摘要:

The author reviews the complex of interrelationships embracing plant-arthropod and higher-level, arthropod-arthropod interactions, as related to natural control phenomena. Included are not only biotic control agents which determine paths and extent of energy flow, but also the evolutionary implications of how this has come to be. Examples of the way in which predaceous (or parasitic) arthropods of primary, secondary, and tertiary order may influence the competitive status of plants, and thus the composition of respective species in vegetation, are considered. We also consider: development by plants of their own resistance to phytophagous arthropods; counterselection among specialized phytophagous species in order to stay in the game; and circumvention of the biological control action of natural enemies of specialized phytophagous species, thus relieving the continuing selective pressure on the plant to offset the plant's countermeasures.The author concluded that plant resistance to phytophagous arthropods, and the interplay of these relationships, the interplay among the plant hosts and their phytophagous predators (including parasites), and among the latter and their own carnivorous predators (including parasites), and at higher levels as well, have had striking influences in the evolution of species, and in their functional, dynamic roles in explaining the population dynamics and energetics of complex communities.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.1

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

This analysis was designed to estimate the impact on crop prices and land use of producing cotton and corn with and without insecticides. A nationwide linear-programming model for a population of 280 million people in the year 2000 was employed to calculate crop costs and land-use patterns that could be expected for several different restrictions regarding land and insecticide use. Without U.S. government acreage controls (in which case, crops could be grown in regions most suited for their production), national crop production with or without insecticides was more efficient and was ca. 50% less expensive than production under a land retirement program. Without U.S. government acreage controls, the calculated costs of growing cotton and corn without insecticides were 11 and 1% greater, respectively, and required 2.1 million acres more land than with insecticide use. Based on various analyses, the conclusion was that the costs of producing crop commodities without insecticides on corn and cotton are slightly greater than the costs of producing these commodities with insecticides and without government acreage controls. However, corn and cotton commodity-production costs without insecticides are considerably less than the cost of producing the commodities with insecticides and under U.S. government acreage controls. Hence, restrictions on land use apear to have much more of an influence in causing higher crop prices than restrictions on insecticide use.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.10

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

After distillation, the autophagostimulant activity ofCulex pipiensL. larval water (millipore-filtered water in which kaolin-glutted larvae have been held overnight at a density of 1–3/ml) was found in the residue, whereas distillate fractions were inactive. After washing larval water with ether, virtually all activity was found in the aqueous phase. These separatory characteristics distinguish theC. pipiensautophagostimulant from growth-inhibiting factors produced by larvae of other mosquito species. More potent phagostimulant activity, also ether-insoluble, occurred in overcrowded larval water (10 larvael/ml, with restricted surface area and food provided for 3 days), but no evidence was obtained that such waters contained a growth-inhibitory factor of the sort produced byCulex quinquefasciatusSay larvae. Water in whichC. pipienspupae or eggs had been held overnight sometimes stimulated increased larval ingestion, but generally the activity was trivial vs. that of larval water. Larval, pupal, and egg waters elicited preferential oviposition in choice tests vs. distilled water. For larval water, oviposition-inducing activity was most evident, after fractionation procedures, in the 1st distillate collected, showing that the larval autophagostimulant (not present in distillates) and the principal oviposition attractant are different materials. The ecological implications of the several mosquito-larval factors now known are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.21

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

Significantly moreInopus rubriceps(Macquart) males fly beneath rather than above 54 cm, irrespective of crop height. In clearings fewer males were trapped at each successive height interval, namely 16–54, 82–121, and 148–186 cm above the ground. Within a 2.5-m-tall crop, no significant difference was detected in the number of males flying at the 2 higher intervals. Traps baited with virgin insects failed to attract either sex. AdultI. rubricepswere not observed to exhibit a strong color preference; but red traps caught significantly fewer flies than did traps of any other color tested. Sticky traps revealed that since the last survey,I. rubricepshad spread ca. 1.7 km into previously uninfested regions. Two species of dragon flies and 1 species of frog were found to be preying onI. rubricepsadults. 92.3% of eggs oviposited by wild females subsequently hatched. Significantly more soldier flies pupate under weeds than in soil exposed to the sun.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.29

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

Nine fungicides and 14 insecticides and acaracides were tested in vitro on various isolates of the entomopathogenic fungi,Beauveria bassiana,Verticillium lecaniiandVerticilliumsp. Two techniques were employed: for Verticillium, a “poisoned-bait” method, showing growth inhibition; forB. bassiana, a poisoned-agar disc method, showing inhibition of conidial germination.All chemicals except white summer oil caused some inhibition to Verticillium growth at 10−4of the recommended dosages for use.Great variations in sensitivity toward a particular fungicide (e.g., captan, copper oxychloride, dinocap, binapacryl) were found among isolates of the same fungal species of both genera, and were also observed with some insecticides (e.g., trichlorfon and narrow-range paraffinic oil onVerticillium).Among the fungicides, benomyl (methyl 1-[butylcarbamyl]-2-benzimidazole carbamate) and maneb caused the greatest inhibition of all isolates of both genera at recommended dosages and at 10−1concn, indicating that their use in field or grove would endanger the fungi. At recommended dosages, copper oxychloride and dinocap were the most innocuous to all the fungi (with the exception of 1 isolate ofB. bassiana). Binapacryl had no effect on spore germination ofB. bassianabut moderately inhibited growth of most isolates ofVerticilliumspp. Daconil 2787™ (tetrachloroisophthalo-nitrite) proved moderately fungitoxic toVerticilliumand less so toB. bassiana.Among insecticides, sodium fluorosilicate, dichlorvos, and chloropyrifos at recommended dosages were strongly inhibitory to growth ofVerticiliumspp., but only sodium fluorosilicate inhibited germination ofB. bassiana.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.33

