摘要:

The phenology ofEryniaepizootic development among larval alfalfa weevil,Hypera postica(Gyllenhal), populations in central Kentucky during 1979 through 1982 is described. Critical biological and physical factors governing initiation, progression, and termination of the epizootic under field conditions are identified. The first incidence ofEryniadisease inH. posticain central Kentucky occurred between 200 and 290 celsius day-degrees accumulated from 1 January, using a base temperature of 9°C. Day-degrees were used to initiate annual field sampling but did not fully explain differences in overall epizootic phenology. Although the general sigmoid shape ofEryniaepizootic mortality curves were very similar in 1979 through 1982, certain microclimatic factors appeared to dictate the magnitude and duration of the epizootics after first incidence of disease was observed. It is proposed that accumulated moisture above a base humidity threshold can serve as a key factor for explaining epzootic behavior as related to favorable and unfavorable conditions for conidial development and discharge. Natural termination ofEryniaepizootics occurred when host densities fell below a critical threshold density value of 1.7 larvae per stem.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1350

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

A cause and effect relationship was demonstrated between cotton leafworm,Alabama argillacea(Hübner), larval crowding, and increased parasitism by the pupal parasiteBrachymeria ovata(Say). In overcrowded conditions the larvae exhibited a conspecific-destructive reaction by resorting to eating the leaf covering from the pupae of their own species, thus destroying needed protection from natural enemies. The minimum larval density required before larvae consumed pupal leaf covers and exposed the pupae was l8.4/m of row, with a larval density of 142.l/m of row resulting in almost complete defoliation and consumption of most pupal covers. Parasitism of covered pupae byB. ovatawas 1.0 ± 0.6 to 4.9 ± 1.7%, whereas 30.3 ± 9.7 to 46.6 ± 6.2% of the exposed pupae produced under crowded conditions were parasitized. Intraspecific competition between the cotton leafworm larvae and pupae is unequal because the larvae have a marked effect on pupal survival, but there is no detectable, reciprocal effect on the larvae. In most cases of intraspecific competition, the relatively successful individuals are those that begin and complete development first. However, in the case of the cotton leafwonn, the opposite may be true.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1356

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

The numerical behavior of populations of the western spruce budworm,Choristoneura occidentalisFreeman, was analyzed by using life table data from north-central Washington and central Idaho. The survival rate of instars IV through VI was lowest at budworm densities below ca. 10 4th instars per m2of foliage. This rate was fairly stable (0.2 to 0.6) across higher densities (10 to 40 per m2of foliage). The survival rate of pupae from predation increased from ca. 0.2 among the least dense populations to ca. 0.8 among the most dense ones. Survival among the remaining pupae was systematically lower among the populations in Washington than among those in Idaho. The survival rate of eggs and instars I to III was not a function of budworm egg density, place, year, or host species. When density was low, observed egg density was sometimes greater than the ability of resident females to produce eggs. Conversely, at high densities observed egg density was always lower than the egg-laying potential of resident, emerging females. Adult female behavior, together with a generally positive relation between density and subsequent survival during the large larval and pupal stages, may profoundly influence the population dynamics of this pest.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1360

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

By use of a two-choice laboratory bioassay, olfactory response to beetle and frass volatiles was assessed inOryzaephilus surinamensis(L.) andO. mercator(Fauvel) of known age and mixed sex from cultures held at various adult population densities. Four- to 6-week-postemergentO. surinamensisfrom dense laboratory cultures (~40,000 beetles per kg of medium) did not respond to, or were repelled by, Porapak Q-captured volatiles from beetles, frass, rolled oats, and brewer's yeast. When culture density was lowered to 1,000 beetles per kg or when beetles>2 months posteclosion were tested, positive olfactory response to test volatiles progressively developed. Recently eclosedO. surinamensisfrom low-density cultures exhibited a period of negative attraction or no significant response to test volatiles, followed by a gradual increase in positive response. In contrast, forO. mercatormaintained in moderately crowded cultures (10,000 beetles per kg), positive olfactory response to beetle and frass volatiles developed during the week after adult eclosion.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1367

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Oviposition rates of western bean cutworm,Loxagrolis albicosta(Smith) (Lepidoptera: Noctuidae), were determined throughout the ovipositional period for 3 years in three to five com hybrids with different day-degree requirements, each planted on two to three dates. Number of eggs laid was found to be related to both factors. Overall, plots with the earliest mean growth stage tended to receive the greatest number of eggs at all sampling dates. In 1 year, oviposition began while growth stages were earlier than in the other 2 years. Egg distribution for that year showed a tendency for plants that were just beginning to tassel to receive more eggs than earlier or later growth stages. The relationships between adult light trap catches and total oviposition in the experimental area appeared similar in the 3 years regarding magnitude and timing of peak numbeŕs and duration of activity.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1375

