摘要:

We evaluated the separate and combined effects of velvetleaf,Abutilon theophrasti(Medic), competition and simulated green cloverworm (GCW),Plathypena scabra(F), defoliation on soybean grain yield and components of yield in a 2-year study. Competition durations of velvetleaf were manipulated manually (roguing) and chemically (postemergence herbicide). A temperature-dependent developmental model was used to determine realistically the rate and intensity of simulated GCW defoliation (imposed by hole-punching). Velvetleaf stress was largely limited to soybeans near full-season weeds. As few as 4,386 velvetleaf plants per ha were capable of causing economic losses in soybeans. Increasing the intensity of defoliation resulted in a proportional linear reduction in grain yield. Under the conditions studied, 25 to 29 simulated GCW larvae equivalents per m of soybean row were required to cause economic loss in full-bloom soybeans. At the plot level, little definable evidence of velvetleaf and GCW interaction was detected. On a stratum basis, consistency in velvetleaf-induced yield reductions was observed in the upper two-thirds of the canopy, whereas 2-year consistency in simulated GCW-induced losses was restricted to the lower two-thirds of the canopy. Nonadditive treatment interactions were consistently evident only in the central canopy stratum of soybeans near weeds. This study indicates that knowledge of velvetleaf prevalence in a field probably is not a prerequisite for using conventional monospecific economic injury levels in managing the GCW on fullbloom soybeans, assuming that a runaway velvetleaf infestation is not present.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.917

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

The humidity of the microhabitat of leaf-inhabiting arthropods can vary greatly with respect to atmospheric humidity. Any models or assumptions made about the impact of atmospheric humidity on these arthropods need to take into account the humidity within the leaf boundary layer. We present a model which estimates the humidity within the leaf boundary layer, as long as the leaf temperature, ambient temperature, and ambient humidity are known.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.926

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

The relative impact on soybeans of 24 arthropod species in 18 states is analyzed using the multivariate technique of reciprocal averaging (RA). This ordination technique is related to both weighted averages and to principal components analysis and other eigenvector techniques. The advantages of RA are discussed in comparison to results obtained by cluster analysis. RA is a useful method in the analysis of complex entomological data.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.930

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Aphytis melinusDeBach responded significantly more to green and yellow traps than to white, blue, fluorescent yellow, clear, black, or red;Scirtothrlps citri(Moulton) responded significantly more to fluorescent yellow, than to any of the other colored polyvinyl rectangular traps.A. melinusdid not distinguish between opaque and translucent colored rectangles nor between different trap shapes.S. citriresponded significantly more to translucent yellow and green than to opaque yellow and green.S. citrialso preferred triangular, elliptical, and rectangular shapes over circular and square ones. Smaller traps were significantly more efficient in trappingA. melinusthan the 386.1-cm2rectangular traps; however, there was no significant difference betweenS. citricatches on the basis of number per unit area.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.935

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Sampling adultPhyllotreta cruiciferae(Goeze) andP. striolata(F.) overwintering in a grove of trees gave estimates of combined mean densities as high as about 2 million beetles per ha. Both species showed a similar aggregated type of distribution. Variation in the numbers of adults obtained among sampling areas suggests that too many samples would be required for winter sampling to be a practical method of estimating flea beetle abundance over large areas.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.941

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Rivellia quadrifasciata(Macquart), the soybean nodule fly (SNF), was reared in the laboratory on detached soybean nodules and in the greenhouse on intact, nodulated root systems of hydroponically grown soybean plants. In greenhouse experiments, significantly more SNF individuals were reared from egg to adult on potted plants of a nodulating soybean near isoline than on its nonnodulating counterpart. Southern pea (Vigna unguiculata) was identified as a new host for larvae by using adult emergence cages. In naturally infested field plots, significantly more adults emerged from southern peas than from soybeans, and none emerged from peanuts or snap beans. Well nodulated soybeans were superior hosts, as compared to poorly nodulated soybeans.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.945

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Kromecote® or water-sensitive cards were placed at three or four vertical levels within the canopy of wide (96.5–101.1 cm) and narrow (17.8–25.4 cm) rows of soybeans,Glycine max(L.) Merrill, to measure spray penetration and droplet characteristics of insecticides applied with aerial or ground equipment. Larval mortality data were used to measure the efficacy of the insecticides at three vertical strata within the two row-spacing systems. The size of the droplets deposited was generally smaller within all levels of the narrow-row canopy compared to the wide-row canopy. The total number of drops per cm2and mean percentage of coverage was reduced in the narrow-row spacing compared to the wide-row spacing, but only within the median one-third of the canopy. Similarly, the percentage of larval mortality was reduced within the median one-third of the narrow-row plots compared to the wide-row plots at the same level. The variable combination of drops per cm2and number median diameter was significantly correlated (R= 0.6535) with the percentage of reductions of lepidopterous larval populations of the soybean looper,Pseudoplusia includens(Walker), velvetbean caterpillar,Anticarsia gemmatalisHübner, and green cloverworm,Plathypena scabra(Fab.).

ISSN:1754-5692    

DOI:10.1093/ee/13.4.948

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Cage studies were conducted in the field in order to evaluate the effectiveness of entomophagous arthropods in reducing noctuid pest populations in soybeans. First and second-stage noctuid larvae were distributed randomly on soybean plants and exposed to single predator species and predator complexes for 4 to 9 days. In tests with single species in which densities of adult predators and prey varied,Oxyopes salticusHentz took 7.4 larvae,Nabis roseipennisReuter took 6.2 larvae,Geocoris punctipes(Say) consumed up to 3.4 larvae,Pardosa spp.took 3.3 larvae, andLebia analisDejean took 1.8 larvae per adult before larvae became too large for the predators to consume. When noctuid larvae at densities of 30 to 180 per cage were exposed to two complexes of predators, the number of prey taken by each complex was positively correlated with prey density. Slopes of regression lines revealed the complexes of predators consumed 0.26 and 0.47 larvae/week for each larva placed on caged plants. This study provides additional evidence that predaceous arthropods are of economic value to soybean growers.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.954

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

During 2 years of field experiments, five crops showed consistent differences in their response to the seedcorn maggot,Delia platura(Meigen). Watermelons and cantaloupes showed greatest stand losses, snap and lima beans were intermediate, and sweet corn appeared to be unaffected despite a seed infestation level of at least 50%. More than twice as many seedcorn maggot larvae and pupae were collected from lima beans than from the melon crops. The smallest number of larvae and pupae were taken from plots where no seeds were planted. In these plots seedcorn maggots that were present either immigrated before pupation or developed on organic soil debris and weed seeds. In 1982 the bean and corn plots produced heavier pupae than the melon plots. Thus, seedcorn maggot populations may build up more rapidly in bean and corn crop areas than in those planted with melons, although stand loss may be more evident in the latter.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.962

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Mated female lesser cornstalk borer (Elasmopalpus lignosellus[Zeller]) moths were held in constant temperatures ranging from 17 to 35°C to determine the effect of temperature on oviposition and longevity. Over the temperature range tested, adult female longevity decreased linearly as temperature increased. Total fecundity (total number of eggs laid per female) and average oviposition rate (total fecundity at a given temperature divided by the average longevity at the same temperature) varied nonlinearly with temperature. A two-independent-variable polynomial response surface significantly described effects of temperature and female age on daily oviposition rate. Maximum egg production occurred between 27.5 and 30.5°C.

ISSN:1754-5692    

DOI:10.1093/ee/13.4.966

出版商:Oxford University Press    

年代:1984

数据来源: OUP