摘要:

The effects of citrus limonoids, applied topically to potato foliage, on colonization and oviposition by Colorado potato beetle,Leptinotarsa decemlineata(Say), adults were quantified in no-choice laboratory assays, choice and no-choice greenhouse arena observations, and small-plot field tests. In laboratory assays the oviposition rate decreased with increasing limonoid dosage and exposure time. Oviposition suppression time also increased with increasing dosage. Over a 9-d observation period, ED50s (50% reduction in fecundity) were 7.2 mg/ml, 1.93 mg/ml, and 0.64 mg/ml for 3-, 6-, and 9-d exposures, respectively. Adult colonization and oviposition rates were significantly reduced by limonoid treatment in both greenhouse and field tests. The seasonal density of adults was significantly reduced with a low rate (3.6 kg/ha) application of limonoids, whereas a higher application rate (10.8 kg/ha) was needed to reduce significantly the seasonal egg mass density in the field. The total number of treatment applications (1, 2, or 3) made at 3-d intervals significantly lengthened the period during which colonization and oviposition were inhibited, but did not affect seasonal densities of either adults or egg masses. These results indicate that citrus limonoids have very good potential for use in pest management.

DOI:10.1093/ee/24.5.1275

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Age-specific life table studies were conducted on the Russian wheat aphid,Diuraphis noxia(Mordvilko), to evaluate the effects of using a barley–benzimidazole agar system onD. noxiagrowth, reproduction, and survival. Weibull functions, linear and nonlinear regression, a modified Sharpe and DeMichele biophysical model (MSDBM), and Maxima functions were used to estimate or model survivorship patterns, the lower temperature threshold for development, the upper temperature inhibition threshold, nonlinear aspects of rates of development, and mean daily fecundity patterns ofD. noxia, respectively. The Weibull function provided a good fit to the aphid survivorship patterns (R2= 0.95). The lower developmental threshold and the upper temperature inhibition threshold for the Russian wheat aphid using the barley–benzimidazole agar system were estimated to be 5.2 and 30.3°C, respectively. The MSDBM also provided an excellent fit to nonlinear aspects of developmental rate trends (R2= 0.996). Maxima functions were found to adequately describe patterns of daily fecundity at 3 of the 4 constant temperatures examined. The mean longevity ofD. noxiareared on the barley–benzimidazole agar system was greater than those reported by other authors using wheat- and rye-benzimidazole agar systems. Longer nymphal devplopment times using the barley–benzimidazole agar system resulted in a lower intrinsic rate of increase for Russian wheat aphids reared at 19.5°C, than those observed by other authors using wheat- and rye-benzimidazole agar systems, and a developmental threshold that was higher than those reported by other authors for Russian wheat aphids grown on wheat using other plant growth systems.

DOI:10.1093/ee/24.5.1284

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Feeding rates of laboratory-rearedMelanoplus sanguinipes(F.) nymphs were measured in 3-h trials at 15, 20, 26, 30, 35, 40, or 45°C. Feeding rates increased with temperature to a maximum, then decreased at higher temperatures. Maximum feeding rate occurred at 35°C in 1st and 2nd instars, and at 40°C in 3rd, 4th, and 5th instars. In a subsequent 24-h trial, mean hourly feeding rates at 30, 35, or 40°C agreed with those of the 3-h trials. A linear model was used to describe feeding rates at temperatures at or below that at which rate was maximum, and a nonlinear model was used to describe the feeding rate trends over the full range of experimental temperatures. Using the linear model, estimated low-temperature feeding thresholds ranged from 13.5°C for 2nd instars to 15.9°C for 1st instars. Using the nonlinear model, estimated low-temperature feeding thresholds were near 13°C for all but 3rd instars, for which it was near 8°C; modeled temperatures at which feeding was maximal agreed with measured values, and the modeled upper temperature threshold for feeding was between 45 and 46°C for all instars. The linear and nonlinear models are similar at temperatures below that at which feeding is maximal, but the linear model overestimates feeding at higher temperatures. Application of the feeding rate functions to field conditions requires improved understanding on the determinants of body temperature under field conditions, and on the relationship between feeding and wastage.

