摘要:

Behaviors ofEretmocerussp. nr.californicusHoward females onBemisia argentifoliiBellows&Perring infesting sweet potato,Ipomoea batatas(L.) Lam, were described and quantified. Walking speeds of up to 1.3 mm/s were calculated for females searching for host whitefly nymphs on sweet potato leaves. Females encountered all host stages during searching with approximately the same relative frequency as their relative abundance (average of 17.03% of hosts available were encountered). Females also arrested and antennated all of the host stages with the same relative frequency as their encounter rate (62.8%). Females showed a clear and significant preference for probing second instars over all other stages. Of the hosts probed, females chose all stages for oviposition with the same relative frequency. Successful exsertion of the ovipositor under a host nymph occurred after initial probes 12 times and after repeated probing attempts 15 times. Oviposition occurred under 13.5% of the hosts assessed by antennation; however, 20 of the 27 (74%) nymphs under which the ovipositor was exserted received an egg. Females spent 41% of the total time in searching, host assessment, probing, and oviposition; the remainder of the time (59%) was spent host feeding, grooming, and resting.

DOI:10.1093/ee/24.2.412

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Scab–resistant cultivars can reduce the need for fungicides in apple production. However, management of powdery mildew,Pudosphaera leucotricha(Ell.&Ell) Salmon, cedar apple rust,Gymnosporangium juniperi–virginianaeSchwein., and frog–eye leaf spot,Botryosphacria abtusa(Schwien.), may require limited fungicide use. Because fungicides can have mite–suppressive activity, it is important to determine the impact this reduction would have on mite populations. This study, conducted during 1988 and 1989, investigated the impact of a fungicide spray program (six applications of benomy1 and mancozeb versus no fungicide application) on phytophagous and predacious mite populations in a Vermont apple orchard. Levels of mite infestation were determined on four scab–resistant cultivars by counting motile phytophagous and predacious mites on leaf samples collected on 16 dates in each growing season. Data were evaluated separately for each cultivar, on each assessment date and over time, using an analysis of variance with a completely randomized design. Within each cultivar there were three to five single tree replicates per treatment. The impact of the fungicide spray program on predacious mite populations was clearly evident in both years. Approximately 4 wk after the last fungicide application, significantly higher predacious mite populations were detected on nontreated trees. In, 36 (97.3%) of the 37 samples for all cultivars in which there was a significant difference in predacious mites, the mean number of predacious mites was significantly higher on nonfungicide treated trees. In 1988, few significant differences in phytophagolls mite populations within cultivars were detected. However, incidences where there were significant differences in phytophagolls mite, populations increased in 1989; in the majority of the incidences, populations were significantly higher on fungicide–treated trees. This study shows that a fungicide spray program consisting of six applications can affect the mite populations on apple trees. This study also documents the potential benefit of eliminating fungicide applications.

DOI:10.1093/ee/24.2.423

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Foliar sprays ofSteinernema carpocapsae(Weiser) All strain (10,000 infective juveniles per milliliter) on chrysanthemums (‘Manatee Iceberg’) effectively controlled second instars of a serpentine leafminer,Liriomyza trifolii(Burgess) (>85% mortality), in laboratory tests, under conditions of high humidity in plastic cages. Increasing the duration of caging chrysanthemums gave consistently higher mortality of leafminer. Free moisture on the leaf surface and increased humidity enhanced the survival and activity of entomopathogenic nematodes. Glycerine was the most effective adjuvant tested for increasing the mortality of leafminer by nematodes. Wilt Pruf, Folicote, and Sunspray Ultrafine Spray oil were ineffective adjuvants. A research greenhouse test using two consecutive applications ofS. carpocapsae(3 and 4 d after oviposition by leafminer) gave>80% mortality of leafminer with or without glycerine. Abamectin gave significantly greater mortality (99.6%) than any nematode treatment.

