摘要:

The potential for biological control of the hop aphid using an aphid-derived isolate ofBeauveria bassianawas investigated in the laboratory and field. In initial bioassays using conidial suspensions at dosages ranging from 104to 108a conidia/ml, the isolate exhibited a high level of virulence toPhorodon humuli(Schrank), yielding a LC50of 1.37 × 105conidia/ml. LT50values decreased with increasing conidial dose, being 11.1 ± 4.2, 8.4 ± 4.0, 5.0 ± 1.5, 3.6 ± 1.5, and 3.1 ± 1.1 d at 104, 105, 106, 107, and 108conidia/ml, respectively. A potential for long-term control was demonstrated when conidial suspensions were applied to aphid-infested potted hop plants. Aphids increased only slightly during a 4-wk period on potted hop plants treated with a suspension of 107 conidia/ml. This was significantly lower than the net increase found on the controls and on plants treated with a suspension of 105conidia/ml. However, there was no mycosis detected in aphids when a 107 conidia/ml suspension was applied in an aphid-infested commercial hop yard.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.690

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The functional response for various stages of the predatory mite,Amblyseius cucumeris(Oudemans), on first instars of western flower thrips,Frankliniella occidentalis(Pergande), was determined. The predation trials were conducted on greenhouse cucumber and sweet-pepper leaf disks over a 24-h period at 26 ± 1°C and 12:12 (L:D) photoperiod. Prey densities ranged from 1 to 40 larvae per leaf disk. The mated female adults ofA. cucumeriswere the most effective predatory stage, whereas all male stages were ineffective predators. Use of this information on the predator-prey relationship betweenA. cucumerisandF. occidentalisfor improving and predicting the outcome of biological control ofF. occidentalison greenhouse crops is discussed.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.694

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The G13 strain ofSteinernema carpocapsae(Weiser), previously selected for enhanced host-finding of waxmoth larvae,Galleria mellonellaL., was subjected to selection for the same trait against scarab larvae. Twenty rounds of selection produced a 3.7-fold increase, from 18.4 to 68.7%, in nematode (S20 strain) location of nondiapausing larvae of the Japanese beetle,Popillia japonicaNewman. However, the overall improvement over wild-types (Foundation and All strains), after 33 rounds (13 againstG. mellonellaand 20 against scarabs) was 153- and 72-fold, respectively. Infective juveniles had difficulty locating diapausingP. japonicalarvae, and selection did not result in any enhancement in finding these larvae. Selection for host-finding of scarabs resulted in a 24.6% gain in host-finding ofG. mellonella, suggesting selection was for a general feature present at different levels in different hosts. The use of KOH to absorb CO2resulted in the complete inhibition of S20 strain response to insect hosts, verifying that nematodes have been selected for enhanced sensitivity to CO2. S20 nematodes were significantly less storage stable than the Foundation strain.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.700

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Laboratory experiments were conducted to assess the reproductive success ofSteinernema carpocapsae(Weiser) orHeterorhabditis bacteriophoraPoinar in soilborneSpodoptera exigua(Hübner) previously exposed toBeauveria bassiana(Bals.) Vuill. Treatments ofH. bacteriophoraplusB. bassianaresulted in higher total mortality ofS. exiguain soil than treatments with either nematode alone or fungus alone. ForS. carpocapsaeplusB. bassiana, insect mortality was not significantly different compared withS. carpocapsaealone. In treatments with nematode plus fungus, percentage mortality ofS. exiguafromS. carpocapsaeandH. bacteriophorawas reduced relative to the treatments with nematodes alone. These results suggest that inundative release of entomopathogenic nematodes whereB. bassianaoccurs may result in greater control of soilborne insect pests than application of nematodes alone.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.707

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Biological control of the sweetpotato whitefly,Bemisia tabaci(Gennadius), was undertaken using augmentative releases of the commercially available parasitoid,Encarsia formosaGahan, on commercial poinsettia (Euphorbia pulcherrimaWild.) stock plant production. Weekly releases of three to five parasitoids per plant were begun soon after the crop was planted (14 April) and continued until the end of poinsettia cutting production (1 September). The effect ofE. formosaon the development ofB. tabaciwas significant on 14 and 16 of 21 weekly sampling dates for adults and immatures, respectively (unpairedttest,P= 0.05). In control cages, there were approximately a 10- and 100-fold greater number of adult and immature whitefly populations recorded, respectively, compared with the biological control area. Applications of insecticidal soap were required four times over the 5-mo duration of the trial when the level of whiteflies caught on yellow traps exceeded an a priori threshold level of 10–15 whiteflies per trap. Although a dramatic decrease in the whitefly population was observed in the biological control area, this was not sufficient to prevent whitefly egg deposition on terminal growth, which is the harvestable product. A combination of parasitoid releases, applications of insecticidal soap, and roguing obviously infested cuttings were required to produce export-quality cuttings. The strategy of using biological control in ornamental crop production is discussed in light of these results.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.713

