摘要:

Austrian pine,Pinus nigraArnold, jack pine,P. banksianaLamb., Scotch pine,P. sylvestrisL., and ponderosa pine,P. ponderosaLaws., in the Nebraska National Forest in central Nebraska were examined for infestation and damage byDioryctriaborers. Ponderosa pine and Scotch pine had the largest and second largest current-yearDioryctriaborer infestations, respectively, as estimated by the number of new pitch masses on the trees. The two species also had the largest previous-year infestations (as estimated by old pitch masses) and damage severity ratings. Austrian pine and jack pine were the least infested and damaged species. TheDioryctriaborers present were identified asD. ponderosaeDyar andD. tumicolellaMutuura, Munroe&Ross.

DOI:10.1093/ee/22.4.781

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Feeding rates (mm2/h per larva) of larval Colorado potato beetles,Leptinotarsa decemlineata(Say), were measured in 2- to 2.5-h trials on excised ‘Russet Burbank’ potato (Solanum tuberosumL.) leaflets at constant temperatures from 14 to 42°C. In all instars, feeding rate was greatest at ≈29°C and decreased symmetrically at higher and lower temperatures. Second, third, and fourth instars fed at 42°C. In 24-h trials consisting of repeated 2- to 2.5-h measures at ≈6-h intervals, feeding rates at 23 and 29°C varied among and within groups of larvae, but no consistent diel pattern was detected.

DOI:10.1093/ee/22.4.784

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The parsnip webworm,Depressaria pastinacella(Duponchel), webs together developing umbels of its host plant,Pastinaca sativaL., throughout the course of its larval life. We estimated energetic, time, and material costs of web-spinning behavior for this species. Webworms spent ≈one-third of their time spinning silk; of digested food biomass not expended on respiration, one-fourth was incorporated into silk, and almost 18% of ingested nitrogen was incorporated into silk. Three experiments examined webworm behavior with respect to occupied and unoccupied webs. Caterpillars displaced from their webs occupied empty webs provided to them 87.5% of the time instead of spinning new webs. Moreover, webworms defended their webs against usurping conspecifics. Of 63 staged interactions between web occupants and intruders, 52 were initiated by the residents, and all but one resident successfully defended the web. Finally, when larvae were displaced from their own webs and ‘squatters’ installed, aggressive attacks were equally likely to be initiated by web-builders and squatters. These behaviors are consistent with a high cost of web building because costs and risks associated with aggressive defense of a web presumably do not exceed those expended in constructing a new web or in being without a web.

DOI:10.1093/ee/22.4.791

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

MaleTabanus nigrovittatusMacquart hover as a premating strategy in the early morning over Atlantic coastal salt marshes. These males are distributed with peak densities near mosquito ditches and with fewer hovering males farther from the ditch. Multivariate analysis indicated that male density or the distance between individuals is an important factor in structuring hovering male spatial distribution. When compared with previously published data, male densities match peak emergence of females.T. nigrovittatusnumbers are lowest directly adjacent to mosquito ditches, whereTabanus conterminus(Walker) tends to hover, suggesting that spatial separation may contribute to reproductive isolation in these two sibling species.

DOI:10.1093/ee/22.4.796

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Within-plant distribution and within-field dispersion ofSpissistilus festinus(Say) nymphs on conventionally planted and tilled soybeans,Glycine max(L.) Merrill, were quantified over a 2-yr period at two experimental sites. Within-plant distribution (vertical and horizontal location) was more closely associated with vegetative development in 1986 than in 1987. The mainstem node with the most nymphs, designated the most likely node (MLN), represented the location of 50% or more of all nymphs through 4 July (V6–V7) and at least 30% through 10 August (Vl3–V18). From plant emergence until first bloom (R1), 100% of the nymphs were found on either the mainstem, mainstem petioles, or the first lateral branch node. However, from R1 until the end of the season, significantly more nymphs were found on mainstem petioles, and twice as many nymphs were associated with lateral branches than with the mainstem. Higher nymphal densities and a greater proportion of infested plants occurred in 1986 than in 1987. Indices of dispersion calculated from individual plant samples suggested greater aggregation of nymphs than did values reported for larger sample units such as the ground cloth. Iterative nonlinear regression of proportion infested plants against mean density allowed estimation of Taylor's coefficients that were used to develop sequential sampling plans appropriate for enumerative and presence-absence methods. Results indicated that nymphs did not reach damaging levels during any of the sampling periods.

DOI:10.1093/ee/22.4.802

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Constant high temperature regime (30, 34, 37, and 40°C) for 1–5 h decreased mean survival of nymphal and adult stages ofMonelliopsis pecanisBissell andMelanocallis caryaefoliae(Davis) with increasing temperature and time of exposure. Constant low-temperature regime (0, 6, 12, and 15°C) decreased aphid survival with decreasing temperatures and increasing time of exposure. A temperature by aphid interaction was observed, with the greatest mortality being at the extreme high (37 and 40°C) and low (0 and 6°C) temperatures. Aphid stages showed differences in tolerance to all temperature levels. Third and fourth ins tars and adults of both species withstood a wide range of temperatures better than first and second instars under either regime.M. pecanistolerated low temperatures better thanM. caryaefoliae, but at high temperatures,M. caryaefoliaewas more tolerant. Air temperature fluctuations within a pecan tree were measured during July with temperature probes. Air temperature was slightly higher at the edge of the tree crown than near the trunk, otherwise temperatures were very uniform within the tree crown for a given hour of the day.