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

More than 50% of crucifer-feeding flea beetle (Coleoptera: Chrysomelidae) adults trapped on 1-m column traps in a rutabaga field were taken at less than 20 cm from ground level. The mean length of jump ofPhyllotreta cruciferae(Goeze) is 25 cm. Cylindrical traps painted red and coated with Tangletrap were used with statistics of directional data to measure immigration and emigration of adults. There were four immigration episodes and seven emigration episodes during the season.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1380

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Two mycangial fungi,Ceratocystis nigracarpaDavidson and an unidentified basidiomycete, were isolated from the walls of pupal chambers made byDendroctollus brevicomisLeConte, along with another fungus,Ceratocystis minorHedge, which is closely associated with the beetle but not found in thc mycangium. Beetles eclosing to the adult stage under axenic conditions had empty mycangia, whereas those eclosing within the pupal chambers acquired spores of both mycangial fungi. Beetles emerging from standing trees had only spores in their mycangia. However, beetles responding to pheromone-baited trees had mycangia filled with spores and mycalia, as did ovipositing females removed from under the bark of newly colonized ponderosa pine. Thus, there is an 8- to 10-day delay between the time beetles emerge and the time the fungi grow and completely fill the mycangium. Beetles apparently do not colonize trees during this time, which suggests that there is a lag between emergence of new adult females and responsiveness to pheromone.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1384

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

In field tests with the two component sex pheromone ofAmorbia cuneana, (E.Z)-10,12- and (E,E)-10,12-tetradecadien-1-ol acetates, optimum trap catches were obtained with an isomer content of 29 to 82% EZ (as a percentage of EE + EZ), and dosages of 0.06 to 1.7 mg per rubber septum (using a bait of 62% EZ). There were slightly larger catches for the bait with 53% EZ than for others in the 29 to 82% range. Individual native femaleA. cuneanamoths contained an average of 54.8 ± 10.2% EZ (range = 33.7–69.6% EZ). Traps baited with synthetic pheromone caught as many males as traps baited with females. Catches were higher when rubber septa were used to dispense the pheromone than when polyethylene caps were used. A synthetic contaminant, (E)-/(Z)-10-dodecen-1-ol acetate, was found to be moderately inhibitory. Rubber septa baited with synthetic pheromone and aged in the field for 90 days were as effective as fresh baits. During the entire aging period of 120 days, the EZ isomer content changed from 62 to 33%.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1387

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Life tables were constructed for six generations ofRhyacionia frustrana(Comstock) and for one generation ofRhyacionia rigidana(Fernald) in a 2- to 3-year-old loblolly pine plantation. Overlapping stage-density trend curves were estimated for each generation by a schedule of two-stage cluster samples. Population models were applied to these curves to estimate stage recruitments for the life tables. Important mortality occurred during egg and pupal stages. Egg mortality was high, and perhaps density dependent.Triehogrammasp. caused much egg mortality in generations 2 and 3, but an unknown factor caused most generation 1 egg mortality. Fifth-instar larvae were heavily parasitized byLixophaga mediocrisAldrich, but this mortality was constant and was not a key factor. Some pupal mortality was caused by parasites. However, sources of most pupal mortalily were not identified. The pattern of survivorship forR. rigidanawas similar except for high 1st-instar mortality, apparently due to resin from feeding wounds on pine Shoots. Sex ratios and fecundities were also examined.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1391

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Bacillus thuringiensisvar.kurstakiBerliner andHeliothisnuclear polyhedrosis virus (NPV) formulations Dipel and Elcar, respectively, were tested in spray mixtures with several chemical pesticides: benomyl, chlorothalonil, fentin hydroxide, and thiabendazole (fungicides); methoprene and diflubenzuron (insect growth regulators); cyhexatin (acaricide); and chlordimeform (insecticide-acaricide) on cotton foliage. Foliage from treated plants was fed to first- and third-stageHeliothis virescens(F.) larvae. First-stage larval mortality response from microbial agent-chemical pesticide mixtures varied from synergistic to antagonistic.B. thuringiensiswith either acaricide, chlordimeform or cyhexatin, andHeliothisNPV-chlordimeform produced the highest mortality above the expected levels. Mixtures of either microbial agent with chlorothalonil and diflubenzuron-B.thuringiensisresulted in significantly less mortality than the expected levels. No synergism was observed when third-stage larvae were exposed to the mixtures.B. thuringiensis-fentinhydroxide or diflubenzuron andHeliothisNPV-fentin hydroxide mixtures were antagonistic.B. thuringiensis-chlorothalonil was also antagonistic when mortality was recorded at pupation.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1403

出版商:Oxford University Press    

年代:1983

数据来源: OUP