摘要:

The effect of entomopathogenic nematodes on nontarget arthropods in the laboratory, field soils, and a stream were assessed. In the laboratory, adult predators were less susceptible to the nematodesSteinernema carpocapsae(Weiser) (Rhabditida: Steinernematidae) andHeterorhabditis bacteriophoraPoinar (Rhabditida: Heterorhabditidae) than the immature stages. In field tests, entomopathogenic nematodes that had significantly suppressed pest populations (Popillia japonicaNewman, Japanese beetle,Scapteriscus vicinusScudder, tawny mole cricket,Otiorhynchus sulcatus(F.), black vine weevil,Delia radicum(L.), cabbage maggot, andDiabrotica virgifera virgiferaLeConte, western corn rootworm) did not adversely affect the numbers of nontarget soil arthropods in comparison with the untreated control. In contrast, broad-spectrum chemical insecticides (isofenphos, ethoprop, or chlorpyrifos used as chemical checks) significantly reduced or showed a tendency to reduce nontarget arthropod populations. In a stream trial,S. carpocapsaesignificantly reduced black fly larval populations, but the nontarget insects often increased in the treatment sites. Decreases in nontarget populations were matched by approximately equal or greater reductions in the upstream controls. We conclude that entomopathogenic nematodes do not adversely affect nontarget arthropods when used for short-term control of insect pests.

DOI:10.1093/ee/20.3.815

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The phytoseiid predatorsNeoseiulus fallacis(Garman) andMetaseiulus occidentalis(Nesbitt) were reared together and fed onTetranychus urticaeKoch to determine the possibility of coexistence and the effect of vapor pressure deficit on the two species. Additionally, developmental times for the two predators feeding on the spruce spider mite,Oligonychus ununguis(Jacobi), were determined at 14°C and vapor pressure deficits of 1, 4, 6, and 10 millibars (mb).N. fallacisandM. occidentalisrespond to vapor pressure deficit in essentially opposite ways. In the interaction treatments, populations ofN. fallacisreproduced rapidly at low vapor pressure deficits (high atmospheric moisture) but vapor pressure deficits of 10 mb or greater severely limited population growth of this species;M. occidentalispopulations grew more readily at higher vapor pressure deficits (>10 mb). At 14°C, egg mortality forM. occidentaliswas 25, 10, 20, and 45% at 1, 4, 6, and 10 mb, respectively; egg mortality forN. fallacisat these respective vapor pressure deficits was 25, 0, 15, and 80%. At 14°C, developmental periods for immature stages ofN. fallacisamong vapor pressure deficits were significantly different in the egg and larval stages and in the egg stage forM. occidentalis.N. fallacisis directly subject to the physical environment (vapor pressure deficit effect on egg mortality) whereasM. occidentalisis subject to differences in survival responses (less prolific thanN. fallacisat a given vapor pressure deficit and temperature). The differential response of the two predators suggests that releases of both species to controlO. ununguison Fraser fir in western North Carolina can be optimally timed based on humidity conditions.

DOI:10.1093/ee/20.3.823

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

A simulation model of the population dynamics ofScirpophaga incertulas(Walker) was developed for ultimate use in pest management programs. The processes of development, mortality, migration, and oviposition are modeled. Information from literature and field data were used to set the model's parameters. The model satisfactorily simulated the timing of egg, larval, and pupal population density peaks in farmers' fields for both the 1987 wet and 1988 dry seasons in the Philippines. Most population peak numbers lie within ±2 SD of the field means. Sensitivity analyses indicated that the most important factors in the system were egg, larval, and pupal developmental rate; egg mortality rate due to predation and parasitism; larval mortality rate related to plant age; immigration rate; and oviposition rate. Effects of growing resistant varieties, releasing egg parasites, and applying insecticides on larval populations in the 1987 wet season were evaluated with the model and discussed in regard to their implications for pest management.

DOI:10.1093/ee/20.3.832

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Mortality to the egg stage of Colorado potato beetle,Leptinotarsa decemlineata(Say), from endemic predators was assessed in unsprayed plots within commercial potato fields in western Massacusetts in 1986 and 1987. Direct measurement of recruitment into the egg stage and of losses to predation gave estimates of total stage-specific mortality for each generation of Colorado potato beetle and daily mortality rates. Abundance of endemic egg predators was measured through direct observation and trapping.Coleomegilla maculata(DeGeer), a coccinellid, was the most abundant predator and the only one consistently present whenever Colorado potato beetle eggs were in the field. Total mortality to eggs from predation was 39.9% in the second generation of 1986 and 37.8% and 58.1% in the first and second generations of 1987, respectively. Daily mortality rate did not change significantly during large fluctuations in prey density. Results suggest thatC. maculatacan contribute to the control of both early and late generations of Colorado potato beetle and efforts to conserve this natural enemy will help reduce the need for chemical control.

DOI:10.1093/ee/20.3.841

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

This study addresses the potential impact of natural enemies on the abundance of spider mites,Tetranychusspp., on cotton in the San Joaquin Valley of California. These natural enemies are omnivorous predators, and include the big-eyed bug,Geocoris pallensStål andG. punctipes(Say), the minute pirate bug,Orius tristicolor(White), and the western flower thrips,Frankliniella occidentalis(Pergande). Simple linear regression suggested that omnivorous predators were potentially effective in delaying the buildup of spider mites, with the highestr2(0.65) recorded for adultF. occidentalis.Geocorisshowed the potential to suppress the rate of spider mite population increase (r2= 0.73). All three tested predator species exhibited the capacity to suppress early season spider mite abundance, with the highestr2(0.62) recorded forGeocorisandOrius. Predators were also potentially able to suppress mid- to late-season spider mite populations. Multiple regression analysis indicated a significant negative correlation between mid- to late-season spider mite abundance and early season predators. Results from a second year were less conclusive, suggesting that the reduced range of spider mite abundance limited our ability to discern potentially significant interactions during that year.

