摘要:

The spatial distribution of soil microarthropods in soybean fields was investigated by use of a modified Tullgren extractor. Blocks of soil were extracted over a grid of collection cells from which microarthropod aggregations could be identified and measured. Aggregations in conventionally tilled soybeans were smaller than those in no-tillage soybeans, and had less influence on population distributions. Population size was highly correlated with the area of soil microarthropod aggregations.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1303

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Fourteen types of overwraps on raisin or prune cartons were tested for insect resistance against nine species of stored-product insects. They were classified into three categoriesof seal tightness. The most insect-resistant overwrap on a raisin carton was a D.9-mil, heat seal-coated, biaxially oriented polypropylene film, and the most resistant prune carton overwrap was a 2.5-mil, polyethylene-coated foil overwrap. Raisin cartons of all types of overwraps classified in the tight-seal category averaged 18.7% infested, whereas prune overwraps in the same category averaged 8.2%. The averages in the tight-seal category were lower than infestation rates of any type of film individually; thus, a tightly sealed overwrap was more important than the type of overwrap used.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1310

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

The tachinidLixophaga diatraeae(Townsend) senses the larviposition host (sugarcane borer,Diatraea saccharalis)frass by tarsi rather than by antennae. Methanol extraction of the host larvae frass, followed by column and thin-layer chromatography, indicated activity in the polar nonvolatile components. Similar extraction of sugarcane stalk produced an equally active larviposition stimulant having the same chromatographic properties as the frass extract. The active fractions of both frass and sugarcane did not contain sterols, reactive unsaturation, or protein. Qualitative tests showed the presence of phenols, alcohols, and carbohydrates. The tachinid was equally active to a dichloromethane extract of paraffin wax and standard hydrocarbons alone and in combination.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1312

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

The selection of plant species used by the range caterpillar,Hemileuca oliviaeCockerell, for feeding, pupation, and oviposition in the short-grass prairie habitat of Lincoln County, N.Mex., was studied in relation to the assortment of plants available in three plant communities found along a hillside. Larvae were polyphagous; feeding larvae were distributed randomly on grasses in two of the three communities, with only small departures from randomness found in the third community. Major departures from random distributions during pupation and oviposition were due to selection by larvae and adults of structures that would provide adequate physical support for these stages. Selection during pupation and oviposition did not reflect any broad taxonomic associations among the plant species, but rather certain physical attributes, such as a stiff upright habit.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1315

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Infection rates ofZoophthora phytonomi(Arthur) Batko in alfalfa weevil,Hypera postica(Gyllenhal), larvae were monitored from 1979 through 1981 in Rockbridge County, Va. Infection rates of the pathogen were highest near the end of the spring alfalfa crop when alfalfa weevil larval populations were declining.Z. phylonomiwas effective in suppressing alfalfa weevil populations below economic threshold levels only during a period of higher rainfall that occurred in 1979. A negative correlation between infection rates ofZ. phytonomiand parasitization rates of the ichneumonidparasiteBathyplectes anurus(Thomson) (Hymenoptera: Ichneumonidae) suggests a possible interference between these two natural control agents.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1318

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Egg and larval parasitism of the tomato pinworm (TPW),Keiferia lycopersicella(Walsingham), was studied in southern Florida tomato fields. Larval parasitism ranged from 39.34 to46.26%cin 1980–1981.Apantelesspp. was the most abundant larval parasite, followed bySympiesis stigmatipennisGirault andTemeluchaspp. Egg parasitism byTrichogramma pretiosumRiley ranged from 33 to 92% in fields with low egg density (less than one egg per two leaves) and from 12 to 60% in fields with high egg density (more than three eggs per two leaves). Despite this,T. pretiosumwas considered density independent of TPW population. Parasites were most abundant in abandoned fields from April through June.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1322

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Several daylight fluorescent-painted rectangles, 15 by 20 cm, effectively monitored pear psylla adults on pears. Both hue and intensity of reflection appear to be important for eliciting positive response by pear psylla adults to visual traps. The greatest captures occurred for hues with reflection peaks in the 520 to 600-nm range of the spectrum, which is the same range of pear foliage itself. Captures of adult pear psylla on visual traps of most hues or shades were significantly greater than those obtained by standard limb-jarring methods. In addition, captures of pear psylla adults on lightning yellow and arc yellow traps were beller correlated with the occurrence of eggs and nymphs on pear spurs and sooty-mold blemishing on fruits than counts obtained by limb jarring.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1327

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Experiments were conducted to determine the effects of hunger on the functional response of femaleGeocoris bullatus(Say) to the combined density of two species ofLygusat three temperatures (15, 25, and 35°C). Models published by Holling and Rogers were fit to these data to predict values of handling times and searching rates. Observed handling times were much shorter than predicted handling times in all cases. Searching rates varied as the predator was starved. A simulation model incorporating handling time, searching rates, and hunger predicted acceptable rates of predation except when prey were very abundant. Under these conditions, observed rates were lower than predicted rates, probably because the predator spent most (71%) of its time in a small (32%) part of the arena.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1332

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Weight change of alfalfa weevil larvae infected with anEryniafungus was compared with that of noninfected larvae at different saturation deficits. As expected, the developing fungus was generally sensitive to changes in atmospheric water concentration. Weight loss of infected larvae decreased as saturation deficit levels decreased. Typically, percent weight loss of infected larvae was>percent weight loss of noninfected dead larvae during the ca. 7-h period between rhizoid emergence and initial conidial discharge. Above 1.5-mm-Hg saturation deficit, infected larvae in the weight tract experiments formed rhizoids and pseudocystidia but not conidiophores. The data suggested a water loss threshold (based on weight change) for conidiophore emergence in the 1.5- to 1.8-mm-Hg saturation deficit range. Overall, infected larvae lost more water than did noninfected dead larvae. This was primarily due to loss of cuticle integrity and increased surface area available for evaporation. Based on these factors and the shape of the weight track for infected larvae, it was inferred that diffusion processes are highly influential to maintenance and development of conidiophore production.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1339

出版商:Oxford University Press    

年代:1983

数据来源: OUP

摘要:

Eryniasp. conidiation on larval alfalfa weevil,Hypera postica,was studied in the laboratory under constant and fluctuating saturation deficits. At optimum conditions of saturated still air (0.0 mm of Hg, 100% relative humidity [RH]), the fungus would discharge conidia for up to 50 h. Peak conidial discharge occurred ca. 3 h after exposure to saturation deficits up to 0.9 mm of Hg. Minimal conidial discharge occurred at 1.8 of mm Hg saturation deficit. Periodic intervals of high-saturation deficits had increasingly repressive effects on both conidial discharge rate and duration as saturation deficits during these intervals increased. However, the fungus had the ability to resume conidial discharge if the environment was returned to optimal and<15 h had elapsed. Wind, at 4 liters/min with an RH of 90%, had an almost identical effect on conidial discharge repression as still air at 75.6% RH.

ISSN:0046-225X    

DOI:10.1093/ee/12.5.1344

出版商:Oxford University Press    

年代:1983

数据来源: OUP