摘要:

The probability of a bark beetle infestation starting and growing in any given stand of trees is termed stand risk. This probability is defined by a conceptual model that describes the functional relationship between beetle population size and the physiological condition of the stand of trees. The relationship is dynamic, so that changes in either insect population levels or stand condition result in changes in risk. Stand risk approaches zero when stands are in good condition or beetle populations are very low. The risk increases in a logistic fashion as insect populations increase or stand conditions decline, and it is asymptotic for a probability approaching 1. The model incorporates a threshold concept for stand risk and can be integrated into population dynamics models to assess future risk.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.619

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Heliothismight be managed effectively by directing control measures at the first generation in spring weed hosts. During the spring, the total population is relatively small and occupies a much smaller acreage than in July, when conventional control practices are initiated. Substantial population reduction in April and May might retard population growth to the extent that economic thresholds in cotton might not be reached until much later in the season, thereby reducing insecticide costs and overall insecticide input. Two potential flaws in this theory relate to questions concerning the origin of springHeliothispopulations and possible large-scale moth immigration in spring and/or summer. In addition, certain control measures initiated in the spring could be more detrimental to predators and parasitoids than toHeliothisand thus diminish the regulatory abilities of natural enemies. Various control tactics are discussed with reference to their likely impact onHeliothisand its natural enemies.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.625

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Multiple-comparison procedures for comparing means, medians, or proportions are commonly used by entomologists publishing in ecological and agricultural journals of the Entomological Society of America. Unfortunately, there is confusion among many researchers and reviewers with respect to the type I error rates of the various tests. The calculation of and reasoning behind the error rate and relative conservativeness or liberalness of each test are discussed. Several guidelines concerning use of these tests are proposed, including specification of which test was used and why, and a recommendation encouraging a switch to the use of confidence intervals instead of hypothesis tests. It is felt that adoption of these and other proposals for reporting results will increase the meaningfulness and scientific merit of published entomological research.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.635

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

MaleAnastrepha suspensa(Loew) produce two female-directed sounds, the calling and precopulatory songs. Aspects of these were correlated to factors thought important in male sexual success and compared in males that copulated and males that failed to mate. Both sounds became more intense with male size. Larger males tended to have calling songs of lower fundamental frequency, but frequency of precopulatory songs and size was uncorrelated. The calling song's fundamental frequency bandwidth was broader in unsuccessful flies, perhaps reflecting physical disability. Precopulatory songsmay be the last acoustic opportunity for males to demonstrate their “quality” and receive further cooperation from females they have mounted. Unsuccessful precopulatory songs were not as loud and had a broader bandwidth than successful songs. Greater distortion in unsuccessful songs appeared to be due to female movement during rejection. The longer a precopulatory song, the shorter the subsequent mating. This may have been due to males making greater efforts toward less sexually responsive mates. Larger males coupled longer, suggesting a potential conflict of interest between the sexes over copulation duration that bigger males are more apt to win.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.650

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Density and survivorship of solitary and coexisting populations ofPineus boerneriAnnand andPineus coloradensis(Gillette) (Homoptera: Adelgidae) were studied for 3 years in 12 stands of red pine,Pinus resinosaAiton, in Connecticut and Rhode Island. Survival ofP. boerneriwas higher on branches than on needles during winter but higher on needles than on branches during spring and summer. Survival ofP. coloradensiswas always higher on needles than on bark. The percentage of branches that were resinous (indicative of injury) increased at four coinfested pine stands from 1980 to 1982. The proportion of theP. boerneripopulation on needles relative to bark increased during that period; the opposite trend was observed forP. coloradensis. Decreasing density ofP. coloradensison needles was related to increasing density ofP. boerneri, and was due to a combination of greater mortality on needles and greater colonization of bark, where chance for survival was even less.P. boerneriestablished and maintained numerical dominance overP. coloradensisin these four coinhabited pine stands and on pine seedlings in the greenhouse.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.657

