摘要:

Validation is a critical stage in model development with at least two identifiable types: (1) risk-to-user or cost-benefit criteria for evaluating management models and (2) rigorous statistical procedures to test research models. Each type is discussed along with some quantitative validation tools. We emphasize that selection of inappropriate criteria can lead to unnecessary delays in implementation or use of poorly validated models.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.425

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Production ofParapsyche cardisRoss andDiplectrona modestaBanks was estimated in two first-order southern Appalachian streams. One stream drains a natural undisturbed hardwood watershed and the other a watershed subjected to several disturbances, including clearcutting. Since 1968 the latter has been allowed to undergo natural succession. Both hydropsychid species were univoltine in each stream. Production estimates were higher for both species in the stream draining the disturbed watershed. This was attributed to: (1) More suitable habitat in the disturbed watershed consisting primarily of rock face habitat with large amounts of moss; (2) Higher densities of prey species in the disturbed watershed; and, (3) Potentially enhanced food quality resulting from a 200 fold greater NO3-N concentration in the disturbed stream. The estimates of animal food consumption required to support the combined production ofP. cardisandD. modestawere 11.59 and 3.33 g/m2/yr on the disturbed and undisturbed watersheds respectively. These two species use<0.019% and<0.0063% of the total organic seston passing over each m2/yr on the disturbed and undisturbed watersheds respectively. However, estimates of animal tissue consumption are several times higher than the invertebrate drift from each watershed. The latter suggests that the major impact of these net spinners is on the animal fraction of the seston.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.433

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Studie were conducted in 1978 and 1979 to evaluate the effects of varying twospotted spider mite populations on photosynthesis, transpiration, and productivy of strawberry plants under field conditions. Both photosynthesis and transpiration were significantly reduced by high levels of spider mite populations. Early season infestations caused reductions in physiological parameters at much lower population levels than was necessary to cause similar injury later in the season. Reduced physiological activity of mite-stressed plants persisted until plant recovery was observed following a rapid decline in spider mite populations. The number of fruit produced was significantly increased from plants experiencing low level stress from mite populations. After the initial increase, the number of fruit from infested plants decreased significanyly and the difference was greatest from plants that experienced early season stress. Fruit size was reduced significantly for all mite-stressed plants.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.442

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Neoaplectana bibionisBovien was found to be considerably more effective for disinfesting blackcurrant cuttings ofSynanthedon tipuliformis(Clerck) larvae than were two other insectparasitic rhabditid nematodes,Neoaplectana carpocapsaeWeiser andHeterorhabditis heliothidis(Kahn et al.). This species of nematode caused 99.4 and 99.8% mortality of currant borer larvae in two commercial consignments of canes destined to establish some 12 ha of borer-free plantation.Spraying bundles of cuttings, stacked as a wall, with 30,000N. bibionisinfective juveniles per ml was found to be a feasible method for economically dis infesting blackcurrant cuttings on a commercial scale.No phytotoxic effects were observed following any of the treatments.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.449

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

The infield trap baited with grandlure is widely used to detect the movement of boll weevils,Anthonomous grandisBoheman, into cotton fields in the early spring. Computer analysis of trap spacing indicates that catch probability may be increased 10 to 20% by adjusting the traps away from the usual uniform spacing throughout a field to bring them closer to field borders where weevils are more likely to land first.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.454

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

The combined effects of temperature, relative humidity (RH), and wood moisture content (WMC) on wood consumption and growth ofH. bajuluslarvae in three locations are reported here. The locations and environmental conditions during the 90-day experiment were: house basement, 24.8 ± 0.68°C, 78.1 ± 3.4% RH, 8.7% WMC: house attic, 24.5 ± 10.8°C, 75.5 ± 9.5% RH, 7.6% WMC; laboratory, 29.6 ± 2.3°C, 81.9 ± 5.5% RH, 10.1% WMC. Larvae (n= 16) in the laboratory consumed the largest amount of wood (2,959 mg per larva). The wood consumed by larvae (n= 16) in the basement (2,398 mg per larva) was not significantly different from those in the laboratory. Larvae (n= 17) in the attic consumed less wood (1,086 mg per larva) than those in the laboratory or basement. Results indicate that despite a significant difference between weight classes, small larvae (mean = 55.3 mg, n = 15) consumed nearly the same amount of wood as medium (mean = 151.5,n= 16) and large (mean = 296.9,n= 18) larvae in each location.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.458

