摘要:

Five clones of the willow,Salix exiguaNuttall, along the Weber River, Utah, produced shorter shoots with increasing ramet age. The number of ovipositions by the shootgalling sawfly,Euura exiguaeSmith, correlated positively with shoot length, so that sawfly density was high on younger ramets of a clone and low on older ramets. The sawfly attacked the most vigorous parts of the clones. Survival of progeny in galls decreased with ramet age from 60% survival on 1-yr-old ramets to 26% survival on 6-yr-old ramets when plant-induced mortality was considered alone. The effects of parasitoids on the pattern of sawfly attack was not significant. Survival of progeny in young ramets (2 and 3 yr old) was higher in the egg to very early first-instar stage (50%) than in older ramets (37%) (5 and 6 yr old), but differences were slight after that stage. The major determinants ofEuurapopulation distribution on willow clones were the female selective oviposition behavior on longer shoots on younger ramets, which probably evolved in response to higher survival of progeny in the younger ramets. When the relative effects of attack and survival were evaluated in response to ramet age, age accounted for 89% of the variance in attack and 95% of the variance in survival. The contrast between this species and others that attack vigorous plants and plant parts and those that attack stressed plants is emphasized, and an explanation is proposed for the difference between epidemic pest insect herbivores and those that remain as endemic species.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.61

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Lesser cornstalk borer (LCB),Elasmopalpus lignosellus(Zeller), populations were monitored for 3 yr in commercial peanut,Arachis hypogaeaL., fields in an intensively cultivated area of Comanche County, Tex. Population census raw data were standardized to make LCB density estimates comparable among generations and years. Partial ecological life tables were constructed from standardized census estimates for five pivotal stages: eggs, just-hatched larvae, medium larvae, large larvae, and pupae. Mortality factors were classified as parasitism, disease, and unexplained. Identified mortality agents included an entomopoxvirus, a fungus, 13 primary parasites, and five predators. Survivorship curves implied a constant mortality rate with total generation mortality ranging from 87.1 to 96.5%. Keyfactor analysis revealed unexplained mortality was the major contributor to overall mortality, with unexplained mortality of large larvae the key mortality factor. Three methods of analyzing mortality–density relationships showed mortality was density independent, with initial egg density rather than mortality determining the resulting larval and pupal population densities.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.69

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The leaf beetleTrirhabda bacharidis(Weber) is the dominant herbivore of the woody shrubBaccharis neglecta(Britt.) in central Texas. Eggs were deposited in clusters on the base of the main stem of the plant from April to June and remained dormant for 7–10 mo. In 1984 and 1985, mean populations of 91 and 572 neonate larvae per plant, respectively, were found in late winter from eggs deposited on the base of main stems. Larvae often defoliated the plant. Mature larvae dropped or crawled to the ground in March and April and pupated in the soil. Mean adult populations of 154 and 239 beetles per plant emerged in April 1984 and 1985, respectively; they also defoliated some plants. Laboratory reared females deposited a mean of 517 eggs each. Host specificity tests were conducted with larvae ofT. bacharidison 12 species of Asteraceae. Mean larval consumption was 1,915, 1,162, 692, and.678 mm2of leaf tissue per larva onBaccharis halimifoliaL.,B. neglecta,B. sarothroidesGray, andB. pilularisDC., respectively. Larval development required 26–29 d. Adults were tested on seven species ofBaccharis; they preferred the same four plants as did the larvae. Larval and adult consumption, pupal weight, and adult longevity were greatest onB. halimifolia.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.78

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The European corn borer (ECB),Ostrinia nubilalis(Hübner), is a major pest of corn in many countries. To quantify borer losses, a model describing development of the five instars of ECB for a single generation of development, tested on data collected at INRA-Versailles, France, is proposed and discussed. It consists of two parts: a degree-day model that takes into account the influence of temperature; and normal distributions that represent the variability of population development time among instars. A method of estimating the parameters of this model for field data by maximum likelihood is described. This statistical approach showed how the experimental design should be improved. For the six climatic sequences recorded, this simple model is an appropriate representation of development of the four instars sampled with enough accuracy. A validation of the model supports this conclusion. The chosen model is based on simple biological hypotheses and can be fitted under field conditions. The advantages of these two characteristics lies in the possibility of comparing laboratory and field estimations, to analyze their differences, and to determine under which environmental conditions the model is correct (i.e., validity area).