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Laboratory studies investigated the effects of weeds associated with reduced tillage in corn on a major black cutworm parasitoid,Meteorus rubens. Adult female wasps provided with any of five flowering weed species lived longer, attacked more hosts, and produced more offspring than those lacking a food source. In addition, wasps maintained on a combination of three weed species in flower lived longer than those given nonflowering plants of the same species or no food source. These results demonstrate that flowering weeds associated with reduced tillage in corn are beneficial toM. rubensas nectar sources.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.664

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

We tested the hypothesis that increased prey availability, which results in increased energy consumption and probably lower energetic costs of foraging, increases reproductive output. Larvae ofMetasyrphus corollae(F.) (formerlySrphus corollaeF.), which are obligate predators of aphids, were individually reared at 19.5 ± 1°C, with 10, 20, 40, or 60 pea aphids offered each day on plants with a surface area of 7.5, 35, or 73 cm2. When more aphids were offered, larvae consumed more and produced heavier pupae. Fecundity of adults reared from these pupae was extremely variable (range, 0–1,488 eggs laid) and depended mostly on adult longevity, not on consumption or pupal weight. More eggs were laid in the first 15 days of adult life by larger adults. Adult longevity depended on the size of the cage in which the adults were kept. Flight had a higher cost against reproduction in small fliesthan in large ones. Differencesbetween the strategy of energy allocation of insects which acquire most of their energy while they are larvae and that of insects which feed while reproducing are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.669

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

SmallAgromyza frontellafemales (800 µg) females. Experiments testing the efficacy of aqueous abdomen extracts from large females with different histories of feeding activity and from females of different sizes, together with comparisons of both feeding and marking behavior of large and small females, provided strong evidence that this difference is due to the quantity of pheromone deposited because: (i) ODP production byA. frontellais directly related to feeding activity, (ii) small females feed and mark significantly less than large ones, and (iii) the acceptance or rejection of marked leaflets follows a dose-dependent response. The possible ecological implications of such differences in pheromone production are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.675

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Under greenhouse conditions there is a direct relationship between the density of glandular trichomes on aphid-resistant potato clones (Solanum tuberosumxS. berthaultii, F3andS. berthaultii) and the adverse effectson 11 aphidophagous species. These negative effects include a reduction in adult coccinellid searching time, a decrease in the distance newly hatched chrysopid and coccinellid larvae move, and a decrease in the number of eggsChrysopa oculataoviposit on highly pubescent foliage. Survival of the parasitoidAphidius matricariaedecreases when adults are exposed to moderate and high densities of glandular pubescence. However, the severe negative effects observed under greenhouse conditions are attenuated in the field. Field studies show that natural enemies and moderate levels of glandular pubescence are compatible mortality factors in the management of aphids on potatoes. Thus, although these greenhouse and laboratory studies elucidate the behavioral responses of natural enemies to glandular trichomes, they inadequately predict the effects of glandular pubescence on beneficial insects in the field.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.679

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Management programs for the apple maggot (AM),Rhagoletis pomonella(Walsh), were tested in small orchards of dwarf and semi-dwarf, disease-resistant apples in New York State. These orchards were exposed to severe AM pressure from nearby unsprayed apple and hawthorn trees. In the Hudson Valley, a standard six-spray schedule of azin-phosmethyl applied every 14 days from June to mid-August reduced AM damage to 1.4% in 1979, and in 1980 a reduced two-spray schedule of azinphosmethyl at the beginning and peak of adult activity gave similar control (1.3% damage). In an adjacent plot, a nonconventional control program of trapping AM flies on red sticky spheres was about as effective (1.0% damage) as the azinphosmethyl program in 1979, but allowed more damage (4.9%) in 1980 than the reduced insecticide schedule. At Geneva, plots treated with carbaryl starting 10 days after AM emergence and thereafter at 14-day intervals during adult activity had 5.7 and 0.4% infested fruit, respectively, during 1980 and 1981. Carbaryl applications in other plots based on Pherocon AM trap catches or fruit maturation were less effective. Sphere trapping programs at Geneva which had 12.8 and 2.9% infested apples, respectively, during 1980 and 1981, were also slightly less effective than the standard protective carbaryl schedules.

ISSN:1754-5692    

DOI:10.1093/ee/13.3.684

出版商:Oxford University Press    

年代:1984

数据来源: OUP