DOI:10.1093/ee/22.4.810

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

This study was conducted to assess the reproductive potential of first- and second-generationRhopobota naevana(Hübner) females collected from a commercial cranberry farm and reared on field-collected foliage under controlled conditions. Between 90 and 95% of eggs laid by first-generation females hatched within 2 wk of oviposition, whereas most (80–95%) eggs laid by second-generation females entered diapause. In 1990, when cranberry plants were heavily fertilized with nitrogen, total fecundity of the two generations was similar. In 1991, when a minimal amount of nitrogen fertilizer was applied to the plants, first-generation females were more fecund than second-generation females, and diapause eggs laid by second-generation females were larger than nondiapause eggs laid by first-generation females. Ovarian maturation proceeded more slowly in the second generation than in the first. Duration of pupal stage, adult stage, and emergence period were longer in the second generation than in the first. Male pupae weighed less than female pupae, and males emerged slightly before females. Results suggest that first-generation fireworm females allocate resources gathered during larval feeding to production of as many eggs as possible, whereas second-generation females produce fewer, larger eggs. However, second-generation females fed nitrogen-rich foliage may be able to produce more eggs than usual.

DOI:10.1093/ee/22.4.818

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

In 1989 and 1990, after the egg-laying period of the white pine weevil,Pissodes strobi(Peck), infested leaders of white pine,Pinus strobusL., were harvested in a young plantation. To test the influence of bark quality modification on weevil development, leaders were set directly into water or kept dry. The number of insects emerging per leader and the adult mean weight of the weevils were measured for leaders exposed to both treatments. During the second year, the data were also collected on weevil development in the field. Results show that the white pine weevil can complete its development on cut leaders. However, the dry treatment significantly reduced the mean weight and the number of weevils when compared with the wet treatment. The number of insects emerging per leader was less affected by treatment than was the adult mean weight.

DOI:10.1093/ee/22.4.824

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Freeze tests were conducted throughout the winters of 1987–1988 and 1989–1990 to determine the comparative supercooling points ofUrophora affinisFrauenfeld andU. quadrifasciata(Meigen) larvae, and to assess the effects of site and midwinter temperature change on the supercooling ability ofU. affinis. The supercooling capacity ofU. affiniswas significantly greater than that ofU. quadrifasciata; the mean supercooling point forU. affinisduring the two winters was −35.1°C compared with −31.0°C forU. quadrifasciata. Regression analyses showed a significant, negative quadratic relationship between supercooling point and collection date during the winters of 1987–1988 and 1989–1990 for both species. Differences in supercooling ability amongU. affinislarvae collected from six different Bitterroot Valley sites were infrequent, of small magnitude, and inconsistent over the 2 yr sampled. The supercooling ability ofU. affinismaintained at +25°C was significantly less than that ofU. affinisin the field but the supercooling ability ofU. affinismaintained at or slightly below freezing was generally comparable with that ofU. affinisin the field. Based upon this study, both fly species can be expected to survive the winter in most areas of western Montana and the Pacific Northwest, but onlyU. affinisshould be considered for release in eastern Montana and other regions east of the Continental Divide where winter temperatures are often lower than −35°C.

DOI:10.1093/ee/22.4.831

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The effect of different aggregation pheromones on attraction ofCarpophilus hemipterus(L.),C. mutilatusErichson, andC. humeralis(F.) was demonstrated in olfactometer and field trials in Israel. Aggregation pheromones act as synergists to attractCarpophilusspp. to host volatiles. Captures in traps baited with the pheromone–host volatiles combinations were higher than in traps baited with host volatiles alone.Carpophilusspp. aggregation pheromones are not entirely species-specific, and pheromones belonging to one species may also enhance attraction of other species. This cross-attraction is not surprising because congeners do have pheromone components in common. Thus, pheromones ofC. lugubrisMurray andC. freemaniDobson enhanced attraction ofC. hemipterusto host volatiles, whereasC. humeralisattraction to host volatiles was enhanced by the pheromones ofC. hemipterusandC. lugubris.C. mutilatusexhibited a high degree of activity to its own pheromone. Aggregation pheromones ofCarpophilusspp. do not have any effect onHaptoncus luteolus(Erichson). The possibility of using host volatiles–pheromone combinations for monitoring and perhaps even for control of these pests (by mass-trapping or disruption of egg laying and mating) appears very promising.

DOI:10.1093/ee/22.4.837

出版商:Oxford University Press    

年代:1993

数据来源: OUP