摘要:

A nearest-neighbor discriminant analysis based on the frequencies of occurrence of six random amplified polymorphic DNA markers was used to identify individuals from an insecticide-resistant laboratory biotype (SEL) of the walnut aphid parasiteTrioxys pallidusafter release into three California walnut orchards. Releases of SEL individuals were made in a Hanford, CA, orchard in 1988 and in a Gridley, CA, orchard in 1989. Nearest-neighbor analysis of postrelease collections from both the Hanford and Gridley orchards showed a continuing influence of the SEL biotype up to 3 yr after the release. SEL individuals also were released in a Hed Bluff, CA, walnut orchard in 1991. At this orchard, SEL males were recovered from the release area throughout the season of release, but a June 1992 sample indicated that no SEL individuals remained in the orchard. Comparison of observed data at Hanford and Gridley to simulated hybrid data provided evidence that there was interbreeding between the SEL and the native field biotypes. Bioassays indicated that the level of azinphosmethyl resistance in these two orchards was intermediate between the level in the orchards before release and the level in the pure SEL biotype. Therefore, the release of pesticide-resistantT. pallidusin two California walnut orchards significantly increased the level of resistance, but did not completely displace the native populations, despite multiple treatments of postrelease populations with azinphosmethyl.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.487

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Distribution of five species of tropical insect herbivores was recorded in relation to gradients of modular length on their host plants. Patterns in plant architecture and herbivore responses were compared with a well-studied temperate herbivore,Euura lasiolepisSmith (Hymenoptera: Tenthredinidae). The five tropical species were each from a different family, and host plants belonged to different families and vegetation types. Using modular gradients of shoot or leaf length we showed that plant architecture was comparable directly and was similar even when trees, shrubs, and grasses were compared. Also, the membracid, cicadellids, psyllid, and cecidomyiid in the tropics showed patterns of attack on modular gradients consistent with the patterns derived from high ovipositional preference linkage with larval performance, known to exist in the temperate species. Strong positive relationships between module length and percentage of modules attacked in each length class were observed, with variance accounted for ranging from 68 to 96&. One pest species on forage grasses in the vicinity of Brasilia,Deois flavopictaStal (Homoptera: Cercopidae), showed a weak response to the shoot-length gradient of its host grass (r2= 0.41) and an insignificant response per unit length of shoot, suggesting a generalized capacity to use wide variation in module size. A method was developed for direct comparison of species employing a comparison between a hypothetical ideal response to modular gradients and the actual response. The actual slope of the attack versus module length regression, expressed as a percentage of the hypothetical slope, provided estimates of herbivore responses to modular plant structure consistent with hypotheses on plant vigor and phylogenetic constraints.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.497

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Spatial distribution (quantified by Taylor's power law) and population densities of three scale insect species (Homoptera: Coccoidea) were investigated. The olive scale,Parlatoria oleae(Colvee), was studied on young and old twigs, and on the spurs of apple trees. The Israeli pine bast scale,Matsucoccus josephiBodenheimer et Harpaz, was studied on the stem, branches, and crown ofPinus halepensisMiller. The effect of fruit phenology on the spatial distribution of the citrus mealybug,Planococcus citri(Risso), was studied on grapefruit trees. The highest density of the olive scale was registered in the spurs, whereas the Israeli pine bast scale was more abundant on the stem. The citrus mealybug was more abundant during October. There was no effect of the host section or phenology on the within-species distribution of the three scales, supporting previous claims that the species level of aggregation is a species constant. The species index of aggregation for the three scale insects was 1.3 for the olive scale, 1.9 for the bast scale, and 1.6 for the citrus mealybug. It is suggested that the observed spatial patterns are the result of the intrinsic behavior of the scales (e.g., thigmotaxis and negative phototaxis during crawlers dispersal), the morphological characteristics of the host-plant tissue, and the differential activity of natural enemies. The relatively low level of aggregation of the olive scale is probably related to the activity of an efficient natural enemy, a factor which is negligible in the other two scale species.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.506

