摘要:

Rhopalamyia califarnicaFelt is an endemic cecidomyiid midge which develops within terminal galls onBaccharis pilularisDC in California. Individual galls normally contain more than one larva and can thus be viewed as discrete host patches in space and time. At the Jasper Ridge Biological Preserve, the number of midge larvae per gall varied from 1 to 40 and individual galls were exploited by as many as five species of parasites. Total percentage of parasitization per gall was relatively constant, regardless of the number of host larvae per gall. Instead of being density-dependent, total mortality was species dependent–the proportion of hosts parasitized per gall was directly related to the number of species of parasites reared from the gall. However, the total proportion of hosts parasitized in the samples was relatively low (37.5%) because most galls contained either zero or one species of parasite. Less than 1% contained five species and less than 5% contained four species. The evidence is consistent with the hypothesis that this guild is structured so as to reduce the incidence of interspecific competition among the parasites, and it raises the possibility that the structure of a parasite guild may not necessarily be compatible with the goals of biological control. I suggested that parasite guilds such as this one might be “restructured” so as to actually increase their efficiency in maintaining pest populations at relatively low levels. Additional aspects of restructuring parasite guilds are discussed.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.1

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

The population dynamics of the green peach aphid (GPA),Myzus persicae(Sulzer), were examined on four commercial potato cultivars,Solanum tuberosum tuberosum(L.) cv. Katahdin, Norchip, Superior, and 8NW-8, with differing maturation rates and on one wild potato,S. canasensePI 283074. GPA abundance, population growth rate, alate abundance, and within-plant distribution were compared among cultivars. Results showed that GPA numbers were similar among commercial cultivars during most of the growing season. However, GPA population dynamics were influenced by potato plant phenology. GPA were more abundant earlier, populations peaked sooner, and declined earlier on the short-season cultivar, ‘Superior’. Populations on longer-season cultivars reached highest levels later. At 1,167 degree-days, GPA numbers were ca. 50% smaller on ‘Superior’ than on the mid-season cultivar, ‘Norchip’. Fewer GPA were observed onS. canasensethan on the commercial cultivars. GPA populations reached one-half their highest level from 6 to 8 days sooner in the growing season on ‘Superior’ than on later-maturing cultivars. Alate numbers were greatest on ‘Superior’, followed by ‘Norchip’, ‘Katahdin’, and 8NW-8. GPA were found predominantly on the lower leaves of each cultivar. GPA population growth rates were greatest on the lower leaves and slowest on the upper leaves of each cultivar. GPA populations increased more rapidly on the upper, middle, and lower leaves of ‘Superior’ than on longer-season cultivars.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.7

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Laboratory-reared male redbanded leafroller moths,Argyotaenia velutinana(Walker), were marked and released into small field plots permeated with a pheromone component (Z)-11-tetradecenyl acetate at a release rate of 5 mg/h/ha. Pheromone-mediated activation occurred normally in released males whether or not they were previously exposed to disruptant before their normal peak of activity. Preflight behaviors such as wing-fanning while walking were followed by flight, but orientation to sex pheromone-baited traps in the plot center was significantly reduced compared to a control plot.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.12

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Developmental thresholds and thermal-unit requirements for egg hatching, larval and pupal development, and the period before oviposition were determined for the obliquebanded leafroller,Choristoneura rosaceana(Harris). An average of 111.9 degreedays (thermal units) above 10.0°C was required from oviposition to hatching. Development of the total larval stage required 435.6 degree-days. The developmental thresholds for different larval instars were variable, and significantly different from each other. The fourth larval instar had the lowest developmental threshold, 7.1°C. Other thresholds were: first instar, 11.0°C; second and third instars, 9.9°C; fifth instar, 8.8°C; and sixth instar, 11.4°C. Diapausing third-instar threshold was 11.1°C. Pupae required 117.4 thermal units (above 9.5°C) for adult eclosion. Females required a period before oviposition of 35.2 degree-days above 11.9°C. Egg, larva, pupa, and preoviposition period represented, respectively, 16, 62, 17, and 5% of the total thermal development period from egg to egg.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.17