DOI:10.1093/ee/24.2.431

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A biological control program for European corn borer,Ostrinia nubilalis(Hübner), usingTriclogramma nubilalisErtle&Davis andBacillus thuringiensisvar.kurstakiwas tested in plots of sweet corn 1990 and 1991.Trichogrammawere released during the egg mass recruitment period ofO. nubilalisto bracket the peak egg mass deposition period. One or twoB. thuringiensisapplications were targeted against host larvae that escapedT.nuilaleparasitism in the egg stage. The European corn borer phenology model adequately predicted the timing and shape of the adult Right and egg recruitment periods in 1990 and 1991. The releasedTrichogrmmaparasitized 70 and 56% of the European corn borer eggs in 1990 and 1991, respectively. In both years,<20% of the host eggs hatched in theTrichogrammarelease plots, compared with 38–,56% in the control plots. Total mortality of European corn borer from egg deposition to sweet corn harvest was 94 and 92% in 1990 and 1991, respectively. The stage structure of the European corn borer population at sweet corn harvest in 1991 did not differ between theTrichogrammarelease and no release plots. The proportion of sweet corn ears free of European corn borer larvae valied with position of the plots relative to nearby sudangrass, and ranged between 0.7 and 0.9 in the release plots, compared with 0.6– 0.65 in control plots in 1990 and 1991, respectively.

DOI:10.1093/ee/24.2.436

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Biological control ofTetranychus urticaeKoch was studied on hops,Humulus lupulusL., a rapidly growing perennial crop, in westem Oregon. Single or mixed species ofNeoseiulus fallacis(Garman),Metaseiuius occidentalis(Nesbitt),Typhlodromus pyriScheuten, andAmblyseius andersoniChant were released inoculatively into individual plants in 1992–1993. Success ofT. urticaecontrol depended on the phytoseiid species released and the ratios and distributions of pest and predaceous mites. The most effective control was byN. fallacis or M. occidentalisor a mixture of both species. In 1993,M. occidentalisprovided poor control, probably because of cool weather.T. pyriandA. andersoniprovided some control, but always less thanN. fallacisandM. occidentalis. Analysis of spatial distributions indicated that bothN. fallacisandM. occidentalisdispersed throughout hop plants ifT. urticaewere not abundant, but they stayed on the lower parts of the plant whenT. urticaewere abundant. Factors governing the distributions and dispersal ofT. urticaeand phytoseiids on hops and the effectiveness of biological control are discussed.

DOI:10.1093/ee/24.2.446

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A laboratory experiment was conducted to determine whether leaf exudates could be used as a source of adult nutrition for the squash bug,Auasa tristis(De Geer), egg parasitoid,Gryon pennsylvanicum(Ashmead), and to compare adult and progeny fitness traits when female Wasps were provided with squash leaves, a standard honey diet, a combination of leaves and honey, or water only Results showed that fecundity, progeny developmental rates, and progeny survival did not differ significantly when females were exposed to different dietary sources. Adult longevity was shorter on squash leaves without honey than on leaves with honey or the honey–only diet. However, reproductive fitness was not reduced because oviposition had been completed before death of the adult females. When only water was provided, parasitoid females lived only a few days. Observations showed that squash leaves have two kinds of trichomes (hair–like and peg–like), both of which produce droplets that are fed on by both sexes ofG. pennsylvanicum.Nutrient analyses revealed that exudates from the hair–like trichomes are composed predominantly of monosaccharides (mainly glucose and galactose), and that the peg–like trichomes produce glucose and some protein. Thus, these trichomes appear to serve as extrafloral nectaries and may provide an important energy source for augmentatively releasedG. pennsylvanicum.

