摘要:

Two flight periods ofChoristoneura rosaceana(Harris) were detected in a mixed forest near Quebec City using pheromone traps baited with the synthetic lure, Biolure, or newly emerged virgin females. During both flights, Biolure was considerably less attractive thanC. rosaceanavirgin females. Additional field tests using different compositions, ratios, and concentrations ofC. rosaceanasex pheromone showed that blends containing three components (Z11-14: Ac, E11-14: Ac, Z11-14:0H) were more attractive than blends containing acetates only. Furthermore, the attractiveness of lures containing Z11-14: OH increased with concentration irrespective of the different ratios of Z11-14: Ac and the flight period, whereas no such effect was observed with lures containing acetates only. Moreover, during the summer flight males responded preferentially to the three component blends with a high rather than low ratio of Z11-14: Ac to Ell-14: Ac, although no differences were detected during the fall. This trend was observed irrespective of the concentration and the level of Z11-14: OH. The importance of using the appropriate pheromone blend to monitor each flight period ofC. rosaceanawill be discussed in relation to the seasonal biology of the parasitoid,Meteorus trachynotusVier, an important natural enemy of the spruce budworm that requiresC. rosaceanaas an overwintering host.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1007

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Sampling studies were conducted to assess intra- and interplant dispersion of pepper weevil,Anthonomus eugeniiCano, adults and to compare adult sampling methods. More weevils were observed on fruiting buds than on other plant structures, and adult numbers varied diurnally on the exposed portions of the plant. The number of pepper weevil adults on exposed terminal buds was significantly higher in the morning than the afternoon. Interplant dispersion estimates using terminal bud inspection suggested that pepper weevil adults are clumped (Taylor's Power Law:b= 1.2, sample unit = five contiguous plants, two terminal buds per plant) in commercial bell-pepper fields. A concentration of pepper weevil in the field margins was observed at two farm sites. Taylor's Power Law coefficients did not vary significantly over time or with changes in population density, but the slopebwas sensitive to pepper variety and sample position on the plant. Variance-to-mean ratios and Morisita's index were affected by quadrat size. A comparison of terminal bud inspection, whole plant inspection, and an absolute sample for pepper weevil adult counts indicated that terminal bud inspection had a greater relative net precision than whole plant inspection.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1013

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

This study addressed the potential effects on Hawaii's unique fauna of protein bait sprays used in fruit fly eradication programs. We sampled the ground litter-inhabiting invertebrates attracted to protein hydrolysate-baited pitfall traps at six localities on the island of Kauai. Twenty-two taxa and possibly 30 species were found in significantly higher numbers in treatment than in control traps. A diverse fauna, including species of land snails (Gastropoda), isopods (Isopoda), millipedes (Diplopoda) and insects (nine families), was attracted to the bait. Flies in the family Drosophilidae may be particularly susceptible to bait sprays, with at least eight species demonstrating attraction. Traps in high-elevation native forest attracted the highest number of species (20) and the most native species (11). The number of native species attracted to the bait decreased with elevation and the proportion of native vegetation, so that no native species were recovered from the two low-elevation agricultural areas. The potential effect of using protein hydrolysate bait sprays for alien fruit fly control in Hawaii is discussed.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1022

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Field sampling of the Russian wheat aphid,Diuraphis noxia(Mordvilko), infesting spring wheat, spring barley, and winter wheat in the northwestern United States from 1988 to 1991 generated a data set of 117 mean aphid density(m)and variance(S2)estimates, based on individual tillers, with an average sampling error level of 0.172. This provided a data set desired for use in spatial analysis and the development of sampling plans. Three regression models-ln(s2) = ln(a) +bln(m) (Taylor's power law), m* = α +βm(Iwao's model), andk=c+ dm [k=m2/(s2−m) (a parameter for the negative binomial distribution)—were fit to the data pooled by crop type or growing season. Taylor's power law generally fit the data better than Iwao's model. Taylor'sband Iwao'sβwere significantly ≤1 for all cases (single crop, season, or pooled together), indicating thatD. noxiapopulations were aggregated. The slope d for the summer populations on winter wheat was indistinguishable from 0, indicating the existence of a commonk(estimated as 0.003). However, a commonkwas not detected for the summer populations on spring wheat and barley and the fall populations on winter wheat because theirdvalues were Significantly ≤0, indicating the dependence ofkonm. Based on comparisons of intercepts and slopes from the three models, the counts of the summer populations on all three grains could be pooled effectively to generate a more representative data set covering a wide range of variation. However, the fall populations on winter wheat should be treated separately because their spatial pattern apparently is distinct from those of the summer populations. Finally, temporal changes in spatial pattern (represented by the estimates of1/k) on spring and winter grains are discussed with respect to crop stages and aphid densities.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1029

