摘要:

Cotesia marginiventris(Cresson),Diolcogaster facetosa(Weed), andRogas nolophanaeAshmead, which respectively parasitize progressively older green cloverworm,Plathypena scabra(F.) larvae, produced (x¯± SE) 362.7 ± 24.1, 83.2 ± 11.4, 66.3 ± 6.1 offspring, respectively, during their lifetimes. Adult female longevity at 24°Caveraged 18.1 ± 0.8, 13.0 ± 0.9, and 29.9 ± 2.7 d for these species, respectively. Numbers of mature eggs from dissections of 2-d-old females were 105 ± 7.1, 57 ± 5.9, and 5.2 ± 0.9. Primary braconid and tachinid parasitoids of the green cloverworm exhibited decreasing observed or estimated fecundities with respect to increasing age of host larvae attacked. Decreasing fecundities of these parasitoid species may reflect increasing potential for survival until time of parasitoid emergence of the progressively older host larvae which these species attack. Other factors suggested as influencing fecundity are breadth of host range and complexity of host location, capture, and oviposition behaviors.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.349

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Effects of four plant populations and intercropping beans with maize on the population patterns of bean flies (Ophiomyia phaseoliTryon,O. centrosematisde Meijere, andMelanagromyza spencerellaGreathead) on common beans were studied. Percentage of plants infested by bean flies was significantly less in the one-third beans and two-thirds maize intercrop combination than in pure stand beans. The incidence of bean flies decreased with increasing plant populations from 66,666 to 533,332 plants per ha. Ovipunctures made by bean flies in the leaves of beans were not significantly different among the various treatments. A significant and gradual decrease in the number of ovipunctures from lower to higher plant populations was recorded. The bean fly larva–pupal counts were significantly lower in both intercrop combinations than in pure stand beans; larval–pupal counts were significantly lower in higher plant populations in 1983 season. Possible reasons for population patterns of bean flies are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.354

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Weeds in a Louisiana sugarcane field increased the abundance of arthropod prey and predators (including the imported fire ant), and caused at least 25% less injury from sugarcane borer,Diatraea saccharalis(F.). Weed competition, however, reduced sugarcane biomass, stand density, and sugar yields. Without insecticidal control of sugarcane borer, weedy habitats were more profitable than weed-free habitats. Future study on weed conservation in the furrows alone is suggested. Spring aldicarb (nematicide–insecticide) applications reduced arthropod prey, particularly stylet-feeding herbivorous insects, for up to 10 wk. Regardless of weed cover, predator densities on the soil surface, weeds, and cane stalks were decreased by the nematicide, and percentage of internodes injured by sugarcane borers increased by at least 19%. Fenvalerate (insecticide) reduced predators and prey arthropods on the soil surface and cane stalks, includingSolenopsis invictaBuren. Cicadellidae on cane foliage were reduced by the insecticide, but the yellow sugarcane aphid,Sipha flava(Forbes), was enhanced by 63%. Fenvalerate did provide at least 70% protection against the sugarcane borer, with ratoon crop sugar yields 8.7% greater than in the insecticide-free regimes. A combination of weed and sugarcane borer chemical control tactics was the most economically sound pest management strategy.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.358

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The spatial and temporal larval distributions of the newly recognized potential pest of boreal forests,Korscheltellus gracilis(Grote), are presented. Larvae were collected from 17 of 20 areas in the Green Mountain National Forest, Vermont, and highest densities were at elevations>1,000 m. On Camels Hump Mountain (Huntington, Vt.), larval density during the summer of 1987 was approximately 440,000 ± 36,000 per hectare. Changes in density between May and August 1987 were not detected. Larvae were clumped in space and most abundant in the upper 9 cm of soil. Data from head capsule measurements suggest at least six instars.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.371

