摘要:

Control of the desert termiteGnathamitermes tubiformans(Buckley) in a shortgrass prairie in W Texas resulted in an improvement in the watershed value and soil-water relationships for forage plants. The percentages of>1-mm soil aggregates were greater on termite-free soils, whereas percentages of<1-mm aggregates were greater on termiteinfested soils. Organic carbon, forb production, and litter accumulation increased significantly on termite-free soils. Capillary pore space was normally higher in termite-free soils, while non-capillary pore space was normally higher in termite-infested soils. Termite control had no effect on total pore space, hydraulic conductivity, and bulk density in the soil studied. Rainfall infiltration was greater on termite-free soils after the 1st 15 min of a simulated rainstorm. Runoff and sediment load were greater on termite-infested rangeland than on termite-free rangeland. Evapotranspiration was greater on termite-free soils during a 7-day period following rainfall application. However, termite-free soils retained more moisture during dry periods than termite-infested soils.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.899

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

A system model for woodland poolAedeswas constructed and a computer simulation implementing the system model was constructed and refined for populations ofA. stimulans-fitchiimosquitoes. Information and data utilized in the model construction were obtained from surveys conducted in Michigan state parks and an extensive literature review. Dynamics of the mosquito's life cycle and of the woodland pool ecosystem were modeled and the resultant equations are described. Assumptions used in the modeling process are briefly discussed in order to show the reasoning process underlying the use of these equations in the simulation. A description of computer program structure and data files utilized by the program is given. Research on and refinement of the physical components consisted of measurements during 1973 on aquatic parameters chosen as key factors in immature mosquito dynamics and meteorological features oriented as stimuli to these parameters. The resultant data were statistically analyzed to obtain the best available model for maximum water temperature, dissolved oxygen concentration and water depth.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.905

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

Commercial corn hybrids were tested to assess several field and greenhouse techniques of evaluating corn rootworm tolerance. Root-system size and secondary root ratings obtained in the field correlated well with percentage root lodging in the field. Rootsystem size ratings obtained in the greenhouse were highly correlated with those ratings obtained in the field. Greenhouse evaluations effective detected differences among hybrids for root-damage rating, a measure of antibiosis, but field evaluations did not. Hybrids did not differ significantly for the amount of yield reduction incurred from rootworm injury.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.920

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

When the overwintering eggs of European red mite,Panonychus ulmi(Koch), were recorded according to their location at or near nodes of randomly collected apple (var. Red Delicious) twigs:(a) the logarithms of the egg counts provided the most useful measurement for studying the infestation;(b) the total number of eggs, i.e., colored plus uncolored, was the most satisfactory unit to use in the log transformation;(c) the ratio of colored to uncolored eggs was 1.27 at the time of sampling; and,(d) the ratio of colored to uncolored eggs varied between Red Delicious twigs (ranging from 1–7 depending on the twig).A formula was developed for comparing the degree of mite, infestation of apple cultivars. The best and most consistent results were obtained when 13 nodes above and 8 nodes below the budscale scar were sampled. Precision can be improved by increasing the number of twigs sampled.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.923

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

Gypsy moth kairomones influencing host recognition responses of two species of hymenopteran parasitoids, the chalcicidBrachymeria intermedia(Nees) and the braconidApanteles melanoscelus(Ratz.) were recovered from the gypsy moth,Porthetria disparL. A kairomone forB. intermediawas removed by washing gypsy moth pupae with hexane. The pupal wash, when exposed on filter paper toB. intermediafemales, elicited an antennal response characteristic of adults when they find host pupae. A kairomone forA. melanosceluswas obtained by washing gypsy moth larvae with hexane. ForA. melanoscelus, antennal responses were recorded with hexane washes of gypsy moth larvae, but not of pupae, and forB. intermedia, responses occurred with hexane washes of pupae, but not of larvae. Work on identification of the kairomones is in progress.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.929

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

Bathyplectes curculionis(Thomson) cocoons containing diapausing larvae were planted in alfalfa fields and recovered at monthly intervals from June 1974 to June 1975 to determine field mortality factors. Absolute density samples of cocoons also were taken during the summer, fall, and early spring to measure survivorship in an actual field population.Invertebrate predation on diapausingB. curculioniscaused greater mortality to the parasites than the combined effects of other mortality factors such as weather, hyperparasites, and insecticide spraying. Heat kill in the summer may be a significant factor in warmer areas of the parasite's range. The overall survivorship of the diapausing larval population from early summer 1974 to the following spring was 15.9±5.3% S.E. Our findings show that invertebrate predators may substantially reduce parasite populations in a field crop.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.931

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

The elm spanworm,Ennomos subsignarius(Hübner), is known to be more vigorous and develop faster when reared on juvenile rather than mature leaves of the hickories,Caryaspp., and oaks,Quercusspp., two of its principal hosts in the Southern United States. Seasonal changes in the quantities of two groups of insect nutrients—fatty acids and sterols—were therefore determined in the foliage of pignut hickory,Carya glabra(Mill.) Sweet, and southern red oak,Quercus falcataMichx. var.falcata. In decreasing order of concentration, the major fatty acids found in both species were linolenic, palmitic, linoleic, oleic, myristic, and stearic. Except for the latter two, which remained consistently low throughout the growing season, these fatty acids generally decreased in concentration with the maturation of leaves of both species. In both species, concentrations of sterols varied little throughout the growing season except in foliage only a few days old. Sitosterol was the dominant sterol in both species. Stigmasterol and campesterol were present in relatively low and equal concentrations. Fatty acids in the foliage of tulip-poplar,Liriodendron tulipiferaL., which is not a host of the spanworm, followed the same pattern as in the two host species, but the amounts were twice as great.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.935

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

Male attraction to the sex pheromone, (E)-9-dodecenyl acetate, of the European pine shoot moth,Rhyacionia buoliana(Schiffermüller), is suppressed if lure formulations contain the geometrical isomer in proportions as low as 3%. However, spatial dispersion of the inhibitory isomer around pheromone or virgin-female-baited traps did not prevent male orientation. In contrast, when the pheromone alone was released around baited traps in identical plots, male orientation to the traps was successfully disrupted. These findings suggest that forR. buolianathe actual pheromone is superior to inhibitory compounds for mating disruption on an area-wide basis.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.944

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

The parasitic waspPediobius foveolatus(Crawford), was successfully reared in the laboratory onEpilachna varivestisMulsant. The feasibility of maintaining overwintering stocks of this parasite was demonstrated. The optimum parasite-host ratio used in terms of adult parasites produced/host larvae was 0.4:1. Reproductive capacity of adult ♀ diminished with age, and those held for longer than 90 days at 13°C failed to successfully reproduce. The optimum age for reproduction was less than 12 days.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.953

出版商:Oxford University Press    

年代:1975

数据来源: OUP

摘要:

As the population of green peach aphids (GPA),Myzus persicae(Sulzer), declined on peach trees, another population increased on lambsquarters,Chenopodium albumL., and pigweed,Amaranthus retroflexusL., on the floor of the orchard. In 1973 and 1974 we estimated that roughly 3–16 million aphids/acre were produced on the floor of a peach orchard. The same weed hosts inspected 1–6 miles away from peach orchards indicated a substantial decrease in the number of GPA. However, a survey in the fruitgrowing area showed that apple orchards in proximity to peach orchards had as many GPA on the same weed hosts as in peach orchards. Orchard grass used as a ground cover will greatly minimize the number of suitable weed hosts of the GPA.

ISSN:0046-225X    

DOI:10.1093/ee/4.6.958

出版商:Oxford University Press    

年代:1975

数据来源: OUP