ISSN:1754-5692    

DOI:10.1093/ee/18.1.85

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Seed losses to the Douglas-fir cone gall midge,Contarinia oregonensisFoote, and Douglas-fir seed chalcid,Megastigmus spermotrophus(Wachtl), were measured in a Douglas-fir,Pseudotsuga menziesii(Mirbel) Franco, clonal seed orchard and in a Douglas-fir progeny plantation in western Oregon. Seed losses to both insects differed significantly (P<0.05) among clones and among the progeny of selected parental crosses. Seed loss differed more than three times between least-infested and most-infested clones or progeny. Seed losses in the progeny plantation indicated that resistance to these two insects is a heritable trait, with greater resistance showing a tendency to dominate over lesser resistance. Insect responses to host genotype may be modified by factors associated with the position of the tree within the stand. Implications of these results for tree improvement programs and seed orchard management are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.94

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Differential screening techniques and pitfall trap monitoring of dung fauna were used to evaluate some biotic mortality factors of the immature stages of the horn fly,Haematobia irritans(L.), in cattle dung pats on an unimproved east-central Texas pasture. Exposure to dung fauna caused an average of 87.9% mortality to immature horn flies in naturally infested dung pats in tests conducted weekly from April to mid-September. Horn fly mortality in artificially infested dung pats during the same period averaged 93.1%. Indirect correlations were shown between numbers of scarabs and predaceous insects collected in pitfall traps and horn fly mortality in exposed dung pats. Direct correlations were found between pitfall trap collections of predaceous insects and horn fly mortality in dung pats covered with scarab excluder cages. Predation and scarab activity were about equally important as mortality factors of the horn fly at this location. Predation accounted for most of the horn fly mortality from April until mid-June, and scarab activity was the most important mortality factor from July until the tests were discontinued in mid-September.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.98

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The Mediterranean fruit fly,Ceratitis capitata(Wiedemann), was reared at four larval densities in mature green, color break, and ripe coffee from Manoa and Makaha Valleys, Hawaii. Most eggs hatched within 48–72 h in coffee fruit and were unaffected by ripeness or location. Larval survival was generally related to larval density and coffee maturity. However, there were significant (P<0.05) interactions in larval survival, larval and pupal development times between site, and berry maturity. The weight of coffee berries varied with maturity and location. Flies reared on Makaha berries were significantly (P<0.05) more fecund than flies reared on Manoa berries. Net reproductive rates showed doubling times of 43 and 13 d, respectively, for Manoa and Makaha flies.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.103

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Fifty-two lines ofAcyrthosiphon pisum(Harris), the pea aphid, from three Australian locations did not produce oviparae and only one female produced males when reared at short photoperiods and low temperatures. We conclude that sexual reproduction is not common among Australian pea aphids. Fundatrix-like aphids with short appendages were collected from field populations in the spring. These were not true fundatrices, because it is unlikely that they hatched from sexually produced eggs. Samples of aphids from lucerne (alfalfa) showed that the relative length of appendages increased through the spring and early summer and decreased in the late summer and early autumn. When reared at room temperature with a long photoperiod, the offspring of fundatrix-like aphids had longer appendages than their parents and the length of the appendages increased in succeeding generations. Aphids reared at low temperatures with short photoperiods from before birth had reduced appendages. We conclude that environmental factors can affect the relative length of appendages in anholocyclic populations of the pea aphid.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.111

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Arthropod predators of velvetbean caterpillar,Anticarsia gemmatalisHübner, eggs and larvae were determined using a direct observation technique. Observations of predation events were made on soybean foliage and the ground below the foliage. Predation on eggs and three size classes of larvae is presented as proportional seasonal consumption over 14 to 16 h by each arthropod predator species. On the foliage,Spanogonicus albofasciatus(Reuter) (Hemiptera: Miridae) andGeocoris punctipes(Say) (Hemiptera: Lygaeidae) were observed eating velvetbean caterpillar eggs in 1981. For small velvetbean caterpillar larvae,Tropiconabis capsiformis(Germar) (Hemiptera: Nabidae) was the major consumer in 1981, whereas in 1982,G. punctipes and Calleida decora(F.) (Coleoptera: Carabidae) were the major consumers. For medium and large velvetbean caterpillar larvae in 1981, tettigoniids (Orthoptera) consumed the largest proportion. On the ground, the antPheidole morrisiForel (Hymenoptera: Formicidae) was the major consumer of all three size classes of velvetbean caterpillar larvae in 1981. In 1982, the earwigLabidura riparia(Pallas) (Dermaptera: Labiduridae) ate the greatest proportion of small velvetbean caterpillar larvae on the ground.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.118

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Sixty-eight individually markedMonochamus carolinensis(Olivier) were tethered for flight on the day of emergence and weekly thereafter for 5 wk. The percentage of beetles exhibiting flight was independent of sex and age. The two longest flights, 72.5 and 69.4 min, were recorded for males; however, there was no difference in mean flight duration between sexes. The longest mean flight duration, 15.4 min, occurred for beetles 1 wk after emergence.

ISSN:1754-5692    

DOI:10.1093/ee/18.1.124

出版商:Oxford University Press    

年代:1989

数据来源: OUP