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

ThirteenLycopersiconaccessions were compared for landing of the western flower thrips,Frankliniella occidentalis(Pergande), on leaves and flowers and resistance to tomato spotted wilt tospovirus (TSWV) in field experiments on the Hawaiian island of Maui. Occurrence of the onion thrips,Thrips tabaciLindeman, and the greenhouse whitefly,Trialeurodes vaporariorum(Westwood), on leaves was also recorded. Adult western flower thrips occurred on all Lycopersicon accessions, and no significant difference was found among accessions in western flower thrips landing per leaf. Significant differences were found among accessions with regard to number of western flower thrips occurring per flower and incidence of TSWV. Landing of onion thrips and greenhouse whitefly on leaves varied significantly among accessions.Lycopersicon esculentumMill. ‘Anahu’ was the only accession infected with TSWV at the foliar stage.L. esculentum‘Pearl Harbor’, ‘L. paroiflorum(Jusl.) Mill., andL. hirsutumHumb. and Bonpl. were infected after flowering, and TSWV infection was not observed inL. peruvianum(L.) Mill.,L. hirsutumf.glabratumC. H. Mull., L.chmielewskiiRick et al.,L. pennellii, L. pimpinellifolilum(Jusl.), andL. chilenseDun. even after 7 mo in the field, suggesting field resistance in these accessions. AmongL. esculentumcultivars, ‘Rey de los Tempranos’ was the only accession that did not become infected with TSWV. Because thrips landing did not correlate with TSWV infection in our experiment, we suggest that TSWV susceptibility and thrips feeding after landing are likely more important in influencing virus incidence under field conditions than landing behavior or direct resistance to insect colonization.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.513

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A control decision rule for European chafer,Rhizotrogus (Amphimallon) majalis(Razoumowsky), larvae infesting turfgrass was developed using data from 317 residential sites. Larvae were often abundant enough to cause damage to turf in portions (patches) of properties when average density over an entire site was much less than a damage threshold of 5–10 grubs per 950 cm2. To account for this, an empirical relationship between the size of the largest patch of European chafer larvae at a site and site-wide density was used in the development of the decision rule. Properties with a patch of grubs in excess of ≍30 m2were deemed to require insecticide treatment. Site characteristics (lawn age, shade, and percentage of Kentucky bluegrass) were related to site-wide density and this relationship was used to formulate a risk assessment system. This system is used to determine whether a site should be sampled or not. Properties that are not sampled are not to be treated. Other treatment decisions are based on the outcome of sampling. The relationship between site-wide density and patch size did not allow clear identification of a density that could be used as a threshold in a sampling program. Therefore, several sampling plans were constructed that classified density according to different threshold values. Operating characteristic functions were used in combination with the aforementioned relationship between density and patch size to calculate two types of errors for each sampling plan: the probability of not treating when treatment was necessary and the probability of treating when treatment was not required. Based on these error functions, a threshold of 0.25 grubs per ll-cm diameter turf plug was advocated. Use of the proposed control decision rule should result in few treatment errors but could lead to considerable reductions in pesticide use.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.521

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Outbreaks of the gypsy moth,Lymantria dispar(L.), typically occur over large areas but are difficult to predict. Most gypsy moth management programs base suppression decisions on models that predict defoliation from preseason counts of egg masses in a given stand. In this study we developed a statistical model that used spatially stratified egg mass samples to predict gypsy moth defoliation on a regional scale, rather than on a stand level. The model was developed from historical defoliation sketch-map data and counts of gypsy moth egg masses under burlap bands at irregularly distributed plots in Massachusetts. These counts were used to generate interpolated surfaces of egg mass counts in grid cells (2 by 2 km) throughout the state. Maximum-likelihood procedures were used to parameterize a logistic regression model that predicted the probability of defoliation in each grid cell as a function of interpolated egg mass counts, the presence of defoliation in the previous year, and the 30-yr frequency of defoliation. Predicted probability surfaces tended to align mostly with the distribution of actual defoliation in each year. The model appeared to perform better than a previous model that was based on three-dimensional kriging of defoliation.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.529

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Weekly sampling ofDiuraphis noxia(Kurdjumov) infesting wheat and barley at four sites in northern Idaho was conducted during the growing seasons from 1989 to 1992. Infestations were higher in the spring-planted than in the fall-planted cereals. Populations ofD. noxiabegan increasing during inforescence emergence, Zadoks growth stage (ZGS) 50, and reached peak numbers during dough development and caryopsis ripening, ZGS 80–90.D. noxiainfestations were highest during 1990 and lowest during 1992. Three survey methods were compared. These included collection of 100 seedlings or tillers per sample for Berlesc extraction, an in-field examination of 500 tillers per sample, and an area wide suction trap sample. Results of the comparisons revealed higher mean numbers ofD. noxiaper tiller from the Berlese method than from the field count method. Comparison of field results with the suction trap collections revealed a definite temporal relationship, suggesting that suction trap counts reflect emigration following local field build up of cereal aphids infesting grain in northern Idaho rather than long distance immigration. Data collected over time from suction trap catches may be useful in predicting future field infestation rates, but will not eliminate the need for field surveys.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.538

