gypsy moth,Lymantria disparL., densities were artificially elevated from low densities (about 20 egg masses/ha) to high densities (8,000 egg masses/ ha) using field-collected eggs and F1sterile laboratory-reared eggs. At all sites, including the feral and sterile release areas, densities decreased to undetectable levels (less than 10 egg masses/ha). In the sterile and feral release areas, parasitism byCotesia melanoscela(Ratzeburg) was the largest source of identified mortality and was significantly greater than in the surrounding area or in untreated plots. Within the feral release area, parasitism byCompsilura concinnata(Meigen) andParasetigena silvestris(Robineau-Desvoidy) was substantial and was greater than in the surrounding area. This pattern was not observed in the sterile release area. This difference may have been caused by differences in gypsy moth phenologies between the two populations. Spatially density-dependent mortality caused by parasitoids is hypothesized to be important in the regulation of low-density populations. Furthermore, this mortality may have profound effects on attempts to suppress populations using releases of induced- inherited sterile insects.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.986

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The flight behavior ofListronotus bonariensis(Kuschel) in Waikato (New Zealand) pastures was studied by recording catches on aerial sticky traps and sampling ground populations; this was supported by dissection studies and laboratory experimentation. All flight activity in the field occurred between 25 August and 5 May. Flight phenology and intensity varied greatly between localities and years. Intensity was generally low, although occasional mass flights were observed. Sampled ground populations indicated that only a proportion of the weevils exhibited development of flight musculature and hence flight capability: the proportion of these “flight capable” weevils varied greatly from generation to generation. Field sampling and laboratory experimentation indicated partitioning of reproductive and dispersive effort among individuals in the population. Following emergence, some weevils became reproductive and others developed flight musculature before ovarian development and dispersal. The proportion of weevils in the latter category was highest in the field following peak emergence and was shown by laboratory experimentation to be increased by weevil crowding, particularly on unfavorable host plants. The laboratory experiments also indicated that alleviation of crowding resulted in degeneration of flight musculature and resumption of reproductive activity. Field sampling indicated overwintering in the pastures (summer breeding grounds) and no migration to adjacent potential hibernation sites. These results are discussed in relation to the climate of the Waikato and the dynamics of the populations.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.996

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Numbers of instars, weight gains, relative growth rate, relative consumption rate, and efficiency of conversion of ingested and digested food were measured for the velvetbean caterpillar,Anticarsia gemmatalisHübner, while feeding on six legume species: hairy indigo, lespedeza, soybean, sesbania, white sweetclover, and cowpea. Sesbania was the most suitable host; lespedeza the most unsuitable. Supernumerary instars were observed for larvae fed cowpea and lespedeza. Two other legumes, crotalaria and sicklepod, did not support complete larval development.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1006

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Larvae ofLonchaea corticisTaylor killed and consumed pupae and to a lesser extent prepupal larvae ofPissodes strobi(Peck) at temperatures ranging from 5 to l4°C during a 3-wk experiment in glass vials that were monitored weekly. Marginal predation of pupae but not prepupal larvae was observed at O°c. In simulated pupal cells ofP. strobistored outdoors in a Victoria, British Columbia, winter,L. corticislarvae killed and consumed pupae and prepupal larvae ofP. strobiin a 3-wk experiment that left most cells devoid of obvious prey remains. Tests in glass vials in March withL. corticislarvae collected during March and during the previous August showed thatL. corticislarvae remain predacious at the end of winter. When the insects were left in situ in severed leaders stored outdoors in a Victoria, British Columbia, winter, the proportion of pupal cells with liveP. strobidecreased significantly and the proportion of pupal cells emptied without insect emergence increased significantly; the numbers ofL. corticislarvae and totalP. strobipupal cells did not change significantly. These experiments show thatP. strobipupae and prepupal larvae can be vulnerable prey forL. corticislarvae and that predation may be common in the winter conditions of coastal British Columbia.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1011

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Changes in potato leafhopper,Empoasca fabae(Harris), stage distribution on potato and snap bean were examined in 1984–1985 with the objective of determining whether invasions were of local or long-distance origin.E. fabaepopulations were routinely sampled in potato and snap bean fields emerging after firstE. fabaearrival in Rosemount, Minn. (4 June in 1984,9 May in 1985,0 cumulative degree days [CDD], base 8.4°C). Adults were first consistently collected on potato and snap bean 325–475 CDD in 1984, and several large influxes occurred 355–494 CDD in 1985. These invasions occurred when first-generationE. fabaewould have matured on undisturbed hosts, suggesting they were of local origin. With the first large increase inE. fabaenumbers, there was a shift in sex ratio (data available for 1985 only) from predominantly female to 50:50. There is some evidence for dispersal following harvesting or plowing of alfalfa, but invasion correlated best with heat unit accumulations sufficient for the development of F1progeny.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1015

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Within-tree populations of the southern pine beetle,Dendroctonus frontalisZimmermann were examined in shortleaf pines,Pinus echinata(Mill.), with nylon mesh tents enclosing the portion of the bole where beetles were released. The distribution of the beetle population within the trees differed slightly from the distribution of beetles in naturally infested trees. However, the density, within-stage survival, and adult replacement rate were similar to measurements of these parameters in naturally infested trees. Also, the relationship between egg niche density and total parent gallery length was examined and found to be similar to previous reports. The tents protected the beetles from competing species; survivorship from egg to adult (33.5%) was high. It was concluded that the tents offer a reliable approach to examining the interactions betweenD. frontalisand its host pines. Possible uses of the tents for further studies on population dynamics and interspecific interactions are discussed.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1025

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The hourly foraging activity of honey bees,Apis melliferaL., was observed on guayule,Parthenium argentatumGray, during two years, at Tucson, Ariz. Foraging activity occurred from 0700 to 1800 hours (MST) and the maximum abundance of pollen collecting was at 1000 hours. The percentage of guayule pollen collected by honey bees at Marana, Ariz., ranged from 2 to 76%. Pollen collections during the month of May had the highest amount and percentage of guayule pollen. Guayule plots with bees produced twice as much seed as plots from which bees were excluded. These results indicate that honey bees visit the guayule flowers, collect pollen, assist in pollination, and effectively increase quantity and quality of seed.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1032

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Formulations ofBacillus thuringiensisBerliner spores and crystals, encapsulated together within a starch matrix containing no ultraviolet screens, lost all spore viability and insecticidal activity against the European corn borer,Ostrinia nubilalis(Hübner), within 4 d. Encapsulated crystals and spores with Congo red or folic acid as screens exhibited moderate spore viability and retained at least 50% of their original toxicity after 12 d. Congo red was the most effective protectant, followed by folic acid and para amino benzoic acid. BecauseBacillus thuringiensisis likely sensitive to the entire ultraviolet-component in sunlight, ability to provide broad-band ultraviolet protection is required to prolong insecticidal activity effectively.

ISSN:0046-225X    

DOI:10.1093/ee/18.6.1035

出版商:Oxford University Press    

年代:1989

数据来源: OUP