摘要:

Trichome density and erectness, plant height, plant canopy closure, and epicuticular lipid composition were measured from 14 soybean genotypes at 2 locations in Tift County, Georgia, for potential whitefly resistance mechanisms. Differences were noted in the number of trichomes per 300–mm2leaf area, plant heights, and canopy closure indices for the 14 soybean entries, but these differences showed no correlation to 1993 and 1994 infestation levels ofBemisia argentifoliiBellows&Perring andTrialeurodes abutilonea(Haldeman). However, differences in trichome erectness ratings corresponded to differences in whitefly populations during both seasons, particularly in 1994 when overall population densities were higher. ‘N88–9l’, ‘Cook’, and ‘Perrin’ had lower seasonal mean densities of whiteflies in 1993 and 1994 than several of the other entries. These entries also had higher erectness ratings (trichomes flat on leaf surface) than the entries with higher whitefly populations. ‘N89–1’ had lower erectness ratings (trichomes erect) and higher whitefly populations than most other entries in both 1993 and 1994. Analysis of the epicuticular lipid composition of 10 soybean genotypes detected differences among the entries of levels for n–hentriacontane, a–amyrin, 13– amyrin, and lupeol (triterpenol). These differences were not correlated to whitefly population densities for any of the chemical constituents. However, entries with low levels of lupeol (below 5 μg/cm2)tended to have higher whitefly populations.B. argentifoliiwas the predominant whitefly species observed at this test site. Over 85% of the immatures observed on the leaf surface and over 90% of the adult whiteflies captured on yellow sticky cards wereB. argentifolii, whereas low numbers ofT. abutiloneawere observed.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1381

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Several modifications of a plastic dry trap baited with synthetic lures (ammonium acetate and putrescine) were field tested in Guatemala for capture of the Mediterranean fruit fly,Ceratitis capitata(Wiedemann), and the Mexican fruit fly,Anastrepha ludens(Loew). The cylindrical plastic dry trap has 3 holes for release of internally placed chemical lure as well as for insect access into the trap, and a painted band that provides a visual cue. Fruit flies entering the trap move to internally placed toxicant–sugar panels, causing insect death after they feed. Visual cue modifications in traps painted green or orange included comparisons between shiny or dull trap exteriors and among a range of widths of the painted band on the trap body (3–15 cm wide). Chemical cue modifications included 3 versus 6 access holes in the body of the cylindrical dry trap and tests of 2 doses of a new putrescine formulation. The greatest amount of discrimination among the tested modifications was demonstrated by femaleC. capitata. The highest capture of femaleC. capitatawas in green 3–hole traps with dull exteriors and with visual cues 12–15 cm wide. Variation in the width of the visual cue and in the number of access holes had less effect on capture of maleC. capitatathan on females, but capture of males was the lowest in orange traps with shiny exteriors. Capture of femaleA. ludenswas relatively unaffected by the modifications tested, although highest capture was obtained with the green visual cue of 3–7.5 em and the orange visual cue of 7.5–12 cm. MaleA. ludensresponse was similar to that observed in females, although the capture of males among the modifications tested was more variable. There were interactions between visual cues associated with the trap body and the dose of putrescine, thus optimal dose of putrescine may vary with visual cue used in the trap design. Results from this study indicate that modifications in the plastic dry trap can be used to improve the capture of femaleC. capitataand to develop more cost–effective dry traps for field use against pest Tephritidae.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1387

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Emission characteristics of 3 sex pheromone components, (E,E)–8, 10–dodecadien– 1–01[codlemone], 1–dodecanol, and I–tetradecanol, of codling moth,Cydia pomonella(L.), were determined from a polyethylene tube dispenser. A model predicting emission rate of codlemone as a function of accumulated degree hours and temperature was developed. The effectiveness of different blends and estimated emission rates of codlemone at dusk in disrupting sexual communication of codling moth were evaluated in field tests in apple (Malus X domestica[Borkham]) during 1991–1992. In all field tests, virgin female–baited traps and releases of marked male moths were used. Traps were placed at 3 heights in the canopy in 9 orchards treated with 1,000 polyethylene tube dispensers per hectare and a single untreated orchard. Trap height significantly affected moth catch in both the pheromone–treated and untreated orchards. The difference in moth catches between pheromone–treated and the untreated orchard with respect to the estimated codlemone emission rate at dusk was substantial for each height, and tile slopes did not differ among heights. A significant negative regression was found for moth catch and the estimated codlemone emission rate from fibre dispensers aged in the field 0–120 d in small plots (0.1 hal. No difference in moth catch was found for plots treated with Celcon hollow fiber dispensers emitting codlemone versus a 3–component blend. Emission rate was a significant factor affecting moth catch. Problems associated with using these data to establish a minimum effective pheromone emission rate for disruption of codling moth are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1396