DOI:10.1093/ee/20.3.849

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The natural history, oviposition, feeding behavior, and parasitism ofColeophora caespititiellaZeller andC. cratipennellaClemens in a Rhode Island salt marsh are described.C. cratipennellais univoltine and feeds only on the rushJuncus gerardiLoisel.C. caespititiellais bivoltine; the spring generation larvae feed onJ. gerardiand the fall generation larvae feed on the annualSalicornia europaeaL. This is the first report of bivoltinism in this genus and the first report of a singleColeophoraspecies feeding on plants in these two plant families. InJ. gerardimonocultures, oviposition frequency increased with increasing flowering culm density and flower density per culm. InS. europaeamonocultures, oviposition frequency initially increased with plant density, but moths appear to be satiated by high-densityS. europaeastands. Overall, larvae infested 22% of theJ. gerardiseed capsules and reduced seed set in these infested capsules by 60%.C. caespititiellalarvae consumed from 4 to 25% of the seeds ofS. europaea. Larvae were rarely seen to move from the flowering culm or plant where they were first encountered. Eighteen percent ofC. cratipennellalarvae and 10% of first-generationC. caespititiellalarvae were parasitized by an unidentified ichneumonid wasp. Because these moths feed on two plant species with known asymmetric competitive interactions and consume more seeds of the dominant competitor (J. gerardi), the moths may mediate the competitive interactions betweenJ. gerardiandS. europaea.

DOI:10.1093/ee/20.3.857

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Population density ofMicrorhopala vittata(F.) (Coleoptera: Chrysomelidae), a leaf-miner of goldenrod (Solidago), is low in most old fields, but populations occasionally reach densities at which they severely damage their host plant. A survey of 21 old fields revealed that the beetle was present at all sites. To determine whether development was retarded or mortality was elevated in sites with fewer beetles, growth and mortality were experimentally assessed in three low-density sites and three high-density sites. A major source of mortality was early leaf senescence in sites with taller plants, and in these sites larvae grew more slowly. This form of mortality was not present in all three low-density sites, however, and thus was not sufficient to explain differences in beetle density. Only eulophid parasitism of larvae was more prevalent in the low-density sites. Unexplained mortality of first instars was greater in high-density sites. However, overall egg-to-pupa mortality was not correlated with initial beetle density. The combined effect of several mortality agents may be responsible for maintainingM. vittatapopulations at low densities most of the time. A release from these agents that would allow populations to irrupt may be short-lived and thus difficult to detect.

DOI:10.1093/ee/20.3.865

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The effects of host density and temperature on the functional response of the bethylid parasitoidCephalonomia waterstoni(Gahan) attacking fourth-instar rusty grain beetle,Cryptolestes ferrugineus(Stephens) were examined. Five temperatures and six host densities were used. A type II functional response model was fit separately to each temperature. The maximum attack rate ranged from 7.5 larvae/12 h at 25°C, to 2.9 larvae/12 h at 38°C. Handling time and instantaneous search rate varied with temperature. A new functional response equation was developed in which handling time is a quadratic function of temperature. This equation explained 83% of the variation in attack rate. Although instantaneous search rate was also affected by temperature, it was sufficient to make only handling time a function of temperature because the two parameters were highly correlated.

DOI:10.1093/ee/20.3.872

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Overwinter survival of the boll weevil,Anthonomus grandisBoheman, was compared in the southern and northern Texas Rolling Plains over a 4-yr period. In one test, survival in mesquite (Prosopis glandulosaTorr.) litter was compared to that in broadleaf litter during the winters of 1985–1986, 1986–1987, and 1987–1988. Mesquite litter was a suitable overwintering habitat, and overwinter survival in mesquite litter was comparable to that in broadleaf litter in the southern and northern Rolling Plains. Spring emergence terminated earlier in mesquite litter as compared with that in broadleaf litter in both the southern and northern Rolling Plains. In a second test conducted during the winters of 1986–1989, overwinter survival of four different populations was compared in the southern and northern Rolling Plains. The results of the second test indicated that there are no genetic differences in overwintering ability in Rolling Plains boll weevils. A multiple regression analysis indicated that unique winter weather patterns at each overwintering location were mainly responsible for determining degree of overwintering mortality.

DOI:10.1093/ee/20.3.877

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The natural enemies ofSida acutaandS. rhombifoliain Mexico were surveyedover a period of 3 yr. The phytophagous arthropods collected from these plants belonged to 27 families in six orders. Coleoptera accounted for 48%, Hemiptera 27%, Lepidoptera 16%, Diptera 5%, Hymenoptera 2%, and Acarina 2%. Fifty-eight percent reproduced onS. acutaorS. rhombifoliaor both. Twelve species were considered to have potential as biological control agents for these weeds. One,Calligrapha pantherinaStål, has been released in Australia and is causing extensive defoliation ofS. acuta. Prospects for biological control of these weeds are favorable.

DOI:10.1093/ee/20.3.882

出版商:Oxford University Press    

年代:1991

数据来源: OUP