摘要:

Dual-polarization radar recorded insect behavior when a gust flow interacted with a deep, dense cloud of large insects over North Dakota on 4 July 1987. These data reveal areas within the upper parts of the cloud with apparent active modified flight behavior. Disturbed areas were separated from adjacent undisturbed areas by only a few hundred meters. The boundary layer was not capped and circulations were free to rise above an apparent flight ceiling of ≈1,800 m and where temperatures were in the range 12–15°C. Disturbances in some areas extended downward 1,000–1,200 m from the top of the cloud to levels where the temperatures were ≈10°C warmer. Kinematic analysis of Doppler velocities revealed close correspondence between the areas of modified flight behavior and strong updrafts (and in a few instances, strong downdrafts). The data permit at least five explanations for the apparent modified flight behavior. These are passive sorting in updrafts, and active response to turbulence, rates of change of temperature, rates of change of pressure, and the presence of clouds.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.921

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Insect control measures can be effective not only by increasing mortality but also by affecting development and activity. Analysis of the simultaneous effects of a treatment on death times and development times is, however, complicated by difficulties that also arise in analyzing biomedical data in which there are competing causes of death. The theory that has been developed for dealing with these problems, competing risks theory, is reviewed in this article and applied to data from a laboratory study of the effects ofNosema locustaeCanning andN. cuneatumHenry on mortality and development inLocusta migratoria migratorioides(Reiche&Fairmaire). Although the distributions of observed development times are similar among application rates, the use of competing risks methods showed that slower development is associated with increasing doses of bothNosemaspecies. Further analysis of death times showed thatN. locustaeandN. cuneatumhave quite different effects on development and mortality.N. locustaedoes not retard progression to the fifth instar as much asN. cuneatum, but forN. cuneatum, the death rate of inoculated locusts is greatly reduced at the onset of the fifth instar.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.939

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Mating disruption ofEpiphyas postvittana(Walker) using Shin-Etsu dispensers that contained (E)-11-tetradecenyl acetate and (E,E)-9,11-tetradecadienyl acetate was investigated using pheromone traps, tethered virgin female moths, and assessment of larval damage in apples at harvest in small orchard blocks (<0.5 ha). Pheromone trap catches were completely suppressed for 9 mo by a single application of synthetic pheromone. Catches did not return to control levels for 12 mo. Mating disruption, investigated for 94 wk, was completely achieved in 100% of weeks when average weekly release rates were ≥12 mg/ha per h, in 84% of weeks with 8–12 mg/ha per h, and in 68% of weeks with<5 mg/ha per h. The majority of failures to disrupt mating occurred in the following spring. Along with low pheromone release rate, coincident high activity of males outside the orchards (1–2.5 males per trap per day) appear likely to be major factors in 90% of failures to disrupt mating completely within the orchards. A change from pheromone blend close to the natural blend to one with significantly more isomeric impurity (a change from ≈3 to 30%, (Z)-11-tetradecenyl actetate) did not adversely affect efficacy, measured by prevention of trap catch or mating of tethered females. Trap catch 50 m outside treated blocks was correlated with frequency of mating by tethered females 5 m away, but the parameters were not related to fruit damage by larvae at harvest on the nearest orchard border.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.949

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Several baits and baiting techniques were compared in fields of sweetpotato,Ipomoea batatas(L.) Lam., for sampling wireworms of different species:Conoderus scissusSchaeffer,C. rudis(Brown),C. amplicollis(Gyllenhal), andC. falliLane. The baits were seeds of com, wheat, a corn–wheat mixture, rape, cowpea, sorghum, and triticale. These baits were compared with nonbaited soil samples. The relative performance of different baits varied with condition of the baits and length of exposure. The com-wheat mixture attracted more wireworms than the other baits. In the baits, significantly more wireworms were found in the 0–10-cm profile than in the 10–20 and 20–30-cm profiles. No definite relationship was observed between kind of seed bait and wireworm species. Baits removed 1wk after emergence contained significantly more wireworms than similar baits removed 2 and 3 wk after emergence in fields dominated byC. scissusandC. amplicollis.In a field dominated byC. rudis,more wireworms were found following increased exposure of the bait. Bait plants were equally effective following placement in the field at either 1 or 2 wk after germination. Two-week-old bait plants were less effective except the corn–wheat mixture, which was equally effective 3 wk after germination.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.957

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

An isolated population of the red imported fire ant,Solenopsis invictaBuren, was discovered in Lubbock, TX, during August 1985. This find represented the northwesternmost known population in North America, and it had survived since at least 1983. Preceding the 1985–1986 winter, 207 colonies were located and marked, and 85.4% of the colonies survived until the following spring. Of 277 colonies located before the 1986–1987 winter, 47.8% survived until March 1987. Colonies found near brick walls and roadside, concrete curbs were 89.5 and 80.2%, respectively, of the numbers found at the same locations the previous fall. These percentages are significantly greater than those of colonies found in open, more exposed areas (40.0%). The larger number of overwintering colonies found near human-made structures may have been the result of colony survival due to greater insolation and consequently warmer soil temperatures than those in open areas. However, the larger number of surviving colonies could have been a manifestation of location preference resulting from repeated colony movements. Only after persistent and aggressive intervention through the use of insecticides was the population eliminated.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.964