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We present a technique for determining dates of alfalfa weevil,Hypera postica(Gyllenhal), egg eclosion by correlating degree–day accumulations with calendar dates. This technique uses historical climate data from various locations to calculate the median date a degree–day accumulation has been reached. ClimProb 3.1, a computer software program and weather database, was used to assess these correlations. We used 165 locations in 12 midwestern states for the analysis. Sixty years (1931–1990) of continuous daily climate data (maximum temperature, minimum temperature, and liquid precipitation) were used for each location. We began degree–day accumulations on 1 January of each year and used a minimum developmental threshold of 8.9°C (48°F). Degree–day accumulations were determined using a sine–wave method. The relationship between the date when the accumulated degree–days reached a threshold and the location (expressed as degrees north latitude) was quadratic from 36° N to 48° N. The technique gives approximate dates when egg hatch is likely to occur throughout the north central United States, and these dates can be used to augment existing decision criteria for initiating sampling programs for alfalfa weevil. This technique can be used for other pest management programs that depend on estimating pest development.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1404

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Field studies were conducted in 1993 to investigate a possible sexual dimorphism in the elytra coloration pattern of western com rootworm,Diabrotica virgifera virgiferaLeConte, adults, and to compare the sex ratio of adults captured on 2 types (Olson and Pherocon AM) of commercial yellow sticky traps with those obtained by aspiration. Striped and solid variationsin elytra pattern were found in both sexes. Of the western corn rootworm adults that exhibited the solid elytra pattern,>99% captured on yellow stickytraps and 97% collected by aspiration were male. In contrast, of those adults which exhibited the striped elytra pattern, 79% captured on yellow stickytraps and 42% collected by aspiration were male. Sex ratio of adults varied significantly over time and among sampling methods. Sticky traps captured a significantly greater proportion of males compared with aspiration. No significant difference in sex ratio was found between the 2 types of sticky traps; however,the Olson trap captured significantly more com rootworm adults overall than the modified Pherocon AM trap.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1408

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We monitored prevalence ofNeozygites fresenii(Nowakowski) Batko in populations of cotton aphids,Aphis gossypiiGlover, during a 3–yr period and used these data to develop sampling strategies for predicting aphid population decline caused by disease. Aphid populations began to decline when average fungal prevalence (percentage of fungus–killed aphids) reached =15%. Populations declined to low levels 5–16 d later. Declines were more rapid in fields with higher initial densities of aphids. Fungus–killed aphids were detectable up to 10 d before prevalences reached =15%. Detection at this early stage required (theoretically) the examination of 70–150 leaves per field (95% probability of detection). However, a sample size of only 4–5 leaves was required for detection after prevalence reached 4%, which would be expected to occur =4 d before initial decline of aphid populations. With microscopic examination of 100 aphids per leaf, detection of fungus–infected aphids (95% probability) required between 9 and 17 leaf samples 10 d before decline of aphid populations, but only 1 sample was required 4 d before decline of aphid populations. During early stages of epizootics (prevalences<15%), fungal prevalences were greater on leaves 6 nodes below terminals, compared with leaves at the 1st or 2nd positions below terminals. During this time, fungal prevalences were correlated in subsamples collected 2 m apart. In samples collected 100 m apart during the very early stages of epizootics (prevalences<1%), distributions of infected aphids were clumped in 1 of 3 sample fields. These results underscore the importance of representative sampling of cotton fields if the goal is early prediction of epizootics.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1414

