摘要:

Biotype E greenbugs,Schizaphis graminum(Rondani), were reared on corn,Zea maysL., to assess their ability to develop, reproduce, and survive on this host. Four corn germ plasm accessions (Antigua, OH-45, AP-670, and 2570) were studied along with a susceptible grain sorghum,Sorghum bicolor(L.) Moench, (NC + 630x) and a resistant sorghum (PI 264453) as controls. Corn-reared and sorghum-reared greenbugs were tested to evaluate the effect of host history on performance. Daily mortality and fecundity schedules were measured and net reproductive rate, intrinsic rate of population increase, finite rate of increase, and population doubling time were calculated. Plant entry had a significant effect on development time for the first two instars but not the second two, which may be because of physiological adaptation to the novel hosts. All life-history measures except generation time indicated greater potential for greenbug population growth on sorghum than on corn. However, greenbugs still had sufficiently high population growth on corn to indicate that corn was a good host. Better performance on both sorghums and Antigua corn compared with the other corn entries suggested the possible involvement of the MBOA–DIMBOA complex in resistance to greenbugs. Longevity was greater and population doubling time was shorter for corn-reared than for sorghum-reared greenbugs. Host history also interacted with plant entry such that corn-reared greenbugs were more fecund on corn than sorghum-reared ones, whereas the opposite was true on sorghum. Assessment of these data indicates that greenbugs have a potential to adapt to corn as a true host and develop a biotype injurious to corn.

DOI:10.1093/ee/19.4.949

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Marked Japanese beetles,Popillia japonicaNewman, were released and recaptured in experimental plots to test the effect of contrasting types of strip-cropped soybean agroecosystems on beetle dispersal. Experimental treatments were soybean monoculture, soybean strip-cropped with dwarf sorghum (≍1 m tall), and soybean strip-cropped with tall sorghum (>2 m tall). Three hundred marked Japanese beetles were released in the center soybean strip of each treatment in small (0.11 ha) and large (0.45 ha) experimental plots. Beetles remained longer in the center soybean strip in the strip-cropped bicultures than in the monocultures indicating that the sorghum strips inhibited their movement. Dispersal rates were similar in dwarf and tall sorghum treatments despite differences in plant height. Significantly more marked beetles in the small plots, however, emigrated from the ends of the center soybean strip in the tall sorghum biculture than in the other two treatments indicating that tall sorghum oriented beetles to move parallel to intercropped strips. Japanese beetles responded to the sharp boundaries between host and nonhost habitat patches, as has been previously reported for host specific herbivorous insects. Results suggest that strip-cropping can affect the movement of polyphagous herbivorous insects and provide benefits for pest management in large-scale agroecosystems.

DOI:10.1093/ee/19.4.955

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The dispersal of adultAnopheles quadrimaculatusSay was evaluated by techniques involving wild capture, fluorescent marking, release, and recapture of adult mosquitoes from a naturally occurring population in the rice-growing region of Arkansas. Males and females dispersed mean distances of 1.05 and 1.84 km, respectively, from the release point over a 2-d period. The maximum time from release to recapture was 13 d. A recommendation for insecticidal treatment of at least 3.4 km2surrounding any targeted source for this mosquito was made based on results of the study.

DOI:10.1093/ee/19.4.961

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Oviposition preferences of the southern corn rootworm,Diabrotica undecimpunctata howardiBarber, were investigated in greenhouse experiments where abiotic and biotic parameters were manipulated. Southern corn rootworm oviposition distance from corn seedlings was quantified. Four soil moistures, four soil textures, and the presence of weeds were examined in caged greenhouse experiments for their effect on southern corn rootworm oviposition preference. Additional experiments were conducted to elucidate southern corn rootworm oviposition preference for corn seedlings in the presence of broadleaf weeds, grass weeds, a wheat straw cover, or bare soil in large-cage experiments in the greenhouse. Southern corn rootworm adults oviposited>90% of their eggs within 3 cm of a corn stem with<1% oviposited 10–15 cm from the plant. Soil moisture and texture significantly affected oviposition preference. Moist or wet soil and dark soils (moderately high in organic matter and clay) were preferred for oviposition. Significant interactions occurred between these two variables. The presence of weeds significantly increased the number of eggs oviposited and influenced the oviposition preference for particular soil moistures and textures. Southern corn rootworm adults preferred to feed on and oviposit in areas that contained broadleaf weeds compared with grass weeds, wheatstraw, or bare soil. The presence of a wheatstraw cover was significantly (P<0.05) preferred to bare soil. We discuss how this study elucidates a number of seemingly contradictory field observations of southern corn rootworm infestations.

DOI:10.1093/ee/19.4.966

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Life history characteristics of the goldenrod gallmaker,Eurosta solidaginisFitch (Diptera: Tephritidae), were compared between individuals using separate host species. Infestation rate, gall size, gallmaker larval weight, gallmaker mortality, and parasitoid/predator attack frequencies were examined. Galls fromSolidago altissimaL. (Compositae) averaged 10% less in diameter than those ofS. giganteaAit. Discordantly, the larval weights of theS. altissimalarvae were 26% greater. Gallmaker mortality was approximately equal, although the underlying causes differed. Some of these differences can be explained by difference in gall size. TheS. altissimagalls, with their smaller mean size, were more vulnerable to attack by the parasitoid wasp,Eurytoma giganteaWalsh (Hymenoptera: Eurytomidae). On the other hand,S. giganteagalls, with their greater mean size, were more vulnerable to attack by birds. Early larval death of the gallmaker was greater onS. gigantea. Although survivorship did not differ on the two host plants, the larger size of larval fromS. altissimawould suggest that females emerging from this host would have greater fecundity. AlthoughS. altissimaappears to be the better host,S. giganteawas more heavily infested. The seemingly maladaptive lack of correlation between infestation and performance could be explained if the insects from the two plant species represent two host races.

