摘要:

Ecological data on a native gall-forming midge,Rhopalomyia californicaFelt (Diptera: Cecidomyiidae), and its parasites in California are used to determine the “best” species or combination of species of parasites to introduce for control of the midge in an imaginary country whose climate is similar to that of the Sacramento Valley of California. Over 4,000 combinations (introduction strategies) among the 12 species of parasites were possible. There was no one “best” species or combination of species in this case; instead, several introduction strategies appeared to be good risks. The results suggest that, where several species of candidate natural enemies are available, several introduction strategies will also exist. After almost 100 years of practice in classical biological control, an adequate theoretical framework for assessing multiple-species introductions is generally lacking. Thus, some of the major theoretical problems in classical biological control remain to be solved.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.525

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

Methods of estimating the probability of encounter and probability of parasitism given encounter are described for situations in which a host patch that has not been encountered by a parasitoid cannot be distinguished from one that has been encountered but none of the hosts have been parasitized. These methods provide estimates of quantities which do not vary with host density per patch unless parasitoid behavior changes, and therefore are the appropriate ones to use to detect effects of host density on the intensity of parasitism. An example is given, using published data on the parasitism ofHeliothis zeaeggs byTrichogrammaspp.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.531

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

The population dynamics of three soybean herbivores,Heliothis zea(Boddie),Epilachna varivestisMulsant, andPopillia japonicaNewman, are discussed with relation to agroecosystem structure. Specific effects examined include climatic variations, spatial structure, temporal structure, cultural practices, and socio-economic changes. A discussion of the need for more comprehensive modeling efforts is also included.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.538

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

Pest populations are frequently regulated below their potential levels of abundance by natural enemies, host resistance, or other biological interactions. However, if these regulating processes operate imperfectly, or are intolerant to variations in pest density, then we may observe periodic outbreaks of the pest. In effect, intolerant regulating processes create thresholds separating distinct dynamic behaviors, usually referred to as endemic and epidemic behaviors. If threshold functions can be defined in terms of measurable system variables, they offer a powerful approach for evaluating the risk of epidemics in managed ecosystems. Methods for defining threshold functions and constructing risk decision models are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.544

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

A study of natural mortality in larvae of the cabbage looper,Trichoplusia ni(Hübner), feeding on experimental broccoli plantings in Riverside, Calif., revealed that ca. 10% of the larvae collected from July through October 1979 had a disease caused by a rickettsia-like organism. The disease occurred most commonly in 2nd- and 3rd- instars, where the rates of incidence were 12.8 and 15.2%, respectively. All larvae that developed patent infections died from the disease.The disease was most easily recognized in larvae which were reared individually in the laboratory on artificial diet. Disease signs included an opaque yellow-white discoloration on the body, incomplete shedding of the molted cuticle, reduced feeding activity, and a retarded growth rate with concomitantly increased larval longevity.At the histological level, the hemolymph of diseased larvae was milky white and contained numerous refractile vesicles that were diagnostic for the disease. Electron microscopy demonstrated slightly curved bacilliform particles, 160 by 420 nm, developing within these vesicles. Vesicles and particles also were found in the cytoplasm of epidermal, tracheal matrix, and fat body cells. The disease was transmitted to healthyT. nilarvae by injecting them with diluted hemolymph from diseased larvae. About 50% of the treated larvae developed typical signs of disease and subsequently died.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.550

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

Life tables (1977–1980) are presented for three generations of the white pine weevil,Pissodes strobi(Peck) (Coleoptera: Curculionidae), a pest insect of eastern white pine,Pinus strobusL. Typically, female weevils oviposited ca. 140 eggs per terminal leader of a host tree in the spring; however, only 1 progeny adult survived to the following spring. Average generation survival (SG = 0.008) and total generation mortality (K = 2.08) reflected observed small increases in weevil infestation each year. Key factor analysis suggested that larval, pupal, and winter submortalities were the major influences on population change. Submortality factors were: (1) egg infertility, (2) pitch-drowning, (3) larval instraspecific competition, (4) natural enemy predation and parasitism, (5) nonemergent brood adults, (6) unknown cause(s) of death, and (7) effect of climatic conditions on overwintering adults.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.555

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

Three collection methods were compared as measures of pest and beneficial arthropod numbers in cotton: a visual examination of plants, a modified berlese-funnel method, and whole-plant collection in cloth bags. Numbers of arthropods collected by the three methods were compared, with developmental stages separated where possible. No significant differences in the numbers collected by the three methods were detected when arthropod populations were at low densities. No single method was most effective for estimating all life stages of two or more particular arthropod species. A combination of the bag and berlese-funnel methods provided a better estimate for some arthropod populations than the use of bags alone. Some of these methods are suitable for research purposes, but none are feasible for use by commercial pest control advisors.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.565

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

This paper presents a method for clarifying the relationships between development rate curves and temperature regimes in affecting development accumulation or physiological time. By this method, one can determine the conditions under which changes in the parameters of the development rate curve will be most significant to the ecology and evolution of insect life histories. In the examples considered, the most important parameters of the development rate curve were its height, Rm, and its position, Tm. Its spread, Tσ, played a lesser role. The response of development accumulation to changes in these parameters was monotonic, except in the case of variation in position during midsummer for high values of mean annual temperature, in which case increasing Tmmay either increase or decrease development accumulation.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.573

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

Populations of five insect species—Lygus hesperus(Knight); the western flower thrips,Frankliniella occidentalis(Pergande); the pea aphid,Acyrthosiphon pisum(Harris); a damsel bug,Nabis americoferus(Carayon); and the minute pirate bug,Orius tristicolor(White)— increased slightly in bean fields after cutting of alfalfa hay. More definite increases of insects in bean fields occurred after hay cutting in 1978, when all hay study fields were cut on the same day, as opposed to 1979 and 1980, when adjacent hay fields were cut over a 10-day period. Proximity to a hay field did not correlate with large insect buildup in bean fields. No significant differences were recorded in numbers of these insects 10, 50, and 100 m into bean fields when adjacent hay fields were cut. Lygus bugs and thrips did not appear in beans in large numbers, and invaded beans only late in the growing season.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.578

出版商:Oxford University Press    

年代:1982

数据来源: OUP

摘要:

This paper discusses the various functions that have been used to predict the duration of insect life stages and presents a new algorithm for this purpose based on a polynomial function. The model was derived primarily for predicting biological events in the life history of the alfalfa weevil,Hypera postica(Gyll.), but gave equally precise simulations for three other species. Designed for a hand calculator, it is amenable to real-time weather acquisition and offers a practical alternative to the Stinner algorithm and other non-polynomial models for monitoring the development of insect pest populations.

ISSN:1754-5692    

DOI:10.1093/ee/11.3.581

出版商:Oxford University Press    

年代:1982

数据来源: OUP