摘要:

Methods for estimating parameters of Holling's disk equation (=Michaelis–Menten function) were investigated mathematically and statistically. The sensitivity of each method to changes in variances was examined with computer simulation. The results showed that when error variances are proportional to the number of prey attacked, the Woolf transformation is effective in both linearizing the disk equation and reducing correlations between the variance and the mean, thus yielding the best estimates. When error variance is constant, nonlinear regression provides the best estimates. Under both circumstances, estimates by the proportional I (Holling's proportional method) and proportional II transformations are biased, because of correlated error terms. Estimates by the Lineweaver–Burk transformation have the least accuracy. Reanalysis of 22 data sets from the literature revealed that the Woolf transformation yielded better parameter estimates than nonlinear regression in 13 cases. Nonlinear regression yielded better estimates in two cases and tended to overestimate one of the parameters. The estimates of the other seven cases were similar between the two methods. We recommend that the Woolf transformation be used for estimating parameters of the Holling's disk equation instead of nonlinear regression.

DOI:10.1093/ee/23.4.785

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The distribution patterns of parasitized and nonparasitized potato aphids,Macrosiphum euphorbiae(Thomas), were assessed on four plantings of staked tomatoes from 1988 to 1990. Within plant distribution of nonparasitized aphids changed through the season, with the highest percentage of aphids found on the middle plant stratum during the first ≈60 d and on the upper stratum after this time. Aphid parasitism was inversely density dependent (i.e., rates of parasitism were highest on plantings with low overall potato aphid populations). In addition, parasitism varied within plants, with higher parasitism rates in the middle compared with the upper plant strata. Taylor's power law described an aggregated distribution pattern for both nonparasitized and parasitized aphids, regardless of leaf sample site used for analysis. Analysis of covariance for homogeneity of slopes indicated that the index of aggregation (b) from Taylor's power law remained consistent among years and among sample leaves. The third most recently expanded leaf from the uppermost of the plant (leaf T3) provided the highest relative level of precision among all single-leaf sample units for mean estimates at low aphid densities and was similar in precision to a sample unit consisting of the three uppermost leaves. A binomial sampling plan is presented that uses leaf T3 as a sample unit.

DOI:10.1093/ee/23.4.795

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The sawfly,Cephalcia arvensisPanzer, is a pest of the Norway spruce (Picea abiesKarst.) and has caused large outbreaks in Europe. The variability in the diapause length and the adaptability of the immature stages to a wide range of temperatures makes it difficult to predict the attacks and the phenology. In this paper, the effects of variable temperature regimes on both embryonic and larval development are studied in a natural environment. The experimental conditions covered the whole temperature range of the areas colonized by the pest. Several models were considered and their estimation were performed using the DEVAR software program applied to natural fluctuating temperatures. Before the application of DEVAR, its predictive power was tested using hypothetical data sets. The program was able to find parameter values leading to an excellent model fit. Four models were validated using data from three generations of natural populations of the pest. All models gave a good prediction for both embryos and larvae in all the years considered. The model can be usefully applied in population dynamics and in timing the application of both insecticides and entomopathogenic nematodes against the pest.

DOI:10.1093/ee/23.4.805

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

In insect sampling programs, decision making based oil intensity often reduces sampling time because inspection of a sample unit is terminated once an infestation is found. Sampling effort can be further reduced by using sequential binomial classification plans in which the sample size necessary to make a decision, with respect to an economic threshold, is based on preselected error rates and information gathered as sampling units are sequentially inspected. Commonly used insect sampling plans are derived from regression-based confidence interval procedures or hypothesis testing probability ratio procedures. The plans differ in their construction and use of decision thresholds, but operationally, they function and are interpreted in a similar manner. Therefore, statistical behavior of these plans, as measured by average sample number, terminal decision, and operating characteristic curves, are useful to compare relative performance. Decision criteria of three plans with comparable decision thresholds were applied to simulated presence-absence data of known binomial means to construct these curves. The curves differed among plans, and the greatest differences were in the vicinity of the decision threshold(s). When comparing operating characteristic curves, these plans differed in their approximation to the operating characteristic of an idealized plan which functions without error. A common plan modification requires decisions to be made when a maximum sample size is reached (i.e., a truncation mark). Relative differences among plans changed when the truncation mark was varied. Based on these simulations, general guidelines may be considered when choosing among plans.

DOI:10.1093/ee/23.4.812

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Field trials were conducted to determine the potential use of corn steepwater, an acid-hydrolyzed corn product, as a liquid bait for the Caribbean fruit fly,Anastrepha suspensa(Loew), in Florida. Preference tests compared relative attractiveness among aqueous solutions of standard torula yeast plus sodium borate pellets or 10% steepwater (vol:vol) plus 1, 3, 5, and 10% (wt:vol) borax in traps. Total number of females trapped decreased from 474 in fresh bait solution to 197 and 154 in 2–3-d old and 4–6-d old bait solutions, respectively. When freshly prepared solutions were tested, the torula yeast-borax solution was the most attractive and the 10% steepwater with 1% borax the second most attractive bait formulation, capturing 45 and 23% of the trapped females, respectively. After 2–3 d of field-use, there was less discrimination among the baits, although the 10% steepwater with 1% borax and with 10% borax each captured 29% of the trapped flies. By the last 4–6 d of field use, the 10% steepwater with 1% borax was most preferred and captured 45% of the trapped flies. Dissections of subsamples of trapped females indicated that only 50% of the females from tortula yeast-borax traps were unmated, while 80–95% of the females caught in any of the steepwater traps were unmated. The addition of 1, 3, 5, and 10% borax increased the initial pH of the acidic steepwater to 5.95, 7.76, 8.44, and 8.76, respectively. The relative attractiveness of the 10% steepwater with 1% borax increased as this bait approached a neutral pH over the 6 d of field use.