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Species composition ofErythroneuraleafhoppers infesting the 3 major classes of grapes grown in New York was investigated. Eastern grape leafhopper,E. comes(Say), comprised 74–100% of populations collected on the native American (Vitis labruscaBailey) cultivars ‘Concord’, ‘Niagara’, ‘Catawba’ and ‘Delaware’. On interspecific hybrid (Vitis sp.) andVitis viniferaL. cultivars,E. comeswas largely absent, and 97–100% of leafhoppers collected were 2 cryptic species,E. bistrataMcAtee andE. vitifexFitch. On the native American variety ‘Elvira’, aV. labrusca X V ripariaMichaux hybrid, field populations were 24%E. comesand 74% theE. bistrata/vitifexcomplex.E. vitis(Harris),E. tricintaFitch, andE. vulnerataFitch were also present in commercial grapes, but never exceeded 20% of the populations sampled. Populations on wildV. ripariaadjacent to vineyards were comprised of 24%E. comes, 47%E. histrata/vitifex, 19%E. vitis, and 10%E. tricinta. Dissection revealed that proportions ofE. bistrataandE. vitifexin field collections, varied from 97%E. bistratato 61%E. vitifex. Oviposition ofE. comesandE. bistrataonV. vinifera, interspecific hybrid, and native American cultivars was compared in greenhouse choice tests and field no-choice tests. In choice tests,E. comeslaid more eggs on Concord and Elvira than on the interspecific hybrid ‘Seyval blanc’, or theV. viniferacultivar ‘White Riesling’.E. bistratadid not oviposit on Concord when paired with either Elvira, Seyval blanc or White Riesling. When caged to grape leaves in no-choice tests,E. comeslaid the most eggs on native American cultivars and the fewest onV. viniferaand interspecific hybrids;E. bistratalaid the most eggs on hybrid andV. viniferacultivars, and very few eggs on three native American cultivars. These results show thatE. bistrataandE. vitifexare the principal pest species onV. viniferaand many interspecific hybrid cultivars in New York, and thatE. comesis the principal leafhopper pest on native AmericanV. labruscacultivars.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.550

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Population densities of a predatory ground beetle,Pasimachus elongatusLeConte (Coleoptera: Carabidae), were examined at the Central Plains Experimental Range, Colorado. Using distance sampling theory, I analyzed density estimates dating from before an application of the insecticide methamidophos (1988) and three beetle generations afterward (1994) to address the following questions. Have population densities ofP. elongatusrecovered to prespray levels? Are current population densities ofP. elongatusin areas exposed to methamidophos in 1988 equal to those not exposed in 1988? How do population densities ofP. elongatusvary with habitat type in methamidophos exposed and nonexposed areas? This work updates earlier findings thatP. elongatuspopulation densities decreased after methamidophos applications. Lingering differences inP. elongatusdensities were found among areas differing in methamidophos exposure; these differences were also related to habitat type. Higher population densities were found in methamidophos exposed than in control areas; higher densities were also found in shrub dominated than in grass dominated sites, regardless of past methamidophos exposure. Because potential prey species were found to be equally abundant in methamidophos exposed and nonexposed areas despite the greater abundance of the carnivorousPasimachusin treatment areas, theP. elongatusdensity patterns seen are discussed in relation to possible long-term disruption of the arthropod prey community by methamidophos. Other explanations for the observed patterns (including competitive release and physiological resistance) are also discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.559

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The postdiapause developmental rates of the European corn borer,Ostrinia nubilalis(Hübner). were investigated using collections of larvae from several selected sites in North Dakota from 1990 to 1992. Significant differences in days to pupation for postdiapausing larvae were found between different geographic locations, and between bivoltine and univoltine populations of the European corn borer in North Dakota. The differences in the time required for postdiapause development is believed to be the major contributing factor responsible for voltinism of the European corn borer population in Nort Dakota. Larvae from most of the sites had some degree of similarity to the bivoltine population, as measured by the proportion of the larvae pupating at ≤220 DD. Retention of the bivoltine trait allows a mechanism for the expression of a second generation in populations that had been considered univoltine. Retention of the bivoltine trait supports the importance of local adaptations in determining the voltinism of European corn borer populations in the northern Great Plains.

ISSN:1754-5692    

DOI:10.1093/ee/24.3.564

出版商:Oxford University Press    

年代:1995

数据来源: OUP