摘要:

The seasonal and geographic distribution of X-diseasedParaphlepsius irroratus(Say)was studied in south, central, and northwest Michigan in 1988 and 1989 using a DNA probe. C6c, a fragment of pWXl derived from infectedColladonus montanus(Van Duzee), detected eastern X-disease in diseasedP. irroratus. Maximum numbers of infected leafhoppers were detected at the beginning of the emergence of each generation in early June and in late September. In early summer the percentage of X-diseased leafhoppers at the various sites ranged from 12.2 to 43.3%, and in the late season from 3.3 to 36.4%. The X-diseased leafhoppers occurred only in south and central Michigan.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.81

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Head capsule widths of 10,677 larvae of the gypsy moth,Lymantria disparL., from different populations in Quebec were measured and compared with those observed in Massachusetts 90 yr ago. Mean head capsule widths for each of the six instars were almost identical to those observed 90 yr earlier. Larval growth ratios decreased with molt number in all populations studied. This disagrees with Dyar's hypothesis, which proposes a geometrical head capsule growth in Lepidoptera. Populations that showed the greatest departures from Dyar's hypothesis suffered the highest levels of natural mortality. Parasitism and NPV infection are suggested as stressing factors that could have modified gypsy moth larval growth.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.89

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The effects of herbivory by the Mormon cricket,Anabrus simplexHaldeman (Orthoptera:Tettlgoniidae), and removal of sagebrush(Artemisia tridentataNutt.) on understory plant biomass production and cover were determined. Averaged over a 3-yr period, 50–75% removal of sagebrush resulted in an ≍20% increase in summer understory biomass production; understory plant cover was not affected by sagebrush removal. Mormon crickets, at densities of four and eight crickets per square meter during a 5-wk period, did not significantly affect understory plant biomass production but did reduce forb and total vegetative cover. Mormon cricket herbivory and sagebrush removal were independent with respect to their effects on understory vegetation. Furthermore, the incomplete removal of sagebrush did not affect the feeding ecology of Mormon crickets. Analysis of cricket crop contents suggested that sagebrush was fed upon predominantly; there was little dietary overlap between crickets and cattle. As long as some sagebrush is left intact (e.g., 25%), sagebrush control programs are unlikely to influence Mormon cricket diet selection or damage potential. Cover estimates, which are commonly used by ranchers and rangeland managers to estimate forage availability, provide deceptive assessments of cricket effects, ultimately perhaps leading to an undeserved reputation as a rangeland pest.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.94

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A greenhouse experiment was designed to evaluate a series of forage legume seedlings in the cotyledon stage for susceptibility to seeding damage from adultSitona hispidulus(F.). Seedlings of a range of cultivars of white clover,Trifolium repens;alfalfa,Medicago sativa;red clover,Trifolium pratense; Lotusspp.; and crown vetch,Coronilla varia,were transplanted in the cotyledon stage into trays in a complete randomized block design. Adult weevils were added at a rate of one weevil per seedling. Feeding preferences of the weevils were assessed by visually estimating percentage defoliation of the seedlings 3 and 6–7 d later. A further experiment using cotyledon leaf discs randomly threaded onto an entomological pin further investigated weevil feeding preferences. Two similar whole seedling experiments and the leaf disc experiment indicated that white clover ‘Ladino’ was the most preferred species of the legume seedlings offered, followed by alfalfa ‘WL 318’ and two red clover cultivars, ‘Kura’ and ‘Arlington’.Lotusspp. and crown vetch were preferred least. Defoliation levels ranged from 32 to 93% after 6 to 7 d in the whole seedling experiments and from 11 to 46% after 4h in the leaf-disc experiment. Damage assessments of the unifoliate or first true leaflets indicated an order of feeding preference similar to that found for cotyledon leaves. Defoliation levels of whole seedlings were not linearly correlated with seedling size or fresh weight, and this, supported by the results with the leaf discs, suggest that in the whole seedling experiments, plant size did not determine the levels of defoliation.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.103

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The effects of the patterns of within-stage survival and feeding rates on modeling foliage consumption were evaluated with a computer simulation model for the immature stages of Mexican bean beetle,Epilachna varivestisMulsant, on dry beans,Phaseolus vulgarisL. Feeding and survival rates were simulated as linear and nonlinear functions of degree-days. Constant and linear age-specific feeding rates within a developmental stage were found to result in different levels of daily consumption. Different types of survival within a developmental stage also greatly altered the amount of daily and total consumption. More importantly, the interaction between survival and feeding patterns resulted in a difference of up to 40.04% of total stage foliage consumption. These results suggest the importance of incorporating within-stage feeding and survival patterns in insect simulation models.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.107

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Sex pheromone traps and visual observation stake counts were used to investigate daily and generational flight activity, and relative efficiency of pheromone traps for the day-flying moth,Harrisina brilliansBarnes&McDunnough. A total of 19 intraday studies were conducted during the second and third annual moth flights of 1986 and 1987 in a central California grape vineyard. Visual counts and pheromone trap data indicated that daily peak flight occurred near 0800 hours.H. brilliansadult males were most active in the early morning, with substantially fewer moths detected after midmorning. From 0600 to 1000 hours,>90% of the moths observed in the stake count zones were males. For the remainder of the day, a greater portion of flyingH. brilliansmoths were represented by females. Pheromone trap count curves were frequently bimodal. This pattern of bimodality may result from competition between synthetic lures and female moths emitting pheromones.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.112