DOI:10.1093/ee/24.2.454

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The ash whitefly,Siphoninus phillyreae(Haliday), was introduced into northern California in 1989–1990. It developed through two or more generations from fall through spring (overwinter) on toyon,Heteromeles arbutifoliaRoemer, a native broadleaf evergreen shrub. In spring, whiteflies migrated to ash,Fraxinus velutinaTorrey, and other deciduous hosts; whiteflies were absent or not detected on toyon during each of the three summers from 1990 to 1992. Ash whitefly densities were increasing before natural enemy introductions. About 98% of ash leaves were infested in 1991 (before establishment of introduced natural enemies) in comparison with<1% of leaves infested in 1992 (after natural enemy establishment).Whitefly densities declined by two to four orders of magnitude on both ash and toyon after the introduction and establishment ofEncarsia inaron(Walker) (=partellopea) andClitostethus arcuatus(Rossi) (Coleoptera: Coccinellidae).E. inaronis apparently the more important species. Unlike ash whitefly, which must migrate from deciduous hosts to overwinter on evergreen plants,E. inaroncan survive the deciduous host–free period as adults or by slowly developing as immatures on fallen ash leaves, as well as by parasitizing whiteflies on evergreen plants. Biological control may be enhanced because overwintering parasiloids can already be present in the deciduous–host (ash) habitat when whiteflies migrate from toyon back to ash during the spring.

DOI:10.1093/ee/24.2.459

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

This is the first area–wide multiyear survey for prevalence rates ofNezygites fresenii(Nowakowski) Batko, an important natural enemy of the cotton aphid,Aphis gossypiiGlover. In both 1992 and 1993,N. freseniioccurred throughout a wide geographical area in Arkansas and along the Mississippi River flood plain and showed a significant trend for a decrease in prevalence rates from south to north in both years. In 1992,N. freseniiwas present inA. gossypiipopulations in 87.5% (n = 24) of aphid–infested commercial cotton fields. Prevalence rates in 1992 (sampled on 2.3 and 29 July) ranged from 0 to 100% with a mean prevalance rate of 50.1 %. In 1993 (sampled on 7 and 8 July),N. freseniiwas present in 77.8% (n = 18) of aphid–infested Commercial cotton fields and prevalence rates ranged from 0 to 57% with a mean of 13.7%. Prevalence ofN. freseniiwas periodically determined to study the development of epizootics in 1991 (one research field), 1992 (three commercial cotton fields and one research field), and 1993 (four commercial cotton fields and one research field) in Arkansas. Epizootics occurred in all 10 fields and generally causedA. gossypiipopulations to decline rapidly.N. freseniiinfected alatae were observed =2 wk earlier than the first infected apterae. Migrating infected alatae may be a mechanism by whichN. freseniiis spread within and between fields and may also serve as an early indication of impending epizootics. Infected apterae may also be useful indicators of imminent epizootics becauseA. gossypiipopulations generally declined 1–3 wks afterN. freseniiwas first detected in apterae.

DOI:10.1093/ee/24.2.465

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We studied the growth and development of the parasitic phorid flyPseudacteon litoralisBorgmeier in the fire ant,Solenopsis invictaBuren. The fly apparently lays one egg in or on the thorax of a major worker. The newly hatched maggot migrates into the head of the ant where it develops through its last two instars in =3 wk (23°C). Just before pupariation, an enzyme is apparently released that begins dissolving the cuticular membranes of the ant. The maggot then consumes the entire contents of the ant head, a process that usually results in decapitation of its living host. After pushing the mouth parts aside, the maggot pupariates within the empty head capsule, positioned so that the anterior three segments precisely fill the oral cavity. The pupal stage lasts =3 wk. Results of this study indicate that it should be possible to rear this fly for release as a natural biological control agent of imported fire ants in the United States.

DOI:10.1093/ee/24.2.475

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Tryptophan, of five aromatic/heterocyclic amino acids (tyrosine, phenylalanine proline, histidine) provided significant protection of theHeliothisbaculovirus (HzSNPV) from inactivation by simulated sunlight ultraviolet (SUV). Fifty percent of SUV protection of HZSNPV with tryptophan or tyrosine was obtained at 0.03 mg/ml and 0.5 mg/ml, respectively. Rates as high as 100.0 mg/ml of phenylalanine, histidine, or proline provided<.50% protection. The extent of tryptophan protection was correlated with its absorption in the sunlight UV-B spectra.

DOI:10.1093/ee/24.2.480

出版商:Oxford University Press    

年代:1995

数据来源: OUP