摘要:

The feeding niches of 10 spider species that are polyphagous insectivores were compared by computing coefficients of niche breadth and niche overlap. The study is based on predation evidence from an insecticide-free cotton plantation in east Texas. All overlap values were<1.00 (range, 0.08–0.94), which indicates that each spider species has its own feeding niche in the cotton agroecosystem. Diet breadth, that is inversely related to feeding specialization, was computed for each species. The highest value was approximately five times higher than the minimum, which indicates considerable differences between species in feeding specialization. Diet breadth values indicate that large web weavers exhibited a less specialized feeding behavior (relatively broad feeding niche) compared with small web weavers (narrow feeding niche). Prey specialists in this study concentrated on either aphids or fire ants as a primary food source. The nonweb-building spiderOxyopes salticusHentz, which actively searches the cotton plant for prey (up to=6 mm maximum length), showed the highest diet breadth value (broad feeding niche) under the conditions of this experiment. This abundant species, which is considered a highly beneficial biocontrol agent of smaller cotton pests, shows high flexibility in its foraging patterns.

DOI:10.1093/ee/23.5.1294

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Temperature-dependent development of a Czechoslovakian population of the parasitoidAphidius matricariaeHaliday was measured at eight constant temperatures between 11 and 31°C using the Russian wheat aphid,Diuraphis noxia(Mordvilko), as a host. Development rate from oviposition to emergence of adult wasps increased linearly with increasing temperature between 11 and 26°C. No adult wasps emerged from parasitized aphids at 31°C. Requirements for development from oviposition to adult eclosionwere 273.1 ± 5.9 degree-days above a threshold of 4.5 ± 0.4°C. These results are compared with previously reported data on temperature-dependent development of other populations ofA. matricariaeand the host,D. noxia.

DOI:10.1093/ee/23.5.1304

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The nuclear polyhedrosis virus ofAnticarsia gemmatalis(Hübner) was released into soybean fields at two sites in Louisiana. The spread of the virus outside release plots was monitored by samplingA. gemmatalislarvae, predatory arthropods and parasitoids ofA. gemmatalis, and soil. According toA. gemmatalissampling, the virus spread at a rate of 0.8 and 1.2 m/d at the Crowley and Baton Rouge sites, respectively, within ≍6 wk after it was released. The virus spread distances of up to 44 and 58 m at Crowley and Baton Rouge, respectively, during that season. The rate of spread detected inA. gemmataliswas significantly (P>0.01) correlated with the rate detected by sampling and bioassay of predatory arthropods and parasitoids, primarily the former. There also was circumstantial evidence implicating birds and farm machinery in viral transport; 80% (n= 15) of bird droppings sampled at the Baton Rouge site during viral spread contained viableA. gemmatalisnuclear polyhedrosis virus. The rate of spread did not differ by direction from release plots. The prevalence of viral disease decreased at increasing distances from release plots for 3 yr after release at the Crowley site and during the 1st yr at Baton Rouge. The amount of virus in soil after the first season at the Crowley site decreased from 3,598 polyhedral inclusion bodies per gram in the release plots to 131 and<1 polyhedral inclusion bodies per gram at distances of 46 and 114 m, respectively, but this decrease was not significant.

DOI:10.1093/ee/23.5.1308

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Long-established populations ofTyphlodromus pyriScheuten were less common in plots in 1993 with denseZetzellia mali(Ewing) than in plots with sparseZ. mali. Also, newly releasedT. pyrihad more difficulty colonizing plots withZ. malithan without, but less difficulty thanMetaseiulus occidentalis(Nesbitt) had had in 1992. Newly releasedZ. malidid not establish well in a plot that hadT. pyrionly, butZ. maliseemed to be displacingT. pyriafter 4 yr in some mixed-species release plots ofM. occidentalisandT. pyri. After immigration from nearby vegetation to apple, colonization byAmblyseius andersoni(Chant) was less in azinphosmethyl-treated plots than in similar untreated plots. Colonization byA. andersoniwas greatest in plots with fewT. pyrior Z.malior both but some occurred in all plots not sprayed in 1993 (those originally receiving no releases, single or mixed-species releases ofT. pyri, andM. occidentalisin 1990). Colonization byA. andersoniwas greatest whereM. occidentalishad been displaced in 1991 or 1992 byZ. mali.Results are discussed in relation to long-term biological control and more biologically based integrated pest management.

DOI:10.1093/ee/23.5.1317

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Green peach aphid,Myzus persicae(Selzer), populations were monitored and examined for pathogens at Moscow and Troy, ID, in 1991 and near Yakima, WA, in 1991–1992.M. persicaeinfesting a peach orchard, broadleaf weeds within and around the periphery of the orchard, and nearby potato fields near Yakima were observed from March until November. Potatoes and nonsolanaceous plants in home gardens in Moscow and Troy also were monitored forM. persicaeand examined for pathogens during the growing season. In 1991, aphid numbers reached a maximum of 6,070 per 5–15-cm peach twig segments on 29 May but only nine per 15–0.15-m twig segments in 1992. Fungal pathogen activity was barely discemable on tree-borne aphids in the orchard but was observed more frequently from aphids infesting weeds beneath the trees. An epizootic of Entomophthorales occurred on aphids infesting solanaceous (potatoes) and nonsolanaceous hosts in home gardens in Moscow and Troy, (Latah County), Idaho, in 1991.Verticillium lecanii(Zimmerman) Viegas was identified fromM. persicaeon peach leaves;Beauveria bassiana(Bals.) Vuillemin andConidiobolussp. were identified from aphids on potatoes. Aphids collected from weeds growing in and near the peach orchard were infected withEntomophthora chromaphidisCornu,Conidiobolus coronatus(Constantin) Batko,C. obscurus(Petch) Hall&Dunn, andV. lecanii.Aphids on potatoes and nonsolanaceous hosts at Moscow and Troy were infected withPandora neoaphidis(Remaudiere&Hennebert) Humber,E. chromaphidis, andConidiobolusspp. Aphid populations were much lower in 1992 both within the orchard and in potatoes.