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Field studies were conducted in central Texas in 1988 and 1989 to determine the effect of oviposition on overwintering survival of the boll weevil,Anthonomus grandis grandisBoheman. Weevils were reared from infested cotton bolls in field cages. At eclosion, adults were paired with mates and provided artificial diet for 36 d before they were installed in overwintering cages without food. The earliest oviposition occurred between 6 and 10 d after eclosion; increasing numbers of females began to oviposit thereafter. Females that laid any eggs at all during the 36-d feeding period died within 7 wk in the absence of food. Females that never laid eggs during the feeding period had high survival until the following spring. Overwintering survival of males was unrelated to their mate's fecundity. Our results suggest that even limited reproductive output by females imposes a substantial cost to subsequent overwintering survival in this central Texas population.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.117

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Forty-five plant species were surveyed for thrips during the winter and spring in Georgia. The western flower thrips,Frankliniella occidentalis(Pergande) (Thysanoptera: Thripidae), was collected from 44 plant species, and the tobacco thrips,Frankliniella fusca(Hinds), was collected from 25 plant species. Adults of both species were 60–100% female in most samples. Thrips larvae were collected from 37 plant species, but were relatively uncommon until mid-March. Western flower thrips and tobacco thrips were most abundant during the spring onTrifoliumspp. and volunteer peanut,Arachis hypogaeaL., respectively. Volunteer peanut was intensively sampled for thrips during the fall and spring. Adults were 60–95% tobacco thrips in most samples, with western flower thrips comprising the remainder. Thrips larvae were collected in all samples, but were more numerous during the spring. Adult tobacco thrips were predominantly brachypterous during the late fall and early spring, suggesting that some populations of tobacco thrips overwinter in old peanut fields. Brachypterous adults were rarely observed on peanut transplanted during late March into an old pearl millet,Pennisetum americanum(L.), field, but were common on peanut transplanted into an adjacent old peanut field. The potential of tobacco thrips, western flower thrips, and their plant hosts as winter reservoirs for tomato spotted wilt virus (TSWV) is discussed. Destruction of overwintering thrips, volunteer crops, and winter annual weeds in cultivated fields is suggested as a potential strategy for TSWV management.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.121

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Conidial discharge by a 1984 Japanese isolate ofEntomophaga maimaigaHumber, Shimazu&Soper infecting gypsy moth,Lymantria dispar(L.), larvae was investigated under field conditions. On an hourly basis, levels of conidia discharged were correlated with relative humidity (RH) for the previous 2 h and with leaf wetness for the previous 3 h. Greater than 90% of cadavers discharged maximum numbers of conidia between 2000 and 0800. Increased hours of RH ≥70 or ≥90% after larval death and before sporulation began resulted in increased numbers of conidia released during the first day of sporulation. One-day-old cadavers usually sporulated within an average of 1.5–2.2 d of being placed in the field and 71.6% of cadavers produced conidia for ≤2 d during the average of 5.4 d they were monitored. Cadavers of larvae infected withE. maimaigademonstrated the ability to sporulate, cease sporulation, and later sporulate again; however, the numbers of conidia discharged after conidial discharge resumed were much lower. Of 40 larvae infected withE. maimaigathat produced only resting spores after death, 50% persisted on tree trunks for only 2 d, although 19.7% still remained attached to tree trunks after 9 d.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.129

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The effect of competition among same-aged larvae of the vegetable leafminerLiriomyza sativaeBlanchard was investigated in laboratory studies over a range of densities from 0.1 to 2.9 larvae per cm2of lima bean primary leaf area. Both exploitative and interference competition (cannibalism) occurred among larvae. Cannibalism was observed primarily between first or second instal's, and was not density-dependent at<1.0 first instal's per cm2. Percentage larval survival (y) was ∼90% at densities of<1.0 larvae per cm2but declined significantly as the density of first instal's(x)increased(y= −20.0x + 115.6, t = −9.0, df = 47, P<0.0001, r2= 0.64). Among leaves with densities<1.0 first instal's per em, there was no significant relationship between larval weight (yin micrograms) and density (x) (t= −1.4, df = 194,P= 0.18), although the relationship was significant when leaves across the entire range of densities were included (y= −108.5x + 702.3,t= −19.1, df = 1603, P<0.0001). Exploitative competition occurred between third instal's at higher densities. Larval weights varied considerably among individuals utilizing the same leaf and density explained only 18% of the variability in weight. Larvae from leaves with a mean first-instal' density of 2.8 larvae per cm2weighed, on the average, 37% less than those emerging from leaves with 0.3 larvae per cm2. Percentage pupal survival (y) decreased significantly with increasing density (x) (y= −10.9x+ 102.5,t= −4.3, df = 33,P= 0.0001,r2= 0.37). The area of individual leaf mines measured 0.99 ± 0.12 cm2($\bar x$± SEM). There were no apparent seasonal trends in area of leaf mines.

ISSN:1754-5692    

DOI:10.1093/ee/21.1.136

出版商:Oxford University Press    

年代:1992

数据来源: OUP