DOI:10.1093/ee/24.5.1291

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Larval survival, pupal mass, adult emergence, fecundity, and natality in the house fly,Musca domesticaL., are not influenced by the levels of calcium or nitrogen in feces of caged laying hens,Gallus gallusL.. Reduced pupal mass, low fecundity, and low natality in flies are correlated with increased manure phosphorus concentration. Estimated pupal mass is inversely proportional to manure phosphorus content and decreases by 2.6 ± 0.5 mg for each 1.0% increase in the phosphorus level. The concomitant decrease in estimated mean fecundity is 27.6 ± 1.5 eggs per fly. Female flies that emerge from 16.5-mg pupae (larvae reared in-low-phosphorus manure) produce an estimated 5 times more eggs (146.3 versus 26.6) than females that emerge from 5.2-mg pupae (larvae reared in high-phosphorus manure).

DOI:10.1093/ee/24.5.1297

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Adult females of the southern masked chafer,Cyclocephala luridaBland, produce a volatile sex pheromone that attracts conspecific males. Previously we documented that extracts of 3rd-instarCyclocephalaspp. grubs contain one or more compounds that attract males and stimulate copulatory attempts when these males arrive at the source of the odor. Attraction of males to larvae appears to be undocumented for any other insect species. We examined developmental expression of the production of this attractant withinCyclocephalaspp., and evaluated hexane extracts of other species of scarabaeid grubs for attractiveness toC. luridaor conspecifics. We found that the attractant is not limited to the postoverwintering last instar, but rather is present in all larval stages and in male and female pupae. Extracts ofCyclocephalaspp. grubs also attracted males of the northern masked chafer,Cyclocephala borealisArrow. Hexane extracts of 3rd instars of Japanese beetles,Popillia japonicaNewman, and green June beetles,Cotinis nitidaL., were not attractive to maleC. lurida, indicating that there is some phylogenetic specificity to this unusual production of a sex-specific attractant. Third instars ofC. nitidado not attract conspecific males. Studies of male attraction to conspecific immature stages inCyclocephalaspp. and other Scarabaeidae may provide insights into the evolutionary origins of chemical communication systems.

DOI:10.1093/ee/24.5.1302

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We investigated the effect of species and age of foliage eaten by gypsy moth,Lymantria dispar(L.), larvae on the entomopathogenic fungusEntomophaga maimaigaHumber, Shimazu et Soper. Time to death, percentage mortality, and numbers and types of spores (conidia and azygospores) produced after host death were evaluated for cadavers of L.disparlarvae that had eatenQuercus rubraL.,Acer rubrumL.,Pinus strobusL., orLarix kaempferi(Lamb.) Carr. Throughout this study, mortality levels were equivalent across plant species, suggesting a lack of any strong foliar-induced inhibition of conidial penetration of the cuticle. Significantly fewer cadavers of larvae that had eaten A.rubrumproduced conidia or azygospores compared with cadavers of larvae that had eaten L.kaempferi, and E.maimaigadeveloped more slowly in larvae eating A.rubrum. Larvae eating A.rubrumdeveloped more slowly, supporting a hypothesis that host stress negatively influences development of this fastidious pathogen. Although Q.rubrasecondary plant compounds are known to fluctuate as leaves develop during spring, pathogenicity attributes showed no concurrent trend in variation. In comparing 4 of the fungal isolates tested, fewer cadavers of larvae killed by one Japanese isolate produced conidia and this isolate was slower in developing, demonstrating the potential for variability in pathogenesis among pathogen strains.