DOI:10.1093/ee/19.4.972

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Seven species of insects including ground beetles, tiger beetles, earwigs, and the red imported fire ant,Solenopsis invictaBuren, were identified in laboratory feeding trials as pupal predators of velvetbean caterpillar,Anticarsia gemmatalisHübner. The survivorship and predation of velvetbean caterpillar pupae were studied in soybean fields in Louisiana. Two descriptive categories of predatory feeding action were identified, “partial” and “complete”. Predation was the principal mortality factor, accounting for 52.5 to 95.2% mortality in plots with fire ants. The red imported fire ant was a primary predator, accounting for 77.5 to 96.5% of total predator mortality for pupae under the soil surface in plots with fire ants. Our studies also indicated that the red imported fire ant seemed to reduce other ground-dwelling pupal predators of velvetbean caterpillar.

DOI:10.1093/ee/19.4.978

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

This study examined effects of nonhost plant neighbors on population densities and parasitism rates of the diamondback moth,Plutella xylostella(L.), in Hawaii. Monospecific cabbage plots had greater larval densities, lower numbers of larvae parasitized byCotesia plutellae(Kurdjumov), and lower percentage of parasitism compared with plots of cabbage interplanted with tomato. Larval densities were affected directly by tomato neighbors rather than by indirect changes in host plant size or quality. However, tomato neighbors did not significantly influence densities of pupae, emerging adults, or total leaf herbivory. Laboratory experiments showed that ovipositing females did not discriminate between cabbage grown alone versus cabbage grown with tomato. These results suggest that tomato neighbors affect long-range host finding or early egg-larval survival, or both, in the field as well as parasitism rates.

DOI:10.1093/ee/19.4.987

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A trapping study using a Latin-cube design was conducted in an apple variety block in 1987 to determine the effect of microorganisms on the attraction of green June beetlesCotinis nitida(L.) (Coleoptera: Scarabaeidae) to fruit. Baffle and funnel traps baited with male beetles fed nystatin-treated peach puree diet caught significantly fewer beetles than beetles fed untreated peach puree, streptomycin-penicillin-treated puree, streptomycin-penicillin-nystatin-treated puree, 20% untreated glucose diet, and beetles caged with diet but prevented from feeding (P<0.05). In 1988 a study was conducted in a vineyard using the same traps and a similar experimental design. Traps baited with beetles fed nystatin-treated diet caught significantly fewer beetles than traps baited with beetles fed untreated puree and beetles caged with untreated puree but prevented from feeding. Traps baited with beetles fed untreated puree again caught significantly more beetles than all other treatments (P<0.05). These results suggest that yeasts contained in diet, and possibly in beetle digestive tracts, contributed significantly to the production of volatiles, which induce beetle aggregations on fruit.

DOI:10.1093/ee/19.4.995

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Time-specific life tables were developed forAcyrthosiphon kondoiShinji in Oklahoma during growth of the first alfalfa crop in 1985 and 1986. In each year, population densities increased rapidly (from200 aphids per stem) during a 2–3-wk period between early March and May. In the first interval of population growth each year, the observed rates were equivalent to the intrinsic rate of increase determined in laboratory studies. Although alatae were produced throughout the period of population growth, a rapid increase in the prevalence of this morph resulted in proportions of winged adults exceeding 90% just before population decline. A rapid decrease in numbers ofA. kondoifrom the peak densities occurred due to emigration of alatae and the resulting decrease in nymphal production. Although predaceous insects (primarilyHippodamia convergensGuerin-Meneville) were present in moderate numbers (up to 0.2 individuals per stem), there was little evidence of limitation imposed on the growth rates of the aphid population. We observed no parasitized or diseased aphids and it appeared that natural controls were not effective in slowing the rapid growth of populations and preventing outbreaks during our study. Except for emigration of alatae, no factors were identified that reduced population densities by detectable amounts.

DOI:10.1093/ee/19.4.1001

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Densities of adultAulonium ruficorneOlivier were significantly higher when the beetle prey,Orthotomicus erosus(Wollaston), were in the first two instars. Under controlled conditions, adult longevity was 33.5 d. FemaleA. ruficornewere more abundant during bark beetle colonization and, later, during the bark beetles' larval stage. However, males outnumbered females during bark beetle oviposition. Eggs were laid under bark scales, in crevices, and in bark beetle frass. The egg distribution was mainly a function of the bark scale distribution and was independent of distance from egg tunnels. There are four or five larval instars. The thermal constant ofA. ruficorneis 571 degree-days (lower temperature threshold, 11.3°C). The predator can feed on all immature stages of the bark beetlesO. erosusandPityogenes calcaratusEichhoff. However, larvae and adults were recorded gnawing bark, and wood particles were observed inside the alimentary canal. In simulated pine tree systems, adults consumed 0.6–1.9 bark beetle eggs or neonates. The combined effect of adults and larvae suggest that this predator might reduce the population of the bark beetles by up to 90% during spring and autumn and by 30–50% during summer.

DOI:10.1093/ee/19.4.1010

出版商:Oxford University Press    

年代:1990

数据来源: OUP