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Robber flies were manually removed from 0.28- or 0.55-ha circular field plots four or five times a week for 6 weeks in order to reduce predation upon dipterous parasites of grasshoppers. Three species that prey upon Diptera,Efferia bicaudata(Hine),E. staminea(Williston), andMallophorina guildiana(Williston), constituted 94% of the robber fly population. Although removal plots always become partially (mean, 61%)repopulated through recruitment or immigration, the incidence of parasitism among grasshoppers significantly increased from an average of 2 to 3% in untreated plots to 5.5 to 6.5% in removal plots. During one season, the enhancement of parasitism was associated with a significant 12-day reduction in average longevity of grasshoppers (i.e., from 40 days to only 28 days). During a second season, however, average grasshopper longevity in all plots was only 15 days, and the potential effects of increased parasitism were not realized.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.20

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Euseius hibisci(Chant) (Phytoseiidae) preyed onBemisia tabaci(Gennadius) (Aleyrodidae) on cotton in the laboratory and developed to the adult stage feeding on a mixture of eggs and first and second instars ofB. tabaciwith 75% survival. Adult longevity and fecundity were greater when fed eggs than when fed first or second instars ofB. tabaci. An average of 4.5B. tabacieggs were consumed per adult female per day with a range of 0 to 18.4 eggs, but older whitefly eggs were less acceptable. Unfed mites in the controls did not oviposit. Longevity, fecundity, and the oviposition period ofE. hibiscifeeding onB. tabaciwere lower than those of pollen-fed mites.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.24

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Three low-level releases ofTrichogramma pretiosum(Riley), two at 12,500 and one at 37,500 per ha, at 7-day intervals, did not increase early seasonHeliothisspp. egg parasitism over that in untreated fields at Natchitoches, La., in 1978. Peak parasitism levels were 59.3 and 40.6% in control and release fields, respectively, but declined before peak egg deposition. Peak natural levels ofTrichogrammaspp. parasitism in the firstHeliothisspp. egg generation in cotton in 1979 at Bossier City and St. Joseph, La., were 89 and 62%, respectively.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.28

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

The gregarious encyrtid parasitoid,Anagyrus indicus, oviposits in all three nymphal stages and in the adult female stage of the spherical mealybug,Nipaecoccus vastator. In no-choice tests, the frequency of hosts parasitized, and the number of eggs deposited per host were significantly greater in third nymphal and adult female mealybugs than in either first- or second-stage nymphs. In choice tests, significantly more adult females were parasitized than third-stage nymphs, and the first and second nymphal stages were not parasitized.A. indicuswas able to complete development and emerge following parasitism of each of the four host stages, but parasitoid development was the fastest, the number of parasitoids emerging was the greatest, and the ratio of female to male parasitoids was the highest following oviposition in third nymphal and adult female hosts. Our findings have implications for mass-rearing and field colonization ofA. indicusand provide support for recent predictive models of reproductive strategies in parasitic Hymenoptera.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.32

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Rates of development of the egg, larval, prepupal, and pupal stages of the African buffalo fly,Haematobia thirouxi potans(Bezzi), were measured in the laboratory at 15, 18, 20, 25, and 30°C. Within this temperature range the relationship between rate of development and temperature was linear for each stage. Development rates of the immature stages ofH. thirouxi potanswere compared with those reported for bothH. irritans exiguade Meijere andH. irritans irritans(L.). Only the development rate of the larva ofH. irritans irritansdiffered significantly from that ofH. thirouxi potans.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.38

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

FemaleEucosma womonanaKearfott had a preoviposition period of 4.4 ± 0.5 days, after which they laid an average of 236.8 ± 18.1 eggs in the laboratory at 27 ± 2°C. Incubation averaged 6.3 ± 1.5 days. Larvae passed through five stadia in ca. 85.8 ± 6.8 (females) or 86.5 ± 6.9 days (males). The total life cycle for laboratory-reared specimens averaged 106.7 ± 4.7 days. Infestation of roots of sunflowers,Helianthus annuusL., byE. womonanalarvae on the High Plains of Texas was significantly reduced in plantings made after late April in 1982 and mid-May in 1983.

ISSN:0046-225X    

DOI:10.1093/ee/14.1.42

出版商:Oxford University Press    

年代:1985

数据来源: OUP