DOI:10.1093/ee/24.5.1307

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The vulnerability of broom snakeweed,Gutierrezia sarothrae(Pursh) Britton&Rusby, to herbivory by the grasshopper,Hesperotettix viridis(Thomas), was quantified by placing various densities of grasshoppers on individual caged plants. Field experiments were conducted in the summers of 1989 and 1990 at 2 shortgrass prairie locations in eastern New Mexico. In general, grasshoppers removed most photosynthetic tissue from small plants within 7 d at an initial density of 16 grasshoppers per plant, and in ≈14 d with an initial density of 8 per plant. Grasshopper densities of 2 per plant rarely consumed all photosynthetic tissue, irrespective of plant size, during caged experiments. Although not consistent over sites and years, grasshopper feeding reduced plant volume and the number of photosynthetic stems from small and medium plants at densities of 8 and 16 grasshoppers per plant. Grasshopper defoliation caused 8, 23, 34, and 47%G. sarothraemortality at densities of 2, 4, 8, and 16 grasshoppers per plant, respectively. Grasshopper feeding pressure was significantly correlated with observed defoliation and suggests feeding by>4H. viridisper plant results in a significant decrease in aboveground photosynthetic biomass.

DOI:10.1093/ee/24.5.1315

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We studied the influences of mating history, parental age, pupal weight of parasitoids, host deprivation, and host size on the reproductive potential and sex ratio ofCatolaccus grandis(Burks), a parasitoid of the boll weevilAnthonomus grandis grandis(Boheman). Absence of hosts for 5 or 10 d reduced the fecundity ofC. grandisfemales by 36.8 and 39.5%, respectively, compared with parasitoids continually exposed to host larvae. An acceptable sex ratio (65% females) in the propagation system was maintained if a ratio of 3 males per female parasitoid was used during the 1st h of mating, immediately after emergence. As female adults aged from 5 to 10 d, the percentage of female progeny increased from 64.0 to 77.2, respectively. However, a further increase in female age, from 20 to 25 d, resulted in a decline in percentage of female progeny from 54.0 to 48.5. The proportion of female progeny increased with the size of the host parasitized. A significant correlation was found between weight of female pupae ofC. grandisand their fecundity during the first 30 d of oviposition. These data will be used to optimize mass rearing ofC. grandisfor inoculative and augmentative releases to suppress boIl weevil populations in cotton fields.

DOI:10.1093/ee/24.5.1322

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

For 4 yr, we studied the host-pathogen relationship of the microsporidiumThelohania solenopsaeKnell, Allen, and Hazard within field populations of the black imported fire ant,Solenopsis richteriForel, in Argentina. We established and monitored 6 field plots having a high density of fire ant colonies, many infected with the microsporidium. The density of colonies, initially 162 colonies per hectare, decreased to 28 colonies per hectare. The percentage of infected colonies, initially 22.4%, increased to 35.7% and was negatively associated with the density of colonies but positively associated with rainfall.T. solenopsaewas the only known natural enemy of fire ants present consistently and in high levels within the plots. We suspect it is one of the main factors responsible for decreases inS. richteripopulation densities.

DOI:10.1093/ee/24.5.1328

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We studied the effects of densities of ectoparasitoids (per liter of cage volume) and host-parasitoid ratios on the reproductive potential of parasitoid females. Ectoparasitoid,Catolaccus grandis(Burks), densities were varied from 3.8 to 37.7 females per liter volume of oviposition cages (petri dishes). Host-parasitoid ratios ranged from 0.2 to 20 3rd instars of the boll weevil.Anthonomus grandis grandis(Boheman), per parasitoid female per day. Fecundity ofC. grandisfemales was not affected by changes in the density of female adults in oviposition cages. However, adult mortality increased when female parasitoid density exceeded 15 females per liter of cage volume. Mean percentage of parasitism of the boll weevil hosts decreased from 100 to 33% when the host-parasitoid ratio increased from 0.2 to 20.0 weevil larvae perC. grandisfemale per day. Parasitoid fecundity was inversely proportional to the percentage of parasitized host larvae. A higher proportion (69–75%) of fertilized eggs were oviposited when host-parasitoid ratios were between 1 and 20 host larvae perC. grandisfemale than when ratios were<1 host per female (40–41%). Low host-parasitoid ratios reduced the rate of reproduction inC. grandis, whereas high parasitoid densities increased intraspecific competition and parasitoid mortality. Under laboratory conditions, the most efficient host–parasitoid ratio was 5–15 host larvae per female parasitoid per day.

DOI:10.1093/ee/24.5.1333

出版商:Oxford University Press    

年代:1995

数据来源: OUP