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

This study was designed to evaluate biases associated with four methods of estimating stage-specific parasitism and one method of estimating time-specific parasitism for two parasitoids attacking gypsy moth,Lymantria dispar(L.), larvae. Estimates for all five methods were calculated using both observed death rates and marginal attack rates. Calculating percentage parasitism by pooling all hosts collected during the season resulted in an underestimation of stage-specific parasitism by bothCotesia melanoscela(Ratzeburg) andParasetigena silvestris(Robineau-Desvoidy). Percentage parasitism byC. melanoscelapeaked after completion of recruitment of hosts and parasitoids and before substantial losses (death or emergence) of either hosts or parasitoids. Consequently, peak sample percentage parasitism was an unbiased estimate of stage-specific parasitism byC. melanoscela. Oviposition and emergence ofP. silvestrisoverlapped considerably with each other and also with losses of hosts not parasitized byP. silvestris. As a result, the peak value of percentage parasitism was not appropriate for use with this species. The release of laboratory-reared larvae (trap-hosts) to directly measure the number of parasitoids recruited into the susceptible stage of the host did not provide accurate estimates of percentage parasitism by either species, possibly because of different sizes and behaviors of trap-host larvae. The graphical method of estimating numbers entering a stage used by Southwood&Jepson in 1962 is unbiased only if minimal mortality occurs during sampling. This was true forC. melanoscela, but not forP. silvestris. Mortality of parasitized hosts can also affect estimates of time-specific parasitism of hosts collected in the field. Because mortality of gypsy moths parasitized byP. silvestriswas high, this method is not recommended forP. silvestris, and an alternative technique is suggested.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1035

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Poor survival and reproduction of the aphidRhopalosiphum padi(L.) was observed on tall fescue plants infected with the endophytic fungusAcremonium coenophialumMorgan-Jones&Gams. Reproduction was always much higher on uninfected plants, but on older infected plants, someR. padisurvived long enough to molt and reproduce. In choice studies,R. padiand the greenbug,Schizaphis graminum(Rondani), preferred uninfected fescue plants. Greenbugs quickly destroyed their uninfected hosts and died. ThoseS. graminumthat moved to infected plants also died. High numbers ofR. padion fescue plants could be a reliable indicator for the absence of endophyte-associated alkaloids that cause resistance to a number of other insect herbivores.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1046

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Field studies were conducted in western Montana during 1985 and 1986 to determine the voltinism, sex ratio, and the phenological synchrony ofUrophora affinisFrauenfeld andU. quadrifasciata(Meigen), two flies introduced for biological control of spotted knapweed. Varying percentages of adults of both fly species emerged in late July through September for a second generation. Mean percentage second-generation emergence ofU. affiniswas 7.1 compared with 35.2 forU. quadrifasciata. Percentage of second-generation emergence for both fly species was highest in the earliest maturing seed heads and decreased gradually in later-maturing seed heads. Ninety percent of second-generation emergence occurred within 2–3 wk of seed-head maturation. A small number of both fly species emerged in September for what may be a third generation. First-generation emergence ofU. affinisandU. quadrifasciatapeaked on 25 June and 2 July, respectively, while peak second-generation emergence of both fly species occurred on 19 August. Peak first-generation emergence of females of both fly species from previous year seed heads of spotted knapweed occurred when the majority of current-year flower heads were 2–4 mm in diameter, while second-generation emergence occurred immediately after the infested seed heads had opened for seed dispersal. Males of both fly species generally emerged earlier than females in both emergence periods, but the male-to-female ratio in the first half of the emergence periods was higher forU. affinisthan forU. quadrifasciata. The distinct differences in voltinism and associated survival strategies serve as key factors in the niche separation of the two species. AlthoughU. affiniswill likely become the dominant species at sites where the two flies coexist, the two flies' niche separation will probably ensure the continued presence ofU. quadrifasciatain North America.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1052