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Ninety–sixspecies and varieties of seeds in 28 families were presented to laboratory colonies ofSolenopsis invictaBuren. Small seeds were moved and subsequently damaged more often than large seeds. Although generally more resistant to damage, some species with large seeds such as com, Zea mays L., were susceptible toS. invictadamage. Seed coats protected some seed species from ant damage. Presence of repellent and attractant surface chemical swas also demonstrated for some seeds. Although chemicals could be extracted from seeds that could be considered attractive, some seeds appeared to be protected fromS. invictapredation by repellents (predation means the seed is damaged so extensively that it can no longer germinate). Many species of seeds were susceptible to some degree ofS. invictapredation, and most were transported to new locations. We also soaked seeds, which in general increased their susceptibility to predation, although seed removal was reduced. Seeds that were beginning to germinate were difficult to characterize: some germinated seeds were more susceptible to predation, but other germinated seeds were less susceptible to predation. Of resistant and susceptible seeds, Fabaceae seeds were most resistant and Labiatae seeds were most susceptible toS. invictamovement and damage. Seeds may play an important role as a food resource forS. invicta, and, as a result,S. invictamay be serious seed predators and competitors of animals for which seeds represent an important resource.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1422

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Grasshopper and plant community relationships in southern Idaho were examined within a life–history context. Plant species composition (by weight) and density and species composition of grasshoppers were estimated at 52 sites in south–central Idaho, representing a range of plant communities from native sagebrush–bunchgrass to exotic annual grasslands.The plant community at each site was evaluated using the Grime triangular model of plant life–history strategies,which consists of 3 axes representing adaptations to competition, stress, and disturbance. Four attributes were measured for the 20 most common grasshopper species: mean density, habitat breadth, average instar in June, and diet breadth. Grasshopper density, habitat breadth, and diet breadth were correlated positively with site scores on the disturbance axis of the Grime life–history model and were correlated negatively with site scores on the competition and stress axes. Results suggest that characterization of grasshopper and plant community life–history strategies provides useful insights for understanding the dynamics of grasshopper assemblages from different habitats.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1432

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Three species of arboreal nesting termites common in New Guinean coconut plantations:Microcerotermes biroi(Desneux),Nasutitermes princeps(Desneux), andNasutitermes novarumhebridarum(N. and K. Holmgren), are in competition with each other. This work evaluated the influence of environmental factors on this community. We compared the arboreal nesting termite distribution, abundance, and colony size in the following 3 types of coconut plantation: (1) open plantations with tall trees (=25 m) at low density (≤100 trees per hectare); (2) standard plantations with medium size trees (=13 m) at standard density (100–180 trees per hectare); (3) dense plantations (180–300 trees per hectare) with medium size or mixed size trees (13–25 m). The overall proportion of coconut trees occupied byarboreal termites increased from 25% in open plantations to 56% in standard or dense plantations.M. biroiwas less abundant in open plantations than in standard or dense ones, whereasN. princepswas scarcest in standard plantations.N. novarumhebridarumoccupied =2% of the trees in all plantation types, but showed a clear preference for dead trees. Nest volumes of all species and colony territories were larger in dense plantations, especially forN. princeps. Data on nest thermoregulation suggest thatM. biroiis the most affected by sun exposure, which could constitute a limiting factor in open plantations.N. princepsincipient colonies would be particularly hindered by competition with first established colonies ofM. biroiin standard plantations. Large territories ofN. princepsin dense plantations suggest that this species is especially favored by high tree densities, allowing easy colony expansion by galleries or satellite nests and reproduction by budding. We propose that arboreal termite community structure is mainly shaped by microclimatic conditions and food availability in open plantations, and by interspecific competition in denser habitats, although the incidence of other factors, such as predation or intraspecific competition, remains to be studied.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1442

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Thirty forested plots throughout Connecticut were established to determine the associationof forest site conditions with population sizes of common ants (Hymenoptera: Formicidae).The plot characteristics investigated were plot slope, elevation,longitude,latitude, basal area of trees and number of understory stems of species associated with moist conditions, and total length of intersection of rocks along 4 plot transects.Two plot characteristics were consistently related to ant abundance: plot latitude and basal area of trees that prefer mesic or wet sites. Ant numbers were less at high latitudes and in moister sites. Implications of these results for improving biological control by ants are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.6.1453

出版商:Oxford University Press    

年代:1995

数据来源: OUP