摘要:

The effects of feeding on host plant tissue infected with a plant pathogenic virus on thrips survival, reproduction, and development was studied. Western flower thrips,Frankliniella occidentalis(Pergande), exposed through feeding as larvae to the impatiens necrotic spot virus (INSV, formerly tomato spotted wilt virus-impatiens serotype) had lowered survival and reproductive potential and slower development rate than did unexposed thrips under controlled environmental conditions. Virus-exposed thrips were 1.4 times as likely to die than unexposed thrips in a given day. The reproductive potential for the virus-exposed group was significantly lower, and preoviposition period was extended. Development time from second instar to adult was 15% longer for thrips exposed to virus-infected plant tissue as larvae compared with the development time for thrips not exposed to the virus.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1308

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The effects of within-plant variation in seed size ofRosa multifloraThunb. on adult size, emergence, and morphology of the seed-feeding torymid waspMegastigmus aculeatus nigroflavusHoffmeyer were investigated. Large seeds were proportionally the most heavily infested by the wasps, and seed size significantly affected body size of emerged adults. Success in emerging from the seed was not influenced by seed size. The static intraspecific allometry of wasps was determined. Three of nine measured characters (length of scape, length of pedicel, ocellocular distance) had a negative allometric relationship (i.e., slopes of<1.0) when log-transformed and plotted against thorax length; the remaining measurements were isometric.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1313

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The orange striped oakworm,Anisota senatoria(J. E. Smith), has caused widespread defoliation of urban oak (Quercus) species in southeastern Virginia. The hypothesis that consecutive years of late-season defoliation byA. senatoriawould cause a significant reduction inQuercusgrowth and vigor was tested from 1987 to 1990. LateseasonA. senatoriadefoliation had a significant impact onQuercusgrowth and vigor. Pin oak,Q. palustris(Muenchhausen), and willow oak,Q. phellosL., planted in fabric containers, had significant reduction in growth with increased defoliation. Starch content and tree vigor inQ. palustris, planted in the urban landscape, was significantly reduced with increased defoliation, and some tree mortality occurred.Quercus phelloswas a hardier species compared withQ. palustrisand was not significantly affected by consecutive late-season defoliation. In addition, data suggested thatQ. palustriswas affected more byA. senatorialate-season defoliation when trees were planted in stressed urban sites. These data have important implications forA. senatoriamanagement strategies. High populations that have the potential to cause 100% late-season defoliation during consecutive years should be controlled to prevent progressive decline in tree health.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1318

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Emergence times of deutogynes of the pear rust mite,Epitrimerus pyriNalepa, from overwintering sites on branches of pear,Pyrus communisL., were compared between laboratory-stored (constant 1°C)and field-wintered branches at 2–4-wk intervals over 20 wk. Until wk 16, which corresponded to 1 March, 1992, the mean time to 50% emergence of mites declined steadily and was not significantly different between the two groups of branches. After wk 16, the mean time to median emergence of mites from field-wintered branches continued to decline, but there was no further decline in the emergence time of mites from laboratory-stored branches, resulting in a significant difference between the two groups. This divergence of the emergence times of mites from laboratory-stored and field-wintered branches after wk 16 indicated that Reid-wintered mites had begun “post-diapause” development or reactivation after ≍ 1 March. Emergence rates of individual mites from branches held at 1°C for 20 wk were compared at seven constant temperatures: 5.3, 7.8, 10.6, 13.3, 15.5, 17.6, and 20.8°C. Weighted, least squares linear regression was used to describe the relationship between emergence rate and temperature (rate = −0.1008 + 0.0162[temp]) for prediction of emergence in the field.The base threshold temperature for emergence was 6.2°C, as determined by extrapolation of the regression line to thex-axis. The relationship predicted that median (50%) emergence of mites requires 62 ± 1 degree-days (±SE) above the base temperature. The degree-day model was validated using field phenology data collected at one and four sites in 1991 and 1992, respectively. Using a 6.0°C threshold temperature for emergence, and daily minimum-maximum air temperatures beginning 1 March, the model accurately (±2 d) predicted the 50% emergence point. This article discusses the use of the degree-day model to improve current pear rust mite management practices in British Columbia.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1325

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The life history of the cynipid gall wasp,Antistrophus silphii Gillette, leaves it vulnerable to mortality in spring fires in the habitat of its host plant,Silphium integrifoliumvar.laeveTorrey and Gray. This article examines the mortality of gall wasp larvae during a prescribed bum at the Konza Prairie Research Natural Area in the tallgrass prairie of northeast Kansas. The three goals of the study were to determine (1) ifA: silphiigalls are most frequently found on the tallestS. integrifoliumshoots, (2) if there is a relationship between growing season gall height and overwinter lodging, and (3) if gall wasps can survive fire at the heights at which they are found after overwinter lodging. A 1988 survey found that galls were relatively rare on short shoots (140 cm), suggesting that gall wasps avoided short shoots but that gall placement did not maximize gall height. A 1992 survey found that growing season gall height was not related to overwinter lodging of galled shoots, indicating that any gall wasp shoot selection patterns affecting later gall height were disrupted by winter lodging. Gall wasps placed at post-overwinter lodging heights were unable to survive an experimental fire, but a few gall wasps survived when placed above the range of naturally-occurring gall heights.A. silphiiand other species with similar life histories must re-establish after fire by immigration, with subsequent population levels affected by indirect effects of fire on host-plant quality.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1333

