摘要:

Outbreaks of the gypsy moth,Lymantria dispar(L.), were partially synchronous across the New England states (Massachusetts, Maine, New Hampshire, and Vermont) from 1938 to 1992. To explain this synchrony, we investigated the Moran effect, a hypothesis that local population oscillations, which result from similar density-dependent mechanisms operating at time lags, may be synchronized over wide areas by exposure to common weather patterns. We also investigated the theory of climatic release, which postulates that outbreaks are triggered by climatic factors favorable for population growth. Time series analysis revealed defoliation series in 2 states as 1st-order autoregressive processes and the other 2 as periodic 2nd-order autoregressive processes. Defoliation residuals series computed using the autoregressive models for each state were cross correlated with series of weather variables recorded in the respective states. The weather variables significantly correlated with defoliation residuals in all 4 states were minimum temperature and precipitation in mid-December in the same gypsy moth generation and minimum temperature in mid- to late July of the previous generation. These weather variables also were correlated strongly among the 4 states. The analyses support the predictions of the Moran effect and suggest that common weather may synchronize local populations so as to produce pest outbreaks over wide areas. We did not find convincing evidence to support the theory of climatic release.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.987

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The development and fecundity of the citrus rust mite,Phyllocoptruta oleivora(Ashmead) were studied under constant temperatures ranging from 14 to 31°C. The developmental threshold based on mean generation time was 11.07°C. The highest developmental rate occurred at 29°C. The intrinsic rate of increase, net reproduction, total egg production, and mean generation time were fitted to functions of temperature. The optimal temperature for mite population growth as measured by both r andR0was ≈25°C. The cumulative emergence and egg production wcre fitted to 2-variable logistic distribution functions of temperature and cohort age. The probability density function is also derived and truncated so that it will integrate to 1 over time between 0 and + ∞. In our case, ignoring the truncation results in an error on the order of 0.005. The established functions will be used to build a mite population model, but they should be generally useful to researchers who describe insect development and phenology.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.996

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A pheromone-based, mass-trapping system in a commercial plantation of 20-yr-old oil palm,Elaeis guineensisJacq., in Costa Rica, was used to assess changes in abundance and distribution ofRhynchophorus palmarum(L.) and the incidence of red ring disease. The spatial distribution of trapped adult weevils was analyzed using Taylor power law and Iwao regression technique from 243 traps over a 30-ha area, that were sampled at 1-mo intervals from September 1991 to January 1993. Both methods of regression provided a good fit of the data. Indices of aggregation indicated that the adult population was initially highly aggregated, but tended to become increasingly random as trap catch declined over time. Three-dimensional graphical depiction of trap counts from October to January over a 1-yr period illustrated that aggregation was concentrated at the periphery of the study site, suggesting high captures of immigrants. At the end of 17 mo of continuous trapping over the census zone,>62,500 weevils (≈94 per ha per mo) had been removed. Mean trap counts declined from 32.4 weevils per trap per month in the first 70 mo of trapping to 6.4 per trap per mo in the later 9 mo of trapping. Because trap catches remained uniformly low in the later interval and there was no indication of an expected rise in populations during the dry season (December-March) encompassed in this interval, it is likely that the mass-trapping effect was responsible [or maintaining the population at low density. After 5 mo of continuous trapping, monthly incidence of red ring disease in areas that trapped<20 weevils per trap per month declined to2 within the study site.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1005

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A study of azinphosmethyl and esfenvalerate runoff losses after application to sugarcane for control of the sugarcane borer was conducted on the St. Gabriel Research Station of the Louisiana State University Agricultural Center. In a 2nd study, leaf loads of these insecticides were determined. The 24-h LC50(27.8 μg/liter) of azinphosmethyl to bluegill was exceeded in 2 of the 9 runoff events that occurred during the study period, but because of expected dilution effects downstream from the site of application, only the concentration (261 μg/liter) that occurred in runoff 2 d after application was high enough to cause concern. The 24-h LC50(4,530 μg/liter) of azinphosmethyl to channel catfish fingerlings was not exceeded. The day 2 level of esfenvalerate (1.91 μg/liter) did not exceed sufficiently the 24-h LC50(0.42 μg/liter) of this insecticide with respect to bluegill to cause concern; the toxicity of the pyrethroid to channel catfish (2.35 μg/liter) was not surpassed. A reduced (two-thirds) rate application of esfenvalerate with acephate did not lead to concentrations of the pyrethroid in runoff higher than its toxicity to these fish species. The time to 50% disappearance (DT50) of azinphosmethyl leaf residues varied from 0.90 to 1.09 d, which was similar to the DT50(0.76 d) of the chemical in runoff. Esfenvalerate on leaves was longer lived (DT50= 2.46–4.46 d). These runoff and leaf residue data indicate that azinphosmethyl or esfenvalcrate applications to sugarcane should cause little concern for toxic effects on bluegill or channel catfish except possibly in the event of runoff within 2–3 d of application of the azinphosmethyl (possible bluegill toxic effects) or within 1 d of esfenvalerate application (possible toxicity to both fishes). Reduced rate applications would be of substantially less concern.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1013

