摘要:

Adult diet significantly affected the longevity ofUrophora affinisFrauenfeld andUrophora quadrifasciataMeigen. A diet of undiluted honey supplemented with free water was the most favorable, with both species living for ≈30 d. Flies lived from 12 to 14 d on a honey + yeast hydrolysate (1:1) solution and ≈8 to 10 d on distilled water alone. Flies provided with a yeast hydrolysate + water solution lived 6.2 d, which was not significantly different from longevity of flies provided with neither food nor water (5.6 d). When the yeast hydrolysate concentration was reduced, fly longevity increased. In diet choice preference tests, a significant preference for honey was demonstrated for both fly species when compared with a water + yeast hydrolysate (1:1) solution and a water + honey + yeast solution (1:1:1). Similar results were obtained with diets containing more dilute concentrations of yeast.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.623

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

In each of three field releases, a higher percentage of large, mass-reared, sterile Mediterranean fruit flies,Ceratitis capitata, was recaptured than either medium-sized or small flies, with large flies tending to be caught over a longer time period than small flies. Larger flies had a higher emergence rate and percent flight ability. Also, larger flies were significantly longer lived than smaller flies when deprived of food and water in laboratory quality control tests.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.629

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Available evidence suggests thatDalbulus maidis(DeLong&Wolcott), the major vector of the corn stunt spiroplasma,Spiro plasma kunkelii, overwinters as an adult and has no breeding hosts other than theZeaspecies (maize and teosintes). Over the dry season, these breeding hosts are often absent, and, although feeding hosts may be available in some habitats, the vector may migrate mid-winter, or both, we argue thatD. maidiscan spend part or all of the dry and often cold Mexican winter feeding only sporadically, if at all. Because the corn stunt spiroplasma (CSS) apparently overwinters inD. maidis, we investigated its effect on the ability ofD. maidisto survive these winter conditions (low temperatures and loss of host plants). We used two types of tests: exposing leafhoppers to either −5°C over 24 h or to less severe low temperatures (10 to 20°C) and starvation over several months. We used leafhoppers reared under fall conditions, previously shown to be more cold hardy, and varied food and water sources to simulate loss of host plants. We compared survival of males and females from laboratory colonies established from three field populations in Mexico. Our results do not support previous findings that CSS infection protectsD. maidisfrom below zero temperatures. However, CSS improved survival at 10 to 20°C whenD. maidiswas provided only moist sand or maintained on oats (a feeding host), and preferentially benefitted females; for example, over all treatments, survival of infected individuals was 1.1 times that of un infected leafhoppers, but on moist sand, survival of CSS infected females averaged 2.2 times that of uninfected females. We conclude that, under certain conditions, CSS infection can benefit its vector and may play an important role inD. maidisoverwintering strategies.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.634

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Feeding behavior of fourth- and sixth-instar spruce budworm,Choristoneura fumiferanaClem., toward aqueous extracts of balsam fir (Abies balsamea(L.) Mill.) foliage from terminal and lateral shoots of young and old trees is described. Fourth instars prefer extracts from terminal shoots of young and old trees. This feeding preference is correlated with the content of N in the foliage and the feeding rate is correlated with the N/tannin ratio. Sixth instars show a strong preference for extracts from lateral shoots of young trees. Their feeding preference is correlated with the sucrose content of the foliage, whereas their feeding rate is correlated with the glucose content. Age-related variation in bud worm larval feeding preference may be an important evolutionary adaptation for the spruce budworm, enabling it to respond positively to naturally occurring seasonal changes in the nutritional quality of its host plant and to chemical changes induced by defoliation.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.645

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The influence of an intercropped agroecosystem of oilseed rape, canola-type (Brassica napusL.), and field pea (Pisum sativumL.) on the population level of the flea beetle,Phyllotreta cruciferae(Goeze), was evaluated for 3 yr in east-central North Dakota. Treatments included two monocultures of oilseed rape (8 kg/ha of live seed) and field pea (200 kg/ha of live seed) and three intercropped mixtures of field pea to oilseed rape (150:2, 100:4, and 50:6 [kg/ha]). Flea beetle counts per 0.5 m2were highest in the oilseed rape monoculture in all 3 yr of the study but significantly higher from the other treatments in only one year. The sex ratio ofP. cruciferaeadults collected was not influenced by the treatments. The land equivalent ratios (LER = [intercropped yield for pea/monoculture yield for pea] + [intercropped yield for rape/monoculture yield for rape]) for the intercrop treatments did not exceed 1.0, indicating that the intercrops selected were not as efficient for yield as the monocultures. This intercrop system was not effective in reducing flea beetle loads on a per-plant basis, nor was there a yield advantage from this intercrop system.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.654

