摘要:

An earlier forum article identified a need for new analytical methods for obtaining stage-specific estimates of losses from parasitism for life table, population dynamics, and evaluation studies. A discussion of the conceptual framework for recently developed solutions to this problem is presented. Classes of solutions considered include recruitment, stage frequency, and death rate analyses. We present the rationale and methodology for each and compare their relative usefulness for systems of varying types of biologies and sampling constraints. These solutions provide tools for the more accurate quantification of parasitism as a mortality factor in insect life systems

ISSN:1754-5692    

DOI:10.1093/ee/20.1.1

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

European corn borer,Ostrinia nubilalis(Hübner), egg hatch was studied under several temperature and humidity regimes. Percentage of hatch was severely decreased, regardless of the humidity, at 36 and 39°C. Hatch ranged from 74.0 to 0.5% at vapor pressure deficits of 7.5–32.5 mb over the temperature range of 24–33°C in 3°C increments. European corn borer egg hatch was affected similarly, from oviposition to larval eclosion, by a 12-h stress period of 14.5, 17.5, and 20.5 mb (at 30°C). Two separate aspects of the egg chorion or two processes in egg hatch are hypothesized to be disrupted by the stressful conditions as evidenced by three plateaus in percentage of eggs hatching as the length of exposure to stress increased. Percentage of hatch remained relatively stable at about 68% with exposure to 33.9-mb stress for ≤24 h. As the length of stress increased to 36–60 h, the percentage was about 22%. The percentage of hatch fell to only 2.7% at 72 and 84 h of consecutive exposure. Finally, the effect of environmental conditions on egg hatch was additive whether the eggs experienced constant stress or experienced periods of stress alternated with periods of moderate conditions. Results of this study suggest that environmental stresses (i.e., “stress units”) may accumulate and affect survival of European corn borer eggs in a manner analogous to temperature units and insect development.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.8

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Aggregation behavior was elicited in both sexes of the green June beetle,Cotinis nitida(L.), when green June beetle males fed on peach slices inoculated with one yeast species,Trichosporon cutaneum(de Beurm. Gougerot et Voucher) Ota. Peach puree monocultures were made by inoculating sterile peach puree with one of three yeasts (Aureobasidium pullulans(de Bary) Arnaud,Candida krusei(Castellani) Berkhout,C. tropicalis(Castellani) Berkhout), which were all endemic flora isolated from the feces and gut of green June beetles collected from feeding aggregations on unsterile peaches in the field (natural bait). In a field bioassay, peach puree monocultures ofC. tropicalis(in experiment A) andC. krusei(in experiment B), both without beetle feeding, were significantly more attractive (P<0.05) to both sexes of green June beetles than sterile peach puree with or without beetle feeding, but all peach purees were significantly less attractive than the most attractive natural bait. In experiment C, peach slices were inoculated with either of two yeasts (biovars A or B ofT. cutaneum), which were the predominant isolates from the gut of laboratory-reared green June beetles fed on unsterile peaches. These monocultures ofT. cutaneumon peach slices without beetle feeding were relatively as attractive as monoculture-inoculated peach puree alone containing one of the three other yeasts noted above. But when laboratory-reared green June beetle males previously fed on theT. cutaneum-inoculated peach slices were included with these peach slices, the bait containing biovar A was as attractive as the natural bait. Although the bait of laboratory-reared green June beetle males feeding on peach slices inoculated with biovar B was significantly less attractive (P<0.05) than the natural bait, it was Similarly attractive to the laboratory-reared green June beetle males feeding on the biovar A-inoculated peach slices. The laboratory-reared green June beetles required a period of 1 d or more of feeding on yeast-inoculated fruit to achieve peak production of aggregation semiochemical.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.15

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Emergence and developmental rates of nondiapausing pepper maggot,Zonosemata electa(Say), pupae, reared from naturally infested pepper (Capsicum annuumL.) and horsenettle (Solanum carolinenseL.) fruit, were compared at seven constant temperatures: 5, 10, 15, 20, 25, 30, and 35°C. Pupae originating from pepper had significantly greater pupal weights and percentage of adult emergence than pupae from horsenettle. However, host plant origin, color, sex, and weight had little influence on pupal developmental times across temperatures. Nonlinear and linear models were fit to the temperature versus developmental data and used to predict adult emergence in the field. A nonlinear, four-parameter, poikilotherm model, fitted (r2= 0.99) to median development rates of pepper and horsenettle pupae combined, indicated that development was linear between 10 and 25°C, optimal at 26°C, and dropped to near zero at 35°C. The lower developmental threshold (± SE) for horsenettle- and pepper-reared pupae combined (9.33 ± 0.09°C)was determined by linear regression and thexintercept method. Completion of pupal development for the combined sample required 602 ± 13 degree-days (±SE) above the base temperature. Contrary to previous reports, phenology of adult pepper maggot in the field was unaffected by host plant origin. A degree-day model incorporating a 9.5°C developmental threshold and soil temperatures (10 cm depth) accurately predicted (±l d) the 50% emergence points (E50) of adults reared from both host plants. A stochastic simulation model, incorporating a nonlinear developmental rate function and 2-h soil temperature records, also predicted the E50point accurately (±1.5 d). The simulation model accurately predicted the E5and E75to E100points, making it useful in management situations where emergence percentiles other than 50% are required.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.22

