摘要:

A model of the biotic potential of western corn rootworm (WCR),Diabrotica virgifera virgiferaLeConte, adult populations was developed from data presented in the literature. Adult emergence, adult populations, and egg populations were measured in a total of five continuous cornfields in 1982 and 1983. The simulations made with the model suggested that the observed populations of WCR adults and eggs were far below their potential (one-third and one-fifth, respectively). With the use of the biotic-potential model, adult population sizes were simulated by using different mortality (including dispersal) regimes. The results of these simulations suggest that age structure may be important in determining the potential of WCR adult populations. A regime that allowed the earlier emerging adults to remain in the field for a longer period fit the observed adult and egg population data better.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.446

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Fall armyworm (FAW),Spodoptera frugiperda(J. E. Smith), were sampled from cornfields at the St. Gabriel Experiment Station in south-central Louisiana from 1981 to 1983. Data from single-plant samples and five-plant samples for small, medium, and large larvae and total population were fitted to the Poisson, negative binomial, and Neyman type-A distributions, as well as the Taylor power function. None of the three distributions fit FAW populations consistently. The power function provided significant regressions for all eight larval categories and was used to calculate number of samples required for different larval densities for a given confidence level.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.453

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Larvae of gypsy moth,Lymantria dispar(L.), were fed gypsy moth nuclear polyhedrosis virus on selected host plants to study influence of host plants on larval mortality. Larvae consuming the virus on red oak,Quercus rubraL., or red maple,Acer rubrumL., showed significantly lower mean mortality due to the virus than did larvae fed virus on quaking aspen,Populus tremuloidesMichx., or pitch pine,Pinus rigidaMill. Mean viral mortalities for larvae fed red oak, red maple, pitch pine, and quaking aspen were 32.0, 35.4, 44.4, and 49.7%, respectively.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.459

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Major electroantennograph (EAG) activity was associated with five components that were eluted during gas chromatographic fractionation of a sex pheromone extract fromEucosma womonanaKearfott. These components were identified by combined gas chromatograph/mass spectrometry as dodecyl acetate, (Z)-5-dodecenyl acetate, (Z)-7-dodecenyl acetate, (Z,Z)-7,9-dodecadienyl acetate, and (Z,E)-7,9-dodecadienyl acetate. In experiments in the field,E. womonanamales were captured in traps baited with a blend of these five acetates and with a mixture of these acetates and their corresponding alcohols. Males ofIsophrictis similiella(Chambers) also were captured by the acetate blend but not by the mixture of acetates and alcohols. Further experimentation established that addition of either (Z)-7-dodecenol or (Z,E)-7,9-dodecadienol to the acetate blend inhibited capture ofI. similiellabut attractedE. womonana. The best attractant forI. similiellawas a blend of (Z)-5-dodecenyl acetate, (Z)-7-dodecenyl acetate, and dodecyl acetate. Traps placed at a height of 0.3 m caught 6.1-fold moreI. similiellaand 3.0-fold moreE. womonanathan traps at the crop canopy, 1.5 m above ground.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.463

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Horn flies,Haematobia irritans(L.), significantly alter their distribution on cattle treated with pyrethroid-impregnated ear tags in comparison with untreated cattle.H. irritansprefers the largely untreated ventral and posterior regions of tagged cattle. The behavioral resistance to fenvalerate is largely a stimulus-dependent phenomenon, as indicated by the large differences in distribution patterns of a resistant horn fly population on tagged and tag-free cattle in adjacent pastures. Resistant horn flies showed a significantly greater preference for the bellies of tag-free cattle than did susceptible flies. Intensive selection by pyrethroids may also result in a horn fly population that has some degree of stimulus-independent behavioral resistance (i.e., chronic occupation of untreated areas even in the absence of a toxicant).

ISSN:0046-225X    

DOI:10.1093/ee/16.2.467

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Effects of dietary conditioning on feeding behavior on cotton ofHeliothis zea(Boddie) third and fifth instars were examined in a greenhouse study. Larvae were conditioned from hatching to third or fifth instars on field-grown cotton flower buds or an artificial wheat-germ diet. Larvae reared on flower buds fed more, rested less, and locomoted less than larvae reared on the artificial diet. Bud-fed larvae generally preferred feeding on flower buds, whereas larvae reared on the artificial diet preferred feeding on blooms. These data show that feeding responses of later instars on a single cotton cultivar are dependent on dietary conditioning, and that dietary conditioning can affect results of studies involving bollworm feeding behavior.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.471