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The factors having an impact on the survival of the F2seasonal generation ofHelicoverpa zea(Boddie) pupae in southwestern Arkansas field corn were identified and quantified. Last instar (fifth or sixth instar) field-collected com earworm larvae (480 per yr) were allowed to pupate in fields under four treatments designed to provide three levels of natural enemy exclusion. Mortality of these pupae and samples of feral pupae were determined and mortality factors were identified. Recovery of exuviae and remains from placed pupae were excellent (94 and 96% in 1990 and 1991, respectively). Moths emerged from the vast majority of test pupae (82.3 and 93.9% in 1990 and 1991, respectively). The exclusion treatments had no effect on the incidence of mortality in either year. Mortality was higher in 1990 (11.7%) than in 1991 (1.9%) because of the collapse of emergence tunnels prior to or during moth emergence. The increased incidence of collapse may have been caused by a significantly lower clay content (7.03%) in 1990 than in 1991 (16.4%). Observed biotic mortality was extremely low (2.1% and<1% in 1990 and 1991, respectively) in spite of a rich predator fauna as identified from pitfall traps. The large number of earworm larvae surviving to pupation following larval development in the ear of field corn, combined with the observed low mortality rates, suggests that a large number of moths would emerge from each hectare of corn at a time when other crops, particularly cotton, are attractive for oviposition. Enhancement of pupal mortality in ear-stage corn by cultural or chemical means is impractical or impossible, thus providing support for implementation of a biological control program that targetsH. zeapupae.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1338

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Reproductive phases, fecundity, and adult longevity of the squash bug,Anasa tristis(De Geer), were determined under laboratory conditions at a constant temperature of 26.7°C for five cucurbit hosts. Squash bugs on muskmelon,Cucumis meloL. ‘Hales Best #36’, had the longest premating phase. The preoviposition phase was shorter and the oviposition phase was longer on two cultivars ofCucurbita pepoL., yellow straightneck ‘Hyrific’ squash and ‘Jack O'Lantern’ pumpkin, than on watermelon,Citrullus lanatus(Thunberg) Matsumura and Nakai ‘Crimson Sweet’, and muskmelon. Females had the longest postoviposition phase on watermelon. The highest fecundity was observed on pumpkin seedlings. Host type did not affect egg mass size, egg hatch, percent hatch, or egg development. Higher percentages of egg masses were oviposited on the abaxial leaf surface than other plant locations on all hosts. Male squash bugs lived longer on pumpkin, squash, and watermelon than on muskmelon and cucumber,Cucumis sativusL. ‘Poinsett’, whereas females lived longer on pumpkin than on squash, muskmelon, and cucumber. Males lived longer than females on pumpkin and squash. The different host effects on reproduction, fecundity, and longevity indicate that host type is important when developing control strategies for the squash bug.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1344

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We determined whether early-season defoliation of range grasses affected the subsequent suitability of these plants for the Russian wheat aphid,Diuraphis noxia(Mordvilko). Grazing was simulated by clipping six grass species in northern Utah in April 1992. Aphid population growth was higher on clipped plants than on control plants, especially during theoversummeringperiod when aphids may rely on range grasses as alternate hosts. Aphids suffered complete mortality on 28% of control plants during this period but failed to establish themselves on only 2% of clipped plants. Defoliation increased plant nitrogen and water content, and differences in total nitrogen between clipped and control plants were positively correlated with differences in aphid density. Spring grazing may generally increase the susceptibility of grasses toD. noxia; an exception to this pattern was Indian ricegrass, which responds to defoliation by greater reproduction instead of rapid vegetative growth.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1349

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Concentrations of Cd, Cu, Fe, and Zn were measured in queens of fourBombusspp. and onePsityrussp. collected in the same area. The degree to which their concentrations in the various species reflected metal pollution levels in the area was assessed. Concentrations were the lowest for Cd, intermediate for Cu, and highest for Fe and Zn. No marked variation in concentrations of any of the metals was found among theBombusspp. Fe concentrations inPsityrussp. were significantly lower than those inBombus. Concentrations ranges within species were higher for Cd than for the essential metals.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1355

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Mortality of overwintering larvae of the wheat stem sawfly,Cephus cinctusNorton, was 92–93% in stubble exposed on the soil surface by tillage. Some larval mortality also occurred during April and May even though lethal low temperatures did not occur. There was 91-100% survival of larvae in untilled stubble. Field-collected larvae supercooled to −24.3°C in the laboratory. Larval mortality occurred before the supercooling point was reached. Fifty percent mortality occurred after 3 h at −22°C and 4–8 h at −20°C. There was no seasonal variation in larval resistance to freezing. Supercooling points were not significantly affected by plant material in larval guts.

ISSN:1754-5692    

DOI:10.1093/ee/22.6.1358

出版商:Oxford University Press    

年代:1993

数据来源: OUP