摘要:

Changes in geographical ranges and spatial extent of outbreaks of pest species are likely consequences of climatic change. We investigated potential changes in spatial distribution of outbreaks of western spmce budworm,Choristoneura occidentalisFreeman, and gypsy moth,Lynumtria dispar(L.), in Oregon and Pennsylvania, respectively, using maps of historical defoliation, climate, and forest type in a geographic information system. Maps of defoliation frequency at a resolution of 2 × 2 km were assembled from historical aerial survey data. Weather maps for mean monthly temperature maxima and minima and precipitation over 30 yr were developed by interpolation. Relationships between defoliation status and environmental variables were estimated using linear discriminant analysis. Five climatic change scenarios were investigated: an increase of 2°C, a 2°C increase with a small increase and a small decrease in precipitation, and projections of two general circulation models (GCMs) after 100 yr at doubled carbon dioxide. With an increase in temperature alone, the projected defoliated area decreased relative to ambient conditions for budworm and increased slightly for gypsy moth. With an increase in temperature and precipitation, defoliated area increased for both species. Conversely, defoliated area decreased for both when temperature increased and precipitation decreased. Results for the GCM scenarios contrasted sharply. For the other, defoliation by budworm was projected to cover Oregon completely, whereas no defoliation was projected by gypsy moth in Pennsylvania. For the other, defoliation disappeared completely for budworm and slightly exceeded that under ambient conditions for gypsy moth. The results are discussed in terms of current forest composition and its potential changes.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.1

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Ability to predict the timing of phenological events (herein termed target events) is an important component of gypsy moth,Lymalltria dispar(L.) management programs and integrated pest management programs in general. Several simulation models have been developed that, in part, demonstrate their validity for predicting events at individual locations. The framework described in this article extends the use of these models to be able to make predictions (i.e., create maps) for heterogeneous landscapes. An algorithm is presented that can predict the time that a target event will occur anywhere in a landscape using temperature, a digital elevation model, linked egg hatch and larval development models, and a linear function that relates elevation to the Julian date when a given target event will occur. The algorithm was validated with four data sets collected from Virginia, West Virginia/Pennsylvania, and Utah. Model predictions were satisfactory for the Virginia data sets and differed significantly from those for West Virginia/Pennsylvania and Utah data sets. Potential sources of error are discussed. Target event maps are presented that demonstrate how this landscape framework can be used in gypsy moth management programs.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.10

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Field research was conducted during 1990, 1991, and 1992 to examine effects of plant density on rice water weevil,Lissorhoptrus oryzophilusKuschel, oviposition in rice,Oryza sativaL. Results of the plant density study showed that there was a trend for more eggs per plant at lower densities, but a trend toward more eggs per unit area with higher plant densities. Plant densities influenced rice water weevil oviposition during the first 3 wk of permanent flooding. However, plant spacing cannot be manipulated to control rice water weevil infestation because recommended optimum plant densities do not differ significantly in their effect on oviposition.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.19

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Apterous adult and nymphalRhopalosiphum padi(L.), previously reared on plants infected with barley yellow dwarf virus (BYDV), were subjected to eight perturbations (wind, rain, herbicide, coccinellid predators, crowding, mechanical disturbance, drought, and virus-infected plants) to determine effects on aphid dispersal and pattern of local spread of BYDV to oats in greenhouse experiments. Viruliferous aphids, caged overnight on oat plants in a 25-plant area (infection focus) in the center of each 625-plant plot, were subjected to a given perturbation after cages were removed and then allowed to move freely within the plot for 2 d. Presence of virus-infected plants outside the infection focus provided indirect evidence of aphid movement and direct evidence of virus spread. All types of disturbances except rain caused movement of apterous aphids and spread of BYDV. For all except the rain perturbation, controls were pooled and compared by paired t-tests with means of three indices of infection pattern (incidence, total distance, and average distance) for each experimental treatment. Incidence of infection (number of infected plants located outside the infection focus) in treated plots was significantly greater than pooled controls for the crowding, predator, wind, and herbicide perturbations. Total distance of infection (the sum of distances from the central plant in the infection focus to each infected plant outside the focus) was significantly greater in mechanical disturbance, crowding, predator, drought, wind, and herbicide perturbations than in controls. Average distance of infection (total distance divided by incidence) in treated plots was significantly greater than in the pooled controls for the drought, wind, and virusinfected oat treatments.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.24