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

A method of labeling corn plants with the trace element rubidium (Rb) was developed for monitoring wireworm feeding on germinating corn seed and seedlings. The method involved treatment of corn seed with an adhesive solution containing Rb. In a greenhouse experiment, only small amounts of Rb were extracted from soil adjacent to treated plants. In field evaluations, corn was labeled at time of planting and remained labeled for ≤32 d after planting. Rb was transferred to larvae of four species, and concentrations in all wireworms found while feeding on labeled plants exceeded 101 ppm Rb. One-sided 99% tolerance limits calculated from Rb concentrations in wireworms from untreated plots were used as cutoff levels for separating labeled and unlabeled larvae. Percentages of three wireworm populations that became labeled were similar in plots that received seed treatments containing 15, 25, and 35% Rb and in samples obtained between 2 and 32 d after planting. Portions of two populations were obtained from soil adjacent to labeled plants and contained Rb levels similar to naturally occurring concentrations. Seed treatment with Rb provides a sensitive tool for estimating percentages of wireworm populations that feed on corn during its early stages, and also may permit measurements of differences in damage potentials between species and dispersal of larvae after feeding.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.475

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

This study was designed to characterize the patch-utilization strategies of two sympatric species of parasitoids. The hypothesis is presented that sympatric species that use the same range of hosts may exhibit divergent patch-utilization strategies, possibly allowing for coexistence. The species studied wereMuscidifurax raptorGirault&Saunders andM. zaraptorKogan&Legner, pupa parasites of synanthropic fly species in the southwestern United States. Laboratory behavior experiments demonstrated that these species have alternative strategies of patch utilization.M. raptorhas a short handling time and exhibits the apparent strategy of parasitizing as many hosts as possible per patch.M. zaraptorhas a longer handling time and generally enters a patch where it parasitizes a small number of hosts, before leaving quickly to search for other patches. Both strategies are accentuated at high parasitoid densities.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.481

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

We describe effects of constant temperature, beetle density, and time of oviposition on aspects of development, mortality, sex ratio, and size ofIps calligraphus(Germar). Emphasis is placed on individual life stages. Relationships of median development times to constant temperatures were similar for eggs, larvae, and pupae in the 12.5–37.5°C range. These relationships appeared as backward J-shaped curves. Reciprocal development times versus temperatures for these life stages were described by the six-parameter rate function of Sharpe&DeMichele (1977, J. Theor. Biol. 64: 649–670). Development times and foraging distances of larvae increased with each instar. The third instar required 61% of total larval time and excavated 73% of the total larval gallery. Optimum development temperature of teneral adults was not identified, indicating greater tolerance to high temperatures of this stage compared with the others. The four-parameter Sharpe&DeMichele (1977) model (without high-temperature inhibition) described teneral adult rate as a function of temperature. Timing of oviposition influenced development time of larvae (increased development time with late oviposition) and teneral adults (decreased), but not development times of eggs or pupae. Reversed patterns of longer development times for larvae and shorter times for teneral adults canceled any effects of sequential oviposition on length of life cycle. Distributions of development times were generally skewed toward the longer times, and variation around mean time tended to increase with successive life stage. A single, temperature-independent distribution of normalized development times is presented for each life stage and is described by a three-parameter cumulative Weibull function. Stage-specific mortality (resulting from unknown causes) formed partial or full U-shaped patterns when plotted against temperature. Density-dependent mortality resulting from cannibalism is discussed, with a Weibull function describing influence of egg density on probability of being cannibalized. Timing of oviposition influenced percentage of mortality of all life stages, primarily due to increased cannibalism of later-developing brood. An overall sex ratio of 1:1 was observed, but proportion of males to totalI. calligraphusincreased from 0.374 in the first quarter of the emergence period to 0.569 in the fourth quarter. Beetles reared at 15–25°C were somewhat larger than those reared at 30–35°C. Generally, males were slightly larger than females when size was examined relative to time of emergence. An inverse relationship of beetle size to time of emergence was observed for each sex.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.484

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Constant temperatures from 12.5 to 37.5°C influenced duration of the within-tree life cycle (egg to adult emergence) ofIps calligraphus(Germar). The relationship of median development time and constant temperature formed a backwards J-shaped curve. On the average, developingI. calligraphusspent as little as 18 d in the host at 35°C and as much as 224 d in the host at 12.5°C. Frequency distributions of development times changed with temperature and were nearly uniform at 15°C, more symmetric at 20–3O°C, and somewhat skewed to the right at 32 and 35°C. The model of Sharpe&DeMichele (1977, J. Theor. Biol. 64: 649–670) described development rates (reciprocal of median times) as a function of temperature (R2= 0.999), and a cumulative Weibull function (Wagner et al. [1984b, Ann. Entomol. Soc. Am. 77: 475–487]) described a single, temperature-independent distribution of normalized development times (R2= 0.997). Combined, these functions predicted cumulative proportions of cohort emergence through time. Models were validated using a multiple-cohort simulation procedure (Wagner et al. [1985b, Ann. Entomol. Soc. Am. 78: 691–704]) as well as data onI. calligraphusemergence from three trees in each of three field plots. The validation suggested the model's suitability in a larger model of population dynamics.

ISSN:0046-225X    

DOI:10.1093/ee/16.2.497

出版商:Oxford University Press    

年代:1987

数据来源: OUP