DOI:10.1093/ee/23.5.1326

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Single inoculative applications ofSteinernema scapterisciwere made on golf courses in north central (Alachua County) and southeastern (Broward County) Florida. Nematode-infectedScapteriscusspp. mole crickets were collected from eight of nine treated plots and from five of six treated plots in Alachua and Broward counties, respectively. However, infected individuals were collected with regularity from only two courses in Alachua County where level of infection was greatest during the spring (March-June). Weekly infection levels for weeks 1–12 after treatment ranged from 0–100%. Infection ofScapteriscusspp. adults from treated plots in Alachua County, 25.2%, was significantly greater than that for nymphs, 1.2%; and infection ofScapteriscus borellii, 25.0%, was significantly greater than that ofS. vicinus, 11.0%. Nematode-infected mole crickets were collected from four control plots in Alachua County and from one in Broward County during the 2nd yr after treatment. Significantly fewer mole crickets were collected in 24-h trap catches the 2nd yr after treatment on all treated plots combined and control plots combined in both counties. Mean trap catch was reduced 68, 62, and 41% the 2nd yr on treated plots where the nematode persisted; on control plots where infected crickets were collected; and on control plots where the nematode was not detected, respectively. Damage ratings and number of mole crickets soap-flushed from treated plots were significantly reduced the 2nd yr after treatment. Results indicateS. scapteriscican serve as an inoculative biological control agent forScapteriscusspp. mole crickets on golf courses and as a biopesticide for relatively rapid suppression of pest populations.

DOI:10.1093/ee/23.5.1331

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

This investigation compared the potential of adult carabids (ground beetles) as predators of fifth-instar codling moth,Cydia pomonella(L.). The three objectives of the research were the following: (1) to determine which species could killC. pomonella, (2) to compare the degree of carnivory and consumption pattern of selected species of carabids, and (3) to estimate carabid predation ofC. pomonellain the field. The results indicated that 75% or more ofPterostichus lustransLeConte,Pterostichus cursitorLeConte,Pterostichus (Hypherpes)spp.,Harpalus pensylvanicusDeGeer, orAnisodactylus californicusDejean individuals were capable of killingC. pomonellain the laboratory. The most effective predators were species ofPterostichus, even when an alternative plant food (rolled oats) was provided. An average of 60% of tetheredC. pomonellawere consumed each night by carabids in early June, but predation intensity declined June–July. The carabid species seen attacking tethered prey includedAgonum punctiformeSay,Calathus ruficollisDejean,H. pensylvanicus, andP. (Hypherpes)spp. Adults ofPterostichusspecies appear to be important early-season predators ofC. pomonellain orchards.

DOI:10.1093/ee/23.5.1338

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Releases ofEncarsia luteolaHoward andDelphastus pusillusLeConte were evaluated for their ability to controlBemisia argentifoliiBellows&Perring, n. sp. greenhouse-grown poinsettias. Three treatments, each replicated three times, were used to assess the impact of natural enemy releases onB. argentifoliipopulations: (1) a complete exclusion of natural enemies cage, (2) an identical exclusion cage receiving natural enemy releases as a control for cage effects, and (3) releases of natural enemies onto plants within the greenhouse but outside of either cage. Weekly releases of the parasitoidE. luteolawere initiated the week the plants entered the greenhouse and three releases ofD. pusillus, 1 wk apart, were made whenB. argentifoliipopulations rose dramatically 9 wk into the trial. Release rates for both natural enemies were one insect per plant per week. Weekly collected leaf samples were examined with the aid of a dissecting microscope. The numbers of live whiteflies were recorded by developmental stage as were the numbers of dead (resulting from natural causes,D. pusilluspredation, orE. luteolahost-feeding) and parasitized whitefly nymphs. The lack of a significant difference in whitefly densities between the two natural enemy release treatments suggested the absence of a cage effect on whitefly populations. Whitefly densities within the complete exclosure cages were significantly greater than the whitefly densities in either of the two natural enemy release treatments, indicating a significant impact of natural enemy releases onB. argentifoliiinfestations. Whitefly damage to harvested plants within the natural enemy release areas was not significantly different from the damage level observed in the grower-treated area. The direct cost associated withB. argentifoliibiological control (166.32 per greenhouse section) was ≍5 times greater than the insecticide-basedB. argentifoliimanagement program currently used by poinsettia growers. This cost differential can be reduced if the indirect environmental and worker-safety costs associated with insecticide use are included, and further reductions should accompany increased commercial availability ofD. pusillus.

DOI:10.1093/ee/23.5.1346

出版商:Oxford University Press    

年代:1994

数据来源: OUP

DOI:10.1093/ee/23.5.1354

出版商:Oxford University Press    

年代:1994

数据来源: OUP

DOI:10.1093/ee/23.5.1355

出版商:Oxford University Press    

年代:1994

数据来源: OUP