摘要:

Monochamus carolinensis(Olivier) beetles infested with the pinewood nematode,Bursaphelenchus xylophilus, were tethered and flown upon emergence from host logs. The mean (±SD) number of nematodes carried per beetle was 7,933 (±16,997) with a mean flight time of 18.6 (±11.4) min. Larger beetles exhibited longer flights and carried more nematodes. The density of nematodes in the beetle had a slight negative influence on flight capability. The sex of the beetle had no effect on flight duration or the number of nematodes carried.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.670

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Hourly captures of male black cutworms,Agrotis ipsilon(Hufnagel), in traps baited with different ages of virgin females (2, 4, 6, and 8 d) were examined during three phases of phenology in Iowa: migration–infestation, early postinfestation, and mid-postinfestation. Six-d-old virgin females captured the most males during migration-infestation, whereas traps using 4-d-old females, although not statistically significant, captured the most males during early postinfestation. Two factors, greater capture rate and longer capture period, were responsible for the enhanced attractiveness of 6-d-old females during migration–infestation. Only capture rate contributed to increased attractiveness of 4-d-old females during early postinfestation. Trap captures during mid-postinfestation were extremely low despite active calling by females and possibly reflected the beginning of reproductive diapause in males. Nocturnal rhythms of capture were similar across virgin female ages and seasons. Likewise, comparisons with a trap baited with synthetic pheromone revealed similarities that suggest that the nightly rhythm of mating activities is mediated primarily by the male.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.674

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The spatial arrangement of needle fascicles on slash pine shoots consisted of 21 fascicles in a spiral that turned around the shoot eight times before repeating itself. This cyclic unit was used to map the distribution of narrow, non-egg-bearing slits (“probes”) and egg-bearing pockets made by femaleNeodiprion merkeliRoss in the foliage of one large, heavily infested shoot. Females exhibited a strong apical response in reference to growth flushes on the shoot and a 5:1 preference for accepting the needles of two-needle rather than three-needle fascicles for oviposition. In 47 lightly infested shoots, the mean number of eggs laid per needle was 30% greater in needles from two-needle fascicles but increased with increasing needle width for two- and three-needle fascicles. The incidence of single probes unaccompanied by oviposition in the same needle was 28 times higher in needles from three than two-needle fascicles, a difference attributed to the relatively narrow flat-side width of needles available for oviposition in some three-needle fascicles.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.678

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Effects of interactions among temperature (20, 25, and 30°c), known resistant and susceptible corn genotypes (‘Zapalote Chico’ and ‘Stowell's Evergreen’), and concentrations of corn silk material–pinto bean diet mixture (0 and 18.75, 37.5 and 67.0 mg) on corn earworm,Heliothis zea(Boddie), growth and developmental parameters were evaluated. Parameters measured were: 9-d larval weights, developmental time of larvae, weight of pupae, and days to adult eclosion. Corn earworm growth was slowest at 20°C and fastest at 30°C. Significant (P>0.05) differences caused by the resistant ‘Zapalote Chico’ compared with the susceptible ‘Stowell's Evergreen’ were measured consistently at 25°C for all four developmental parameters. The median temperature (25°C) appears to be optimum for detecting growth differences between resistant and susceptible plant materials regardless of silk concentration.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.683

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Seedlings of four wheat cultivars were infested with virulent and avirulent Hessian fly,Mayetiola destructor(Say), biotypes. The presence of a single virulent larva resulted in an alteration of resistance in the plant, allowing survival of all normally avirulent larvae that concurrently or subsequently infested the plant. This phenomenon makes possible the genetic loading of a fly population with potentially large numbers of avirulence genes and could, in part, account for the durability of resistance genes following the release of flyresistant wheat germ plasm in agricultural systems. Previous infestation with avirulent larvae did not affect the plants' susceptibility to subsequent infestation by virulent biotypes.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.687

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Studies were conducted to determine the potential of a synthetic sex pheromone that attracts only males for monitoring sweet potato weevil,Cylas formicarius elegantulus(Summers), populations in southern Florida. Mean weevil counts in plastic funnel traps baited with 10 μg of pheromone and placed in different commercial plantings of white-fleshed sweet potato,Ipomoea batatas(L.) Lam. cv. Picadito, ranged between 2 and 5,785 males per trap per night. Temporal patterns of weevil counts were cyclical, probably because of emergence of new weevil generations following monthly insecticide applications. Mean weevil counts in volunteer fields ranged between 27 and 4,413 per trap per night indicating that volunteer fields harbor dense weevil populations. Spatial statistics indicated that male populations were aggregated. The number of plastic funnel traps required to estimate weevil density reliably was too high to be practical at 10–15% precision levels, but was practical at a 25% precision level. Plastic funnel traps caught significantly more weevils (90–97% of the total catch) and were significantly more efficient (85% efficiency) at catching males than screen-cone boll weevil traps (3–10% of the total catch and 49% efficiency).