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Head capsules of 579 individuals from 28 different populations of gypsy moth,Lymantria dispar(L.), were reliably classified with an analysis of their color spectrum. Based on 26 variables, derived from ≈17 million color combinations of red, green, and blue, a set of numeric characteristics permitted discrimination between gypsy moth populations from the former Soviet Union, the northeastern United States, and the laboratory. Discriminant analysis of color spectra also differentiated among laboratory families reared on the same diet as well as instars within the same family. The 26 variables, which were derived from a series of discriminant analyses and tested on head capsules from populations from Japan, China, Yugoslavia, and Maryland, provided separation as well as a high level of correct classification. This procedure may be useful when head capsule or other spectral data are used in studies of biocontrol, behavior, and population dynamics.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.659

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Preliminary field screening of 50 rice lines of various origin in 1990 for resistance to rice water weevil,Lissorhoptrus oryzophilusKuschel, yielded several lines with potential for resistance. These lines were divided into two groups and evaluated in the field in 1991 and 1992. One group was evaluated specifically for tolerance and the other was tested for antibiosis or antixenosis or both. Significant differences were found among the lines tested for tolerance using rice water weevil larval population levels, root damage ratings, plant height, and grain yield as indicators. The comparison of untreated and treated plots indicated that lines AL6029, LA2218, TX22041, URN199 and URN200 showed tolerance to the rice water weevil. Tolerance was expressed in part as the ability of the lines to recover from root damage and produce high grain yield while supporting a high rice water weevil larval population. Lines TX12685 and TX13079 in the antixenosis test showed moderate levels of resistance to the rice water weevil, with significantly lower larval populations than the susceptible standard ‘Mars’.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.665

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Nocturnal aerial insect flight activities between 30 and 900 m above ground level were monitored with 3-cm scanning radar during the spring, summer, and fall seasons of 1988 and 1989 in the Brazos River Valley of Burleson County near College Station, TX. Surface meteorological parameters were measured continuously with weather station instrumentation, and radiosondes carried aloft by weather balloons were used to measure upper-air temperatures and wind conditions. Aerial volume density patterns and flight behaviors observed with radar varied nightly because of the many biological and meteorological variables involved, but certain seasonal characteristics of insect flight behavior became apparent during the course of the research. Nightly local dispersal flights at dusk were the norm, especially during the summer. Large numbers of insects were typically airborne for 1 to 2 h beginning about one-half hour after sunset with some of them reaching altitudes of 800 m or more where wind speeds were typically greater than 30 km/h. Several apparent long-range migration-type insect movement events were observed in which insects were concentrated in layers in high-speed, low-level wind jets that were apparently associated with nocturnal upper-air temperature inversions. Migration-type movement of insects tended to be south to north in the spring and early summer and north to south in the fall.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.676

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The activity of carabid beetles and predation pressure of ground-dwelling predators were investigated in four crop types, barley (Hordeum vulgareL.), faba bean (Vicia fabaL.), barley-pea (Pisum sativumL.) intercrop and fescue (Festuca rubraL.). Pitfall captures of carabids and disappearance rate of experimentally placed fly pupae were similar across the intercrop of peas and barley and monocultures of faba bean and barley, but pupal disappearance was lower in plots of fescue grass than in the crops. In habitat choice experiments, the intercrop attracted significantly more individuals ofPterostichus melanariusIlliger than did the three monocultures. Our results show that carabids can be affected by vegetation structure associated with differences in agronomic practice and that such effects have potential implication for rates of predation in agricultural systems.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.684

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The sweetpotato whitefly,Bemisia tabaci(Gennadius), is a major agricultural pest, causing over 200 million damage to cotton alone in the United States in 1992. To understand sweetpotato whitefly feeding behavior, we examined the effects of phosphorus nutrition and leaf age on sweetpotato whitefly host selection. Cotton (Gossypium hirsutumL.) seedlings grown either hydroponically in growth chambers or in sand culture in the greenhouse were exposed to sweetpotato whitefly adults when two fully expanded true leaves were present. Phosphorus deficiency reduced oviposition on true leaves by 40% in the growth chamber, and by 38% on the youngest expanded leaf in the greenhouse, but had no effect on oviposition on cotyledons in either environment. When individual leaves from the greenhouse were analyzed, host acceptance was significantly correlated with low leaf sucrose concentration, but appeared to be unrelated to amino acid concentration or amino acid:sucrose ratio. This suggests that host selection was based on minimizing osmotic stress to the insect rather than on maximizing amino acid ingestion.

ISSN:0046-225X    

DOI:10.1093/ee/23.3.693

出版商:Oxford University Press    

年代:1994

数据来源: OUP