DOI:10.1093/ee/23.4.827

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The impact of sticky trunk barriers on the density of larval gypsy moths,Lymantria dispar(L.), in oak (Quercusspp.) trees with isolated and contiguous canopies was studied. Measurements of frass drop per unit of area and frass yield per larva were used to estimate larval density. The trunk barriers reduced larval density by an average of ≈27%. The effect of the trunk barriers was the same on isolated- and contiguous-canopy trees on the first sample date, when larvae were predominantly fourth instars. On the second sample date, when larvae were predominantly fifth and sixth instars, the effect of trunk barriers on larval density was greater on contiguous-canopy trees. These results indicate that reinfestation of trees from the canopy of adjacent trees is minimal at low to moderate gypsy moth larval densities (up to ≈80 larvae per square meter). Defoliation levels and subsequent egg-mass density were not affected by trunk barriers. While sticky trunk barriers appear to consistently reduce larval density on both isolated- and contiguous-canopy oak trees, they do not provide adequate foliage protection. Frass drop (number of frass pellets per square meter) was the most sensitive measure of treatment effects. The estimation of larval density by incorporating information about frass yield per larva introduced additional variability which made this a less sensitive measure of treatment effects.

DOI:10.1093/ee/23.4.832

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Larvae ofHelicoverpa zea(Boddie) fed on a meridic diet containing silks of a resistant corn genotype, ‘Zapalote Chico 2451# (PC3)’, were examined as suitable hosts for a larval–pupal parasitoid,Archytas marmoratus(Townsend), and a pupal parasitoid,Ichneumon promissorius(Erich). Host pupal weight, parasitoid weight, and developmental time were significantly reduced when host larvae were reared on a diet containing resistant silks compared with diet without resistant silks. Weight ofA. marmoratuswas strongly correlated with host weight for both host diets. Parasitoid developmental time for both parasitoids was also correlated with host pupal weight for hosts fed on a diet containing resistant silks. Fecundity of both parasitoids was not affected by host diet. Adult longevity ofI. promissoriuswas significantly reduced when reared from hosts fed the diet containing resistant silks compared with hosts reared on the diet without resistant silks. Longevity of femaleA. marmoratuswas not affected by host diet, but maleA. marmoratuslived longer when reared from hosts fed the resistant diet. Despite a few negative effects (lower percentage emergence ofA. marmoratus) of a resistant host diet on the parasitoids, these strategies could be compatible because the negative effects did not result in lower parasitoid fecundity or increased parasitoid developmental time.

DOI:10.1093/ee/23.4.837

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The relationships between temperature and rates of development of eggs and larvae for the pine false webworm,Acantholyda erythrocephala(L.), were determined at constant temperatures in the laboratory. Observed mean development times of eggs ranged from 35.8 d at 10.7°C to 8.2 d at 26.7°C. Some egg development took place at temperatures between 3.9 and 7.0°C, but the eggs failed to hatch. Interpolation techniques were used to predict development times at these low temperatures. Mean developmental times for larvae ranged from 75.5 d for females at 7.3°C to 13.9 d for males at 29.0°C. Average development times of females were greater than those of males at all temperatures. Models incorporating the relationships between temperature and development rates of eggs and larvae were constructed to simulate the development of these arboreal stages under field conditions. Model predictions were compared with field observations of egg hatch and larval drop using temperatures recorded in meteorological shelters, plantation canopies, and larval webs as model inputs. Air temperatures recorded in a plantation canopy provided the best prediction of egg hatch, which suggests that egg development was not greatly affected by direct solar radiation. Average temperatures within larval webs were as much as 2.4°C warmer than ambient air temperatures. Using air temperatures as model inputs resulted in deviations of<3 d between observed and predicted times of larval drop from the branches to the ground. The use of canopy temperatures as inputs slowed predicted development and increased the deviations between observed and predicted larval drop. Using web–temperature corrections for models of developing larvae reduced these deviations, but did not provide as accurate predictions as air temperature alone.

DOI:10.1093/ee/23.4.846

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Fifth instars of the hemipteran predatorPerillus bioculatus(F.) were observed as they attacked neonateLeptinotarsa decemlineata(Say) larvae on potato plants. Observations were conducted at prey densities ranging from one to 100 prey per plant, and standard functional response models were fit to the predation rates obtained. Neither the type II nor the type III functional response curves provided a satisfactory fit to the data. The observed attack rate was neither constant over all prey densities (as in the type II model), nor an increasing function of prey density (as in the type III model). Instead, it declined over prey densities from one to 25 and then increased substantially at the density of 50. A possible explanation for the observed pattern is that area-restricted search following prey consumption led to additional successful feeding events at high densities but not at low densities. The mean observed handling time was essentially equal to an estimate based on the type III model and prey density did not have a Significant influence on per-prey handling times.

DOI:10.1093/ee/23.4.855

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The presence of russet body coloration inNezara viridula(L.) has been used as an indicator of reproductive diapause. Our studies have shown that this coloration is not a reliable indicator of diapause. Russet coloring was not found in all reproductively diapausing adult females, whereas some direct developing females exhibited russet coloration. Diapausing females that developed russet coloring did so sooner after eclosion than those that developed directly. Diapausing individuals also had a greater proportion of their body russet colored than nondiapausing individuals. Possible reasons for the increased prevalence of russet colouration in diapausing adults are discussed.

DOI:10.1093/ee/23.4.860

出版商:Oxford University Press    

年代:1994

数据来源: OUP