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

A commercial formulation ofBacillus thuringiensisvar.kurstakiBerliner (Dipel 2X) and purified HD-73 delta-endotoxin were evaluated for effects on the growth, behavior, and fitness of susceptible and toxin-adapted strains ofHeliothis virescens(F.) by incorporation of the materials into artificial diets at varying concentrations. Neonate larvae were placed in experimental arenas where they could choose a diet containing toxin and a control diet, or were placed in arenas where the only diet available contained a toxin. The difference between the strains in growth and survival was much more pronounced when larvae could not choose to feed on the control diet. Both strains avoided moderate and high concentrations of the toxins. At the lowest concentration of HD-73, neither strain avoided the diet that contained the endotoxin. At the two lowest concentrations of Dipel 2X, only the susceptible strain avoided the diet containing Dipel. Data on growth rate, survival, and fecundity of the two strains reared on HD-73 delta-endotoxin were used to set parameters of a Single-locus genetic model to predict the rate at whichH. virescenspopulations would adapt toB. thuringiensisvar.kurstakior its endotoxin when exposed to it in choice and no-choice situations. Results from the model generally predict much more rapid adaptation in no-choice situations.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.30

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The survival of Africanized honey bees,Apis melliferaL., in temperate regions was evaluated in Germany during the 1988–1989 winter. Africanized, local European, and Africanized × European colonies were started by queen introductions on 5 August, and all surviving colonies were depopulated on 21 February. Five of nine Africanized colonies had died by the end of the experiment, whereas all eight European and all five Africanized × European colonies survived. Brood production of the three genotypes declined from 18 August until 13 November with significant differences on two of the seven measurement dates. Brood areas were not different among surviving colonies that had resumed brood production by 21 February. Changes in total colony weights through time were not different. Significant differences were found in the rates of colony weight loss (kilograms total weight/average kilograms of adult bees∗time)and in final adult population size. The higher attrition of worker populations and the higher mortality of Africanized colonies suggest a possible reduction of their adverse effect as their range expands northward to temperate areas in the United States. The intermediate values for all characters in the Africanized × European colonies suggest that genes underlying overwintering characters are additive. This additivity will permit different levels of hybridization for different ecological zones, thus complicating predictions about absolute climatic limits.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.39

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The effects of cold period duration and simulated rain on adult apple maggot,Rhagoletis pomonellaWalsh, emergence were investigated under laboratory conditions. Pupae were exposed to cold periods ranging from 9 to 191 d. There was no adult fly emergence from pupae exposed to ≤23 d of cold. The degree-day (6.5°C threshold) requirements for first and 50% emergence increased for pupae exposed to cold periods ranging from 37 to 65 d; however, flies exposed to longer cold periods (79–191 d) required fewer heat units for emergence. The effect of simulated rain (2 cm) on adult emergence was tested at various degree-day accumulations (677–1,065) during pupal development. Pupae exposed to rain at any of the degree-day accumulations tested required significantly fewer heat units for first and 50% emergence, compared with pupae not exposed to rain.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.44

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The pales weevil,Hylobius pales(Herbst), and the pitch-eating weevil,Pachylobius, picivorus(Germar), are part of a weevil complex causing extensive damage to plantation pines throughout the Lake States. A means of monitoring weevil populations has been developed using pitfall traps baited with ethanol and turpentine. The relative attractiveness of six combinations of ethanol and turpentine were compared. Traps were monitored throughout the 1988 and 1989 growing seasons in a Scots pine Christmas tree farm. Both species were more strongly attracted to ethanol/turpentine ratios above 1:1. Pales weevils preferred slightly higher ethanol/turpentine ratios than did pitch-eating weevils. Within species, both sexes responded equivalently among treatments. The implications of these behavioral responses to weevils' locating stressed trees, the role of chemical ecology in niche partitioning, and IPM of pine root weevils are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.48

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Theα-amylase inhibitor content in saline extracts of 104 Eastern soft wheat cultivars was determined by assay against a purifiedα-amylase preparation from the rice weevil,Sitophilus oryzae(L.). A two-fold range of inhibitor levels, expressed as amylase inhibitor units per gram of dry weight (AIU/g), was found across all cultivars. Inhibitory activity was lowest in cultivar ‘Augusta’ (5,084 ± 124 AIU/g) and highest in cultivar ‘Logan’ (10,410 ± 61 AIU/g). No correlation of inhibitor content with progeny production (r= −0.161) or rate of emergence (r= −0.292) was found among weevils reared on 30 cultivars having relatively low, medium, and high inhibitor levels, but there was a positive correlation between inhibitor content and average number of days to adult emergence (r= 0.569). Although mean development times were significantly different on cultivars with low and high AIU/g (35.9 ± 0.2 and 36.6 ± 0.1 d, respectively), the differences were only slight and indicated that, for these cultivars of soft wheats,α-amylase inhibitors have little practical effect on initial population reductions. Nevertheless, based on a population model forS. oryzaedeveloping on wheat at 25°C and 75% RH, the slight delay in mean development time (0.7 d) on cultivars with relatively high AIU/g results in a 20.9% reduction in total number of weevils after 180 d. Simulations also indicate that physical or biochemical resistance factors in wheat have to delay development time for about 6.2 d or reduce fecundity by about 40%to prevent wheat from being graded “weevily” 180 d after a single pair of weevils infests a hypothetical 6,000-bushel wheat bin.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.53

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Developmental times for the immature stages of four species of endoparasitoids ofHeliothis virescens(F.),Microplitis croceipes(Cresson),M. demolitorWilkinson,Cotesia kazak(Telenga), andHyposoter didymator(Thunberg), were studied at 20, 23, 25, 27, 30, 32, and 35°C. The responses ofM. croceipesandH. didymatorto increases in temperature were significantly different from each other (P0.05;F= 0.58; df = 1, 18). The developmental temperature optima were 33°C forM. croceipes, 31°C forC. kazakandM. demolitor, and 29°C forH. didymator.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.61

出版商:Oxford University Press    

年代:1991

数据来源: OUP