摘要:

To determine if baldcypress,Taxodium distichum(L.) Richard, could be a “most suitable host” for gypsy moth,Lymantria dispar(L.), we fed laboratory-reared larvae white oak,Quercus albaL. (a “most preferred host” species), baldcypress, or a mixed diet of baldcypress and white oak, and monitored survival, development, and fecundity for 2 developmental years. Criteria for most suitable host were>80% survival of 1st instars, development to pupation in350 full sized ova. Our 1990 and 1992 laboratory studies indicate that baldcypress generally met these critCl; a, and we consider baldcypress a most suitable host for gypsy moth. In 1990 and 1992, respectively, 69 and 83% of 1st instars survived after being reared on baldcypress, compared with 77 and 74% on white oak and 82 and 87% on mixed diet. In 1990 and 1992 61 % of larvae fed baldcypress completed larval development and pupated, as opposed to 7.3 and 56% on white oak and 80 and 83% on mixed diet. For 1990, mean days to pupation and adult emergence, respectively, were 50 and 63 d for baldcypress, 47 and 56 d for white oak, and 47 and 59 d for mixed diet. Mean days to pupation and adult emergence for 1992, respectively, were 48 and 61 d for baldcypress, 46 and 60 d on white oak, and 48 and 61 d on mixed diet. The percentage of pupae that emerged as adults in 1990 and 1992, respectively, were 74 and 98% on baldcypress, 96 and 100% on white oak, and 95 and 99% on mixed diet. Mean female pupal weights for 1992 were 1,100 mg (baldcypress), 1,350 mg (white oak) and 1,440 mg (mixed diet). Mean numbers of ova produced for 1990 and 1992, respectively, were 475 and 451 for baldcypress, 453 and 456 for white oak, and 508 and 519 for mixed diet.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1069

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The fungal pathogen,Discula destructivaRedlin, has been responsible for the decline or death, or both, of flowering dogwood,Cornus floridaL., in the eastern United States. Our research addressed the role of a selected insect in transportation and dissemination ofD. destructiva. Densities of conidia on adults of our model insect, the convergent lady beetle,Hippodamia convergensGuérin-Ménevile, were quantified using scanning electron microscopy. Significantly more conidia were attached to the ventral body surface than to the dorsal surface. Also, conidia were deposited around trichomes of dogwood leaves exposed to infested convergent lady beetles. Our data demonstrate that our model, the convergent lady beetle, is capable of transporting conidia ofD. destrutctiva. Because conidia may remain viable for 16 d, insects may play an important role in the epidemiology of dogwood anthracnose.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1075

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Corn earworm,Helicoverpa(=Heliothis)zea(Boddie), and tobacco budworm,H. virescens(F.), arc polyphagous, multivoltine insect pests that feed on numerous cultivated and wild bost plants. In eastern Tennessee during 1990 and 1991, larvae ofH. zeawere collected from 34 species of wild host plants in 11 families, and huvae ofH. virescenswere collected from 20 species in 9 families. One or the other or both species were found on a total of 39 species of wild hosts in 11 families. Early-season (june through July) wild host plants of both insect species included common mallow.Malva neglectaWallroth, black medic,Medicago lupulinaL., and crown vetch,Coronilla variaL. Hophornbeam copperleaf,Acalypha ostryaefoliaRidell, hairy galinsoga,Galinsoga cilliata(Rafinesque Blake, and crown vetch may be new host-plant records forH. zeaandH. virescens. Dovefoot gerauium,Geraniium molleL., may represent a new host-plant record forH. zea. The diversity of the wild hostplant complex ofH. zeaandH. virescensin eastern Tennessee reflects the variety of suitable flora in this region. This host-plant diversity coupled with the patchy distribution of cropland within the regional agroecosystems may combine to prevent populations ofH. zeaandH. virescensfrom reaching the outbreak levels expelienced in other regions of the United States.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1080

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

To determine if the phenology ofEmpoasca fabae(Harris) includes reproductive diapause, the progeny of females collected in Louisiana were reared under various conditions of photoperiod and temperature. Adults were paired, and the oviposition of each female was recorded for 40 d at 4-d intervals. Short day lengths resulted in a lower proportion ofE. fabaeovipositing, a longer preoviposition period, and a decreased rate of oviposition. These responses constitute evidence for the induction of reproductive diapause. To determine whether reproductive diapause is expressed in northern populations in the field, 4th and 5th instars from New York state were reared at intervals through summer and fall. and tested for response to photoperiod. The proportion ofE. fabaefemales becoming reproductively mature decreased as the season progressed. Less than 50% of field-reared females became gravid after mid-July. In the laboratory, reproductive maturation in field-reared females was retarded by short day lengths, but not by long day lengths. The induction of reproductive diapause in late summer supports the hypothesis thatE. fabaeengages in a diapause-mediated southward migration to its overwintering area.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1086