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The International Pheromone Systems Universal moth trap (Unitrap), when baited with the pheromone of fall armyworm,Spodoptera frugiperda(J. E. Smith), has intermittently been observed to capture large numbers of bumblebees in addition to fall armyworm males. Studies were undertaken in Graham County, N.C., in 1988 and 1989 to determine the contributing factors. Investigation revealed that the yellow color of the traps was attractive to bumblebees, but the color alone did not influence their subsequent movement into the trap and resulting capture. Fall armyworm pheromone alone, particularly when used in combination with a No-Pest resin strip containing dichlorovos insecticide (to kill trapped insects), significantly increased the capture of bumblebees in yellow Unitraps. The green Unitrap alone was totally unattractive to bumblebees. Unitraps captured the greatest number of bumblebees when positioned adjacent to, and at the same height as, pollinating corn tassels. The number of captured bumblebees declined progressively as Unitrap height was lowered at 1-meter intervals from 4 to 1 m. Eleven species of bumblebees were identified from Unitrap captures. Abundant early spring rainfall in 1989 appeared to be primarily responsible for substantial reductions in the number of ground-nesting species of bumblebees during the summer.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.377

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

During 1986–1988, sampling to estimate population densities of the citrus rust mite,Phyllocoptruta oleivoraAshmead, on fruit in individual citrus trees was investigated. A sample unit was a 1-cm2surface area anywhere on a fruit except within areas receiving maximum sun exposure or at the point of the fruit closest to the trunk. Citrus rust mites were usually aggregated on and among fruit within individual citrus trees, and the degree of aggregation generally increased as levels of mites increased. Frequency distributions for the number of mites per two-sample units per fruit usually followed the negative binomial distribution, withkvalues from 0.1 to 4.2 ($\bar x$= 0.53, an estimated commonkwas 0.593). Aggregation by citrus rust mites was similar within ‘Hamlin’ (n= 231 trees) and ‘Valencia’ (n = 172 trees) across a wide range of densities of mites per square centimeter; levels of mites were low in the ‘Pineapple’ orange trees (n = 10) and ‘Marsh’ grapefruit trees (n= 30) sampled, but aggregation by citrus rust mites within these trees was similar to within ‘Hamlin’ and ‘Valencia’ trees. Fewer mites were often present in the west quadrant of trees. Average densities of mites per square centimeter on fruit in individual trees were estimated using 20 fruit samples per tree and two subsamples per fruit, with the fruit spaced evenly around the canopy at 0.3 to 2.1 m above the ground. Relative variation of estimates was large when the density of mites was small but decreased as densities increased. Optimum sample sizes per fruit and per tree therefore varied at different densities. Analyses of variance components indicated that standard errors associated with sampling 25 fruit with one subsample per fruit would be equivalent to those associated with sampling 20 fruit with two subsamples per fruit. Expected standard errors and relative variation for a wide range of sample sizes per tree were examined.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.382

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Within-plant distribution of squash bug,Anasa tristis(De Geer), adults and egg masses on spring plantings of summer squash was determined by making whole-plant visual examinations. A significantly greater percentage of adults was found on the soil surface than on plants in early stages of crop phenology (90% of squash bug oviposition occurred on abaxial leaf surfaces. A significantly greater percentage (90%)of egg masses was deposited on leaves in the lower one-half of plants during vegetative plant growth. Average weighted mean egg mass location on plants was found to be highly correlated (P<0.01) with the number of leaves per plant. Results of this study suggest that sampling procedures should be developed separately for adults and egg masses. Monitoring for adults should include examination of both the plant and soil surface, whereas sampling for egg masses should concentrate primarily on the lower foliar canopy.

ISSN:1754-5692    

DOI:10.1093/ee/20.1.391

出版商:Oxford University Press    

年代:1991

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/20.1.396

出版商:Oxford University Press    

年代:1991

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/20.1.397

出版商:Oxford University Press    

年代:1991

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/20.1.398

出版商:Oxford University Press    

年代:1991

数据来源: OUP