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Frequency distribution of the citrus rust mite,Phyllocoptruta oleivora(Ashmead), damage on ‘Hamlin’ orange,Citrus sinensisfruit was studied from 24 August to 13 October 1993, in Lake Alfred, FL. The study plot consisted of 4-yr-old Hamlin orange trees, with a north-south row OIientation. Fruit on the north quadrant of the tree were found to have the highest mean surface damage, followed by the east, south, and west quadrants. The frequency distribution of fruit surface damage changed with mean damage levels. When the mean damage was low, most of the fruit had no rust mite damage. With increasing mean fruit damage, the proportion of fruit without damage decreased, and the proportion of fruit with higher damage correspondingly increased. The resulting frequency distribution changed from an exponential decay curve to a more or less symmetrical unimodal curve, with the peak shifting toward higher damage classes as mean fruit surface damage was increased. The frequency distribution was fitted to a 2-variable logistic distribution function of mean fruit surface damage and damage class, using maximum likelihood estimation method. Fruit without rust mite damage was considered a discrete point at zero, and its relative frequency was determined as the height of the cumulative logistic at zero. The model approximated the actual data well at low mean fruit surface damage, but gave a poor fit at high mean values.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1018

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Six studies were conducted to quantify the relationship between fruit surface damage of ‘Hamlin’ orange,Citrus sinensis, and population denisty of the citrus rust mite,Phyllocoptruta oleivora(Ashmead). Over time, the damage rate per mite-day increased in sigmoid fashion mainlyas a result of a sigmoid increase in cumulative mite-days. The sigmoid increase in cumulative mite-days resulted from the single-peaked, more or less symmetrically shaped mite population growth. Increasing fruit maturity increased susceptibility to mite feeding. This was indicated by a decline in mite-days required to cause a given percentage of surface damage as fruit maturity increased. Tree age and grove location did not seem to have obvious effect on the general trend in damage rate. A mathematical model was developed to describe the relationship between cumulative damage and cumulative mite-days. The model could be used to predict fruit surface damage based on mite population data.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1024

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The spatio-temporal dispersion patterns of adult leafhoppers (sampled with yellow sticky-boards)in deciduous orchards, apple,Malus silvestrisMiller, and nectarine,Persica vulgarisMiller, were studied using spatial autocorrelation statistics. Leafhoppers werc absent from the orchards before mid-May. Both,Asymetrasca decedens(Paoli) andEdwardsiana rosaeL., colonized the orchards followingthe blooming of trees. The 2 species were abundant in the apple orchard, producing 2 generations within the orchard.A. decedensdominated in the nectarine orchard, developing at least 1 generation within the orchard. Both species showed an aggregated spatial pattern at the edge of the orchards during the colonization wave. The spatial pattern ofA. decedensin both orchards changed from aggregated to random with each successive generation, and the population ofE. rosaemaintaincd aggregated pattems during the entire season. We suggest that the change in the aggregative pattern ofA. decedensresulted from the outward spread of the growing populations. Maintenance of the aggregative pattern byE. rosaewas probably related to both the outward spread of the population with each reproductive pulse and the successive colonization waves from the surrounding vegetation.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1032

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Predation of citrus red mite,Panonychus citriMcGregor, and citrus thrips,Scirtothrips citri(Moulton), by adult femaleEuseius tularensisCongdon was studied in laboratory experiments. Hungry predaceous mites readily attacked and fed on both species. Red gut coloration and distension of the gastric cecae persisted for 24—48 h after feeding on a citrus red mite deutonymph, depending on temperature (16.1—29.4°C), and for up to 14 h after feeding on a larva at 22.8°C. Isoelectric focusing electrophoresis (IEF) and staining for phosphogluco-isomeraseenzymes was used to study predation on citrus thrips larvae. Predation on an average size 2nd-instar citrus thrips could be detected for 16—40h after feeding, depending on temperature, and for up to 12 h after feeding on a 1st instar with the predator held at 22.8°C. IEF was used to evaluate levels of citrus thrips predation byE. tularensisin 15 field samples, 5 each taken from San Joaquin Valley, southern interior Califomia, and coastal citrus groves shortly after petal fall. Citrus thrips predation was indicated in only 7 of 556 adult femaleE. tularensissampled (1.3%). Contrary to popular belief, we question whether E. tularensis is a major factor in biologicalcontrol of citrus thrips. The IEF technique is also well suited for rapid screening of other potential citrus thrips predators.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1040

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Markov-recapture models obtain estimates of insect population size by concurrent operation of traps self-marking bait stations, with capture probabilities obtained from a Markov-process model of movement into the trap. Estimates are readily improved by repeating observations over time. However, a sequence of observations may reveal violated assumptions in ways not possible for a single observation, and it may not be possible to discern those violations from a fit of data. This article uses simulation to examine the effect of the following 5 types of violations: (1) using the estimate in an open population, (2) individuals are not uniformly catchable, (3) marking and trapping rates vary over time, (4) unequal response to marking stations and traps, and (5) behavior changes after marking. Individual catchability and behavior changes caused small biases, and were generally missed by a test of fit. All others could cause large biases. Among these, variation over time was easily discliminated by a test of fit. An open population mayor may not be discerned by a test of fit, and should be accepted or rejected on the basis of independent data. Finally, the rate violation is rarely picked up by a test of fit. It is suggested that it may be possible to estimate the parameters for the rate violation from the experimental data, and adjust the population estimate and confidence limits accordingly.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1052

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The biomass of dung beetles attracted to fresh cattle dung was studied in a Mediterranean holm oak pasture ecosystem with a continental Mediterranean climate (supramediterranean level). Results indicated a nonuniform biomass distribution of dung beetles throughout the year. Major peaks of species activity and biomass concentration of dung beetles occurred in open areas of the pasture in the spring followed by minor peaks in the fall. Beetle biomass in the open pasture was greater than that in the wooded pasture. The species of dung beetles comprising the greatest amount of biomass and the most important species available to destroy cattle dung pats in Mediterranean ecosystemswith a continental climate wereBubas bubalusOlivier,Onthophagus opacicollisd'Orbigny,Copris hispanus(L.),Copris lunaris(L.), andOnthophagus vacca(L.).

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1063

出版商:Oxford University Press    

年代:1995

数据来源: OUP