ISSN:0046-225X    

DOI:10.1093/ee/18.4.691

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

During 1984 through 1986, eggs ofHeliothis zea(Boddie) andH. virescens(F.) were collected from field-grown tomato accessions varying in levels of glandular trichome-based resistance toManduca sexta(L.) (Lepidoptera: Sphingidae) andLeptinotarsa decemlineata(Say) (Coleoptera: Chrysomelidae). Eggs were subsequently held in the laboratory to determine levels of egg parasitism, mortality, and hatch. Parasitism of eggs byTrichogramma petiosumRiley andT. exiguum(Pinto and Platner) was greatest on theLycopersicon esculentum(Mill) cultivar susceptible toM. sextaand was lowest on all backcross lines (L. esculentum× PI 134417) × PI 134417) and the highly resistantL. hirsutum f. glabratumC. H. Muller (PI 134417). Regression analyses indicated that trichome density accounted for the greatest proportion of variance inTrichogrammaspp. parasitism of eggs. However, because the methyl ketones 2-tridecanone and 2-undecanone, which contribute to the insect resistance of PI 134417, occur in the glandular trichome tips, their effects on parasitism byTrichogrammacould not be separated from the effects of trichome density in this study. Egg density, canopy volume, and number of stem terminals per plot were unrelated to the percentage of parasitism by theTrichogrammastudied here.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.698

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The reduced fitness sometimes associated with resistant alleles has often been discussed as a possible tool of resistance management. A strain of Colorado potato beetles (Leptinotarsa decemlineata(Say)) from Massachusetts resistant to permethrin and azinphosmethyl produced 0.49 times as many larvae and 0.47 times as many adult females as a North Carolina susceptible strain. It also had a mean development time 3.5 d longer than the susceptible strain, resulting in a fitness value (intrinsic rate of increase) of 0.76 relative to the susceptible strain. An azinphosmethyl-resistant strain selected from the Massachusetts resistant strain but containing approximately 94% susceptible genome had a similar decrease in larvae and adult females (0.56 and 0.51 times, respectively) and an increased mean development time of 1.5 d. It was calculated to have a fitness value of 0.83 relative to the susceptible strain. However, azinphosmethyl-resistant heterozygotes (F1) showed no fitness disadvantage compared with the susceptible strain. Additionally, a permethrin-resistant strain also selected from the Massachusetts resistant strain and the permethrin-resistant heterozy-gotes (F1) showed no reduction in fitness relative to the susceptible strain. The implications of the reduced fitness due to the azinphosmethyl-resistance allele as a possible means of resistance management for Colorado potato beetle are discussed.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.705

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Chemical exclusion of predators with permethrin was used to test the effectiveness of the phytoseiid predatorAmblyseius limonicusGarman and McGregor and a complex of minor predators in the biological control of tetranychid (Mononychellusspp.,Tetranychusspp., andOligonychus peruvianusMcGregor) pests of cassava,Manihot esculentaCrantz.Mononychellusspp. andTetranychusspp. populations were significantly higher and predator populations significantly lower in permethrin-treated plots than in control plots. Numbers ofO. peruvianuswere not affected by permethrin. Yield of fresh commercial roots and of dry matter was significantly higher in plots with predators than in plots where permethrin was applied every 2 wk for predator exclusion. Yields of neither fresh nor dry matter in control plots were significantly different from yields in plots that had been protected with acaricide, suggesting that predation kept spider mite populations below economically damaging levels.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.711

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Oviposition byTrichosirocalus horridus(Panzer) onCarduusthistles treated with low dosages of a commonly used herbicide for thistle control, 2,4-dichlorophenoxyacetic acid (2,4-D), was examined in greenhouse and small-plot field studies. Ovipositing weevils placed in cages in the greenhouse with rosettes treated with 5% of the recommended field dosage (1.68 kg/ha) responded to deteriorating leaf condition as a result of 2,4-D treatment rather than to the presence of the herbicide. Fewer eggs were laid in drying or dead leaves than in healthy leaves. Egg viability and larval mortality were not affected by the herbicide. In field studies, oviposition was not different between thistles sprayed with 15% of the recommended field dosage of 2,4-D and control; musk thistle was preferred over plumeless thistle for oviposition.

ISSN:0046-225X    

DOI:10.1093/ee/18.4.715

出版商:Oxford University Press    

年代:1989

数据来源: OUP