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Effects of cultural practices on populations of wireworms affecting sweetpotato were evaluated, and a comprehensive survey was conducted to determine the preference of wireworms species for corn, sweetpotato, peanut, soybean, turnip, woodland, cowpea, fallow, cotton, tomato, and tobacco. In each of 3 yr, the highest number of wireworms per sample was observed in sweetpotato followed by peanut and corn. Few wireworms were recorded in fallow fields.Conoderus scissusSchaeffer andConoderus rudis(Brown) were most abundant in Georgia.C. scissusandC. rudiswere found in all crops and were most abundant in sweetpotato, whereasConoderus amplicollis(Gyllenhal) was most abundant in corn.Conoderus falliLane abundance was low in all crops. Cropping history influenced the wireworm species composition in sweetpotato. Wireworm populations increased in a crop when grown after sweetpotato, but baited traps of a corn-wheat seed mixture reduced wireworm populations significantly from the sweetpotato hills. Wireworms were more abundant in raised beds than between raised beds. Repeated plowing of the soil reduced wireworm abundance in a field. Abundance was greater in weedy fields than in weed-free fields.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.969

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Terminal shoots from coast live oaks,Quercus agrifoliaNeé, were sampled to determine the abundance and spatial distribution of acorns infested by the filbert weevil,Curculio occidentis(Casey), and the filbertworm,Cydia latiferreana(Walsingham), at a site in northern California during 1989. Nine sampling strata in the tree crown were vertically aligned into blocks of three, each facing a different compass direction (NE, S, and NW). Overall, 25% of all acorns examined on shoots of sample trees revealed signs of insect-boring activity. Acorn numbers were most abundant in May and logarithmically declined throughout the season. The frequency of insect-infested acorns on shoots during the season resembled a random distribution; however, this resemblance was not significant. Peak numbers of infested acorns appeared in mid-September. Within crowns, most acorns occurred in sampling strata within the south-facing section. Significantly more infested acorns occurred in sampling strata within the northeasterly and south-facing sections of the crown. Dissection of 501 acorns revealed infestation rates of 38%. Of those acorns found to contain insect larvae, 66% containedC. occidentisand 27% containedC. latiferreana. Possible mechanisms for explaining the dissimilar distribution of total and infested acorns within crown strata are discussed. The implications of these findings to the development of sampling schemes for ecological studies of acorn and acorn-boring insects are also discussed.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.975

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A geostatistical description of the spatial distribution ofLimonius californicus(Mannerheim) wireworms is presented, as are unbiased estimates of spatial dependence for different sampling scales, patterns, and areas. The spatial structure was usually described by the spherical model, indicating an aggregated spatial arrangement. Localized discontinuity was>0.48 at scales of 5, 10, and 20 m and increased with scale. Spatial dependence occurred at a range of 66 m. Stratified hexagonal sample patterns generally gave more accurate summary statistics, parameter estimates, and r2values for theoretical spatial models than did random sampling. With few exceptions, summary statistics for the subsampling patterns reasonably estimated those for the complete 309-sample grid. However, perception of the spatial structure deteriorated with reduced samples. Frequency distributions estimated by Poisson and negative binomialkdistributions gave similar interpretations as the geostatistical analyses. However, geostatistical analysis is a true spatial analysis and yields information on spatial distribution, whereas traditional “spatial dispersion” methods only infer association from frequency distributions.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.983

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Dispersion patterns of eggs, larvae, and adults ofProdiplosis longifilaGagné were determined for lime orchards in Dade County, Florida, during 1987 and 1989. Dispersion indices generated by Taylor's power law and Iwao's patchiness regression were compared. Taylor's power law provided a better description of variance-mean relationships for eggs, larvae, and adults than did Iwao's patchiness regression. All insect stages exhibited aggregated patterns of spatial distribution (b>1.4). Sample size requirements for fixed levels of precision were determined for eggs and larvae using estimated variance–mean relationships obtained from Taylor's power law regressions. Color sticky traps placed on the tree canopy provided a more efficient method of samplingP. longifilapopulations than ground emergence traps and collection of larval samples.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.996

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Nitrogen fixation, nodulation, and organ dry weights of soybean infested with the larvae of the southern corn rootworm,Diabrotica undecimpunctata howardiBarber, were estimated under controlled conditions. Larval southern com rootworm reduced the nitrogen-fixing activity of mid-vegetative and early reproductive soybean,Glycine maxMerrill. Soybean of both stages responded to the infestation and subsequent injury by increasing nodulation and organ dry weights of below-ground tissues relative to above-ground tissues. Infestation increased the dry weight of small nodules on vegetative plants and caused a 78.6% increase in the total number of nodules on R5 plants. Leaf area as well as leaf and stem dry weight was reduced in vegetative plants by infestation.

ISSN:1754-5692    

DOI:10.1093/ee/21.5.1002

出版商:Oxford University Press    

年代:1992

数据来源: OUP