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

The host range of a Panamanian moth,Parapoynxprob.rugosalisMöschler, a potential biological control agent against the recently introduced hydrilla,Hydrilla verticillata(L.f.) Royle, was investigated by confining individual larvae (n= 535) in styrofoam cups with a fragment of one of 16 aquatic plant species. Feeding by the larvae was negligible on 10 species, and only hydrilla, coontail (Ceratophyllumsp.), and naiad (Najassp.) showed heavy feeding damage. However, larvae feeding on coontail had such high mortality (24% per day) that they probably would not do extensive damage to this plant in the field. Since these moths show a relatively narrow host range, the insect could be considered for importation into the United States.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.462

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Parasitism of three species ofBrochymena,B. arborea(Say),B. cariosaStål andB. sulcataVan Duzee, byTrichopoda plumipes(Fabricius) was studied in College Station, Tex. Percent parasitism and number of eggs per parasitized host were essentially the same for males and females and for the three host species, except that the mean number of eggs on parasitized hosts was higher forB. sulcatathan forB. cariosa. Overall, hosts collected on black willow,Salix nigraMarshall, and cottonwood,Populus deltoidesMarshall, were more heavily parasitized and showed a higher number of parasite eggs than did those hosts collected on American elm,Ulmus americanaL., or Chinese elm,U. pumilaL.Trichopoda plumipesshowed a marked preference for the abdominal tergites and hind wings as oviposition sites. Of those eggs found, 91% were located on tergites and other areas which were hidden from view by the forewings when the host was at rest, and 97% of the eggs were deposited on the dorsal surface of the host. A relatively low percentage of those hosts bearing hatched tachinid eggs had parasite larvae internally.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.468

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

Densities of up to 25 eggs per flower head ofCarduus acanthoidesL. and up to 25/head ofC. thoermeri2Weinmann were used to evaluate the impact of larval crowding on the survival ofRhinocyllus conicusFroelich (Col.: Curculionidae). InC. acanthoides, increasing egg densities were accompanied by lower survival to the adult stage and significantly lighter weight of emerging adults. Survival was also lower inC. thoermeriwith higher egg densities, but differences in survival and in weights of adults were not significant.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.472

出版商:Oxford University Press    

年代:1981

数据来源: OUP

摘要:

The exposure of larvae of the armyworm,Pseudaletia unipuncta(Haworth), containing the ichneumonid parasites,Hyposoter exiguae(Viereck), to the nematode,Neoaplectana carpocapsaeWeiser, adversely affected the parasites. When armyworms containing 8-day-oldH. exiguaefed on alfalfa leaves treated until runoff with a suspension of 500 or 1000 nematodes/ml, the majority of the parasites which farmed cocoons were infected with the nematode. Only 34 and 14%, respectively, of these cocoons yielded adult parasites in contrast to 93% of the cocoons in the control.Pupae ofH. exiguae,Apanteles medicaginisMuesebeck andChelonussp. in intact cocoons were resistant to infection byN. carpocapsaewhile parasite pupae in intentionally punctured cocoons had infection rates between 56 and 100%. Scanning electron microscope observations on cocoon structure indicated that the resistance of these parasites to infection in intact cocoons was due to the presence of a pore-free layer of silk within the cocoon which acted as a mechanical barrier to the nematode. The impact of other microbial agents andN. carpocapsaeon insect parasites is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/10.4.474

出版商:Oxford University Press    

年代:1981

数据来源: OUP