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Weeds adjacent to commercial tomato production fields on the west coast of Florida were surveyed during 1982–1983 to determine which species serve as reservoirs of Agromyzidae leaf miners and their parasitoids. About 95% of the leafminer larvae were observed in foliage of seven weed genera (Solanum americanumMill.,Erechtites hieracifolia(L.),Bidens alba(L.),Gnaphaliumspp.,Physalisspp.,Sonchusspp., andRumex obtusifoliusL.) and volunteer tomato even though these species accounted for only about 13–42% of the weed canopy.Liriomyza trifolii(Burgess) andL. sativaeBlanchard accounted for 45 and 40%, respectively, of the leafminer adults reared from infested foliage and were most prevalent fromS. americanumandB. alba. The larval–pupal parasitoidsOptus dissitusMuesebeck,Oenonogastra microrhopalae(Ashmead), andHalticoptera circulus(Walker) were the most abundant leafminer parasitoid adults reared from leafminer infested foliage, accounting for 37.8, 15.1, and 15.8%, respectively, of the total reared. The larval parasitoidsNeochrysocharis punctiventris(Crawford),Diglyphus begini(Ashmead), andD. intermedius(Girault) accounted for 8, 5, and 2.5%, respectively.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.720

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

More than 15 species of capitulum-feeding insects colonized a randomized garden plot of yellow starthistle, globe artichoke, cultivated safflower, andCirsium creticum(Lam.) D'Urv. in northern Greece in 1985. Among these insects were seven potential biocontrol agents of yellow starthistle: the cynipid wasp,Isocolussp.; the tephritid flies,Chaetorellia australisHering,Terellia uncinataWhite, andUrophora sirunaseva(Hering); and the curculionid beetles,Bangasternus orientalis(Capiomont),Eustenopus villosus(Boheman), andLarinus curtus(Hochhuth). These potential agents only attacked yellow starthistle plants, which were grown from seed collected in Greece and the United States. This host specificity data was used to justify the subsequent release ofC. australisandE. villosusin the United States. The relative intensity of interspecific interactions among capitulum-feeding insects of yellow starthistle is discussed, as well as the potential effectiveness ofE. villosusas a biocontrol agent. This study points to the usefulness of the open field test in host specificity determination of insects for biological control of weeds.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.724

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

A pathogenic fungus (Neozygitessp.) caused dramatic reductions in spider mite populations in artificially infested soybean plots in both 1987 and 1988. Buildup of the pathogen occurred for approximately two weeks, with the most devastating epizootic infecting 100% of living mites sampled and reducing mite intensity up to 95% over a six-day period. Fungal activity was very dependent upon environmental conditions, with spread of the disease occurring only during sustained cool and humid weather. Thick-walled resting (overwintering) spores were found in 7.8% of all mites sampled late in 1988. This is the first study in the Midwest to show thatNeozygitessp. can overwinter away from its host. The impact of fungal epizootics on spider mite management is also discussed.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.731

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The reproductive conditions of female corn earworm,Heliothis zea(Boddie), moths caught in blacklight (BL) traps and those captured in sweep nets in corn during 1988 and 1989 were compared. There was no significant difference in mean number of spermatophores per female between moths captured in sweep nets and those caught in BL traps. Number of spermatophores averaged 2.2 per female. The pattern in the number of spermatophores per female over time in corn earworm moths caught in BL traps closely approximated that of females captured in sweep nets. The pattern of change in sex ratio in corn earworm moth catches in BL traps closely approximated that of moths captured in sweep nets, with some exceptions. Profiles describing relative number of chorionated eggs and amount of fat were similar in moths collected by sweep nets and those caught in BL traps. Data indicate that catches in BL traps may be used as an alternative to nocturnal sampling of adults with sweep nets for describing the reproductive condition of female corn earworm moths in corn.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.736

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Adult clouded plant bugs,Neurocolpus nubilus(Say), were caged for 2 d on individual cotton plants (Gossypium hirsutumL.) during two stages of plant physiological development. Regression analyses of number of plant fruiting structures and yield on insect densities indicated that feeding byN. nubilusat the peak squaring period caused shedding of small pinhead squares and delayed crop maturation, although with no significant effects on total yield. The effects ofN. nubilusfeeding were less apparent at boll maturation. Observations of cotton fields with a history ofN. nubilusinfestations and analysis of data collected by the Mississippi Cooperative Extension Service in northern Mississippi indicated thatN. nubilusoverwinters in the egg stage, develops its population on several host plants, and moves to cotton during late season, when cotton is less susceptible to its damage.

ISSN:0046-225X    

DOI:10.1093/ee/20.2.742

出版商:Oxford University Press    

年代:1991

数据来源: OUP