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

It has been hypothesized thatEmpoasca fabae(Harris) lacks specific adaptations for surviving temperate zone winters, but recent findings suggest otherwise. Observations indicating thatE. fabaepasses winter in reproductive diapause motivated a reevaluation ofE. fabaephenology. Ovarian dissections revealed that no overwintering females collected from Louisiana in mid-January 1991 had mature oocytes, whereas 65% of females collected in late February did. Field-collected females were held in the laboratory under 4 different combinations of photoperiod and temperature. Among females collected in mid-January, short day lengths and low temperatures helped maintain a nonreproductive state. Most females collected in late February began laying eggs within 3 wk, regardless of photoperiod or temperature, indicating that diapause was broken in field populations between mid-January and late February in 1991. OverwinteringE. fabaewere found on a variety of native evergreen plants, especially pines, over an area roughly approximated by the southern pine region, and also on a variety of primarily exotic herbaceous legumes in areas near the Gulf Coast. Repeated surveys of various sites in 1992 indicated that reproductive maturation of overwintering females occurred in mid- to late February, as the population shifted from evergreens to legumes and celtain deciduous trees, on which spring generations were initiated. The results of this study, viewed in conjunction with previous works, suggest thatE. fabaeis well adapted to native conditions in temperate North America, and that its phenology includes a return migration to overwintering areas.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1096

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Various populations presumed to be potato leafhopper,Empoasca fabae(Harris), were collected from various host plants and locations, and then e1ectrophoretically assayed for 12 enzyme loci. There was no evidence of genetic differentiation between populations. Small populations ofE. kraemeri,E. erigeron, andE.compareperlongawere assayed.E. kraemeriis a cryptic member of the fabae complex, and may occur together withE. fabae. Diagnostic alleles were found to distinguish betweenE. fabaeand the 3 otherEmpoascaspecies.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1109

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Development time of the potato leafhopper,Empoasca fabae(Harris), was determined in the laboratory under conditions simulating spring in Louisiana. Development time differences between 4 leguminous host plants were statistically significant but small. All published temperature-dependant models ofE. fabaedevelopment predicted mean development time within 10% of the true overall mean. Field studies ofE. fabaedevelopment in the spring in Louisiana revealed significant but small development time differences between 2 leguminous hosts. Model predictions were generally within 10% of the true mean development time. This result was robust for 5 different sources of temperature data. Any of 3 published models ofE. fabaedevelopment are recommended for use with maximum and minimum temperature data from standard weather stations for predicting mean development time of migrant source populations. It is recommended that host-plant effects not be included.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1115

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Single-night flight performances of 256 feral com earworm males,Helicoverpa zea(Boddie), were measured with a 32-channel, computer-monitored flight-mill system to evaluate their potential and propensity for engaging in long-distance, migratory-type flight. Test moths were males of mixed age that were selected randomly from daily catches in pheromone-baited traps located adjacent to fields of silking corn,Zea mays(L.), in Burleson County near College Station, TX, during the period of 16 and 30 June 1992. Flight was observed in 96% (n = 256) of the moths tested; however, because of mortality and other factors, only 52% (134) remained capable of flight throughout the 9.75-h simulated scotophase period. The 134 moths averaged Hying a total distance of 32.53 km in 17 separate Hights during 5.61 h of total flight time which included an average maximum-duration sustained single flight of 18.8 km of 2.98 h duration. Thus, the feralH. zeamales demonstrated a high potential for long distance flight. Other observed characteristics of moth behavior and flight performance are discussed, and the flight-mill system is described.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1122

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We studied the movement of colonies of the black imported fire ant,Solenopsis riehteriForel, in its native land, Buenos Aires province, Argentina. We established 6 field plots and monthly monitored the number of abandoned and new mounds for 2 yr. We compared the movement of all colonies with the movement of colonies infected with the microsporidiumThelohania solenopsaeKnell, Allen&Hazard. We estimated the distance of colony movement and recorded the duration of the colonies remaining in the same place.S. richtericolonies moved their mounds very often. The mean percentage of abandoned and new mounds per monitoring date was 36 and 30% of all active mounds, respectively. The pathogenT. solenopsaedid not have any effect on colony movement. The mean estimated distance of displacement was 3.7 m and the mean duration of the colonies in the same place was 3.1 mo. Rainfall stimulated colony movement in Argentina.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1131

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Field experiments were established in 1993 and 1994 to investigate population levels and parasitism of silverleaf whitefly,Bemisia argentifoliiBellows&Perring, on 3 nearisolines of soybean,Glycine maxL., that varied in hairiness, and on 1 cultivar of peanut,Arachis hypogaeaL. The original intent was to determine whether soybean could be used as a trap crop to reduce whitefly infestation in peanut. In 1993, we found that whiteflies preferred soybean to the extent that they laid few eggs on peanut in the trap crop experiment. Substantially greater populations of immature whiteflies occurred in pubescent and hirsute soybean than in either glabrous soybean or peanut. In 1994, only pubescent soybean supported substantially greater number of whiteflies than glabrous soybean, however, all soybean genotypes supported more whiteflies than peanut. In 1993, whiteflies were less often parasitized on hirsute soybean than on peanut or on the other soybean genotypes. In 1994, however, parasitism differed significantly among the 4 plant types on only 2 dates. In both years, parasitoid species were distributed differently on the 4 plant types.Encarsia nigricephalaDozier andEncarsia transvenaTimberlake more commonly parasitized whitefly on peanut and on glabrous soybean than on the hairy soybean genotypes. Conversely,Encarsia pergandiellaHoward andEretmocerusnr.californicusHoward more often parasitized whitefly on the hairy soybean genotypes.

ISSN:1754-5692    

DOI:10.1093/ee/24.5.1135

出版商:Oxford University Press    

年代:1995

数据来源: OUP