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Megachile rotundata(F.) was used to study sublethal effects of carbaryl bran bait on a representative solitary nesting bee. Adult females were fed a 25% honey solution contaminated with 2 mg of commercially formulated carbaryl bran bait (2% [AI]) for 4 d and then were released into a greenhouse to nest in wooden blocks. Bees fed contaminated honey performed as well as bees fed plain honey solution. No differences were observed in number of days spent nesting, rate of cell production, offspring survival, investment in offspring, or offspring weight and sex ratio between carbaryl-treated and control bees. Diapausing bees from both carbaryl and control treatments tended to be larger than those emerging in the same season (emergent bees). We also found no sublethal effects onM. rotundatalarvae. Larvae fed provisions contaminated with 1 or 2 mg of carbaryl bran bait gained as much body weight as those fed uncontaminated provisions. We conclude that the 2% [AI] carbryl formulation of bran bait is likely to be the least detrimental to solitary bee pollinators of any insecticide thus far used to control grasshoppers on rangeland.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.34

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Changes in nitrogen content of poinsettia,Euphorbia pulcherrimaWilldenow (Euphorbiaceae), is an important factor influencing its acceptability and suitability to the sweetpotato whitefly,Bemisia tabaci(biotype B) (Gennadius). More whiteflies were found on fertilized plants than on nonfertilized plants. Higher oviposition on ammonium nitrate treated plants than on nonfertilized or calcium nitrate treated plants suggests that acceptability of a plant by the whitefly is in response to plant cues. These cues reflect changes in nitrogen content and are perceived during probing of the leaf surface by female whiteflies. Although more crawlers were produced from eggs laid on nonfertilized or calcium nitrate treated plants than on ammonium nitrate-treated plants, more adults were produced from fertilized plants than from nonfertilized plants. High mortality during the crawler and young nymphal stages on nonfertilized plants could be caused by nutritional limitations of unfertilized plants.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.40

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Gypsy moth,Lymantria dispar(L.), adults and fourth instars reared from first instar on diet enriched with 3 g rubidium cloride (RbCl) per liter acquired the rubidium (Rb) tag without affecting their phenology or survival. The tag was retained in fourth instars at significant levels for 5 d after removal from the Rb-enriched diet. Loss of Rb after transfer from Rb-enriched diet to diet without Rb was described by a nonlinear regression model of the log of Rb concentration against days after transfer. AdultCarabus nemoralisMüller that consumed Rb-tagged fourth instars acquired the tag. Rb concentration in the beetles was positively correlated with the number of larvae eaten and negatively correlated with the number of days since feeding.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.46

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The effect of consuming low doses of E-64, a cysteine protease inhibitor, on life history parameters ofEpilachna varivestisMulsant, the Mexican bean beetle, was evaluated in bioassays in which E-64 was applied to lima bean leaves. Mortality, larval growth rates, and adult reproductive patterns were monitored and used to estimate life history parameters. Ingestion of this low dosage of E-64 increased the time to first oviposition, inter-egg mass interval, and number of days to complete larval development. E-64-fed females mated to E-64-fed males produced fewer eggs. There was no statistically significant difference between E-64-fed and control insects for either adult mortality, larval mortality, pupal weight or egg hatch (from E-64-fed females).On a per-day basis, insects fed E-64-treated leaves consumed similar amounts of leaf tissue to the control insects but, because of their longer larval development time, they required more leaf tissue to complete their larval development. The observed differences in life history parameters would potentially translate into large differences in population growth. The value of protease inhibitors for resistance against multivoltine specialist insects is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.52

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Based on field cage studies,Frankliniella occidentalis(Pergande) successfully overwintered and reproduced during the winter months in North Carolina. A field survey for thrips vectors of tomato spotted wilt virus (TSWV) was conducted during the winter and spring of 1990–1991 and 1991–1992 in North Carolina. Plant, litter, and soil samples were collected from three geographically distinct regions in North Carolina. Plant samples included 51 wild host species and five winter crops. Three species of TSWV vectors,Frankliniella fusca(Hinds),F. occidentalis, and ThripstabaciLindeman, were collected from plant samples.F. fuscawas the most abundant TSWV vector in plant samples and was collected from 30 wild host species and five winter crops. FewF. occidentalisandT. tabaciwere collected from plant samples.T. tabaciwas the most abundant vector collected from litter samples, andF. occidentaliswas the second most abundant. Very few thrips were recovered from soil samples. Terebrantia thrips larvae were collected from 28 wild host species, five winter crops, and litter samples. In addition to TSWV vectors, 23 thrips species in the family Thripidae and 1 species in the family Merothripidae were collected from wild hosts, winter crops, or litter samples. The highest number of thrips species were observed in litter samples.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.58

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We proposed two improvements to the Logan model of temperature-dependent development. We first eliminated a redundant parameter (modification 1) then incorporated an intercept parameter (modification2), thereby resolving the inability of the original model to estimate a low-temperature developmental threshold. The three model versions were compared using temperature-dependent developmental rates in six insect species (a total of 11 life stages).The original model and modification 1 produced identical curves. In 10 of the 11 cases, modification2 had the highest r2and the least estimation bias.

ISSN:1754-5692    

DOI:10.1093/ee/24.1.68

出版商:Oxford University Press    

年代:1995

数据来源: OUP