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

While southern meadowlarkSturnella magna argutulla(Bangs) does destroy sprouting corn, both stomach contents analysis and field observations show that these birds are largely beneficial. Major stomach components include: billbugs (Curculionidae),Prosapia bicincta(Say),Mocis latipes. (Guenee), cutworms (Agrotinae), grasshoppers (Acrididae), and click beetles and wireworms (Elateridae). Beneficials were relatively light in these contents. In addition to corn, vegetable matter included small amounts of grass seed (Paspalum) and dayflower seed (Commelina diffusa(Burm.) F.). Based on observations of meadowlark habits, non-lethal remedial action is suggested. Shooting the birds should be a last resort.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.39

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

Selection and hybridization experiments were conducted to explore the possibility of improving parasitization inTrichogramma. Several biparental stocks were hybridized and selected for their ability to live and reproduce within the temperature extremes likely to be encountered in the release area. In a uniparental stock, selection was made for locomotion, heat tolerance, a combination of locomotion and heat tolerance, and the ability to find hosts. Effects of these experiments were evaluated in field cages placed over cotton plants. No increase In parasitization resulted from the biparental crossings, and selection for temperature adaptation to the release area significantly reduced parasitization. The selection program for the uniparental stock produced positive results which were statistically significant at the 10% level. Greater significance might have been obtained if the program had been carried on for more generations. However, this type of selection program has limited application.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.43

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

Captures of maleTrichoplusia ni(Hübner) in cylindrical electric-grid traps baited with synthetic sex pheromone, declined with increasing elevation from 2 to 10 ft above ground. Collections ofManduca sexta(L.) in similar traps baited with virgin females were not affected significantly by the same range of elevations. Collections ofT. niwith 12-, 18-, and 24-in.-diam grids, but with the same electrode spacing (½ in.), did not differ significantly; however, ¼-in. electrode spacing was 38% more effective than ½-in. spacing on the 12-in.-diam grids. The largest number ofM. sextamoths was caught by the smallest-diameter grid, and the size of collections decreased as the diameter increased.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.49

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

A field study was conducted, 1971–72, in central Iowa, to determine whether females of several strains of the European corn borer,Ostrinia nubilalis(Hübner) and 2 preparations of synthetic lure could successfully compete in attracting feral male European corn borer adults. Females were from Georgia, Iowa, Minnesota, New York, and Quebec. The synthetic lures used werecis-11-tetradecenyl acetate (Z-11-tda) isomerically pure and Z-11-tda containing 8.5%trans(E) isomer. A large segment of the male Eureopean corn borer population in central Iowa is attracted to a source that emits pure or relatively pure Z-11-tda and responds to Georgia (southern ecotype), Minnesota, and Quebec (northern ecotype), as well as Iowa (central ecotype) females, but shows little response to New York females. Nightly drops of 6–12°C after 1700 h and temperature plateaus of 2 or more consecutive h, and high relative humidity, should usually occur to produce searching and attraction activities of the Iowa male and the Georgia, Iowa, Minnesota, and Quebec females, respectively. Wind direction was partially responsible for interaction between attractive sources and males at 28 m. A field by attractant interaction showed that the corn borer moths inhabiting the edge of each experimental cornfield were in a contagious (clumped) distribution.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.51

出版商:Oxford University Press    

年代:1974

数据来源: OUP

摘要:

Erythroneura lawsoniRobinson (Homoptera: Cicadellidae), specific to sycamore, was studied in east-central Illinois in 1972, under both laboratory and field conditions. Adult. females laid 4–6 eggs/week during a 4–5 week oviposition period. Eggs hatched within 15 days, and 5 nymphal instars followed, with a mean development time of 3–5 days/instar. Mean generation time was 41 days, and 4 partially overlapping generations occurred in 1972.This species coexists with 4 other leaf-sucking insects on sycamore:Empoasca fabae(Harris),Empoa platanaChristian (Cicadellidae),Corythucha ciliata(Say) (Tingidae) andPlagiognathus albatus(Van Duzee) (Miridae); the last 3 species are specific to sycamore. The species show differences in temporal and spatial exploitation of sycamore leaves, so that overlap of feeding niches is small.Empoasca fabaefeeds on main viens,Erythroneura lawsonion the leaf blade close to larger veins,Empoa platanaon the leaf blade distant from veins, and the maximum niche overlap seen between these species is 38%.C. ciliatafeeds on the whole area of the leaf blade, and thus overlaps other species extensively, 84% forErythroneura lawsoniand 80% forEmpoa platana. But overall overlap, when both time and space are considered, is reduced to a maximum of 63% betweenC. ciliataandE. lawsoni, and to much less (0–39%) for other species combinations.The sycamore leaf offers a mosaic of microhabitats which allows niche diversification and specialization in the leaf-feeding guild.

ISSN:1754-5692    

DOI:10.1093/ee/3.1.59

出版商:Oxford University Press    

年代:1974

数据来源: OUP