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The effects of drought stress and stem tunneling by European corn borer,Ostrinia nubilalis(Hübner), on water relations of field corn,Zea maysL., were evaluated in 1987 and 1988. Using a pressure chamber, leaf and stem water potentials averaged 3.8 and 3.5 bars, respectively, higher in plants from well-watered soils compared with droughtstressed plants. Larval tunneling had no effect on the leaf or stem water potential. A vacuum infiltration technique was developed to examine the effects of these factors on stem hydraulic conductance and provided hydraulic conductance measurements comparable with that predicted with the Hagen-Poiseuille equation.O. nubilalistunneling reduced the internode hydraulic conductance by up to 63.5% compared with undamaged stems, and slight reductions were also seen with conductance through intact stems (internode with attached node). The node appeared to mitigate the effects of tunneling on hydraulic conductance in intact stem sections. Soil moisture status had no effects on hydraulic conductance as measured with the vacuum infiltration technique.O. nubilalistunneling, from a Single larva, rendered an average of 36.6% of the medullary xylem vessels nonfunctional and also slightly reduced the functioning of the peripheral xylem vessels. Finally,O. nubilalistunnel dimensions averaged 783.1 mm3in volume, and 46.7 mm in length, and 9.2% of the stem area was tunneled. Tunnel dimensions were generally similar in stem sections from plants from fully irrigated and drought-stressed soils. Tunnel measurements related to cavity volume and cross-sectional area destroyed were more closely correlated with hydraulic conductance than were tunnel length or shape. The majority of damage to the plants' vascular system, as reflected by hydraulic conductance, stained vessels, and cavity dimensions, occurred during the first 6 d of tunneling.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1060

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Biotype E green bugs from populations maintained either on Corn,Zea maysL., or grain sorghum,Sorghum bicolor(L.) Moench., were studied to determine their ability to use Corn as a host in the field. Two Corn germplasm accessions (‘Antigua’ and OH-45), two commercial Corn hybrids (AGRIPRO-AP670andASGROW/OSGOLD-2570), one susceptible grain sorghum (NC+630x), and two resistant sorghums (PI264453 and PI266965) were used. Daily mortality and fecundity schedules were measured, and demographic statistics were calculated. In general, longevity was greater for Corn-reared than for sorghum-reared greenbugs. All life history measures indicated that green bugs did as well on ‘Antigua’ Corn as on sorghum. However, of 64 greenbugs tested on OH-45 and ASGROW/OS GOLD-2570, only 1 and 6, respectively, survived to adulthood. Development time was significantly longer on OH-45, AGRIPRO-AP670, and ASGROW/OS GOLD-2570 for the first, second, and third instars, but not the fourth. This supports early greenhouse studies suggesting that green bugs can physiologically adapt to a new host. These results indicate that greenbugs can develop and reproduce to some extent on commercial Corn hybrids in the field, but not as well as suggested by greenhouse studies.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1072

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Procerum root disease caused byLeptographium procerum(Kendrick) Wingfield is the most serious disease problem facing Virginia Christmas tree growers producing eastern white pine,Pinus strobusL. Studies have shown an association between procerum root disease-affected trees and insect infestations, andL. procerumhas been recovered from field-collected insects. To determine the species and spatial distribution within Christmas tree plantations, potential insect vectors were collected weekly, April-September 1988–1991, from plots containing baited pitfall traps. Plots were located in plantations with procerum root disease, plantations without procerum root disease, in forested areas outside both types of plantations, and in an urban setting. Trees within the plots were inspected for development of procerum root disease. Insects recovered included two weevil species,Hylobius pales(Herbst) andPissodes nemorensisGermar, and bark beetles from the generaIpsDe Geer,PityophthorusEichoff,PityogenesBedel,OrthotomicusFerrari, andXyleborusEichoff. In plantations with procerum root disease, there were Significantly more (P ≤ 0.05) H.palesthanP. nemorensis, and Significantly more H.paleswere contaminated withL. procerum.In plantations where procerum root disease was absent, there was no significant difference between the numbers of either weevil species or proportions contaminated with the fungus. Within the plots with procerum root disease, 27% of the trees developed symptoms of the disease during 3 yr of observation, but no trees developed disease symptoms in the asymptomatic plots.

ISSN:0046-225X    

DOI:10.1093/ee/21.5.1077

出版商:Oxford University Press    

年代:1992

数据来源: OUP