摘要:

In a greenhouse experiment we documented the effects of low, medium, and high nitrogen in cotton on development and honeydew production by the whitefly,Bemisia argentifoliiBellows and Perring. Nitrogen status of cotton plants was manipulated by irrigation with 0.5, 2.5, or 5.0 mmol/liter nitrogen fertilizers. Although the fertilization treatments produced large differences in plant growth, subtle differences were found in whitefly development. No differences among treatments were found in stage-specific survival or the time whiteflies spent in each stadium. Time to adult emergence by whiteflies increased with decreasing nitrogen fertilization. Although early-instar whiteflies on high nitrogen plants initiated the production of honeydew droplets before whiteflies on medium and low nitrogen treatments, they subsequently generated fewer droplets through 24 h periods.

DOI:10.1093/ee/23.2.316

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The effect of age at first mating on the reproductive potential of the fall armyworm,Spodoptera frugiperda(J. E. Smith), was studied in the laboratory. The age of females at first mating affected the number of eggs laid, percentage of eggs hatching, number of viable larvae, and longevity. Extending female virginity to an advanced age increased longevity. The age of males at first mating had relatively little influence on the reproductive potential of females. However, the age of the male and female at first mating interacted to affect the reproductive potential of respective pairs. The number of spermatophores harbored by females affected percent daily and total eggs hatching, number of eggs laid, and the number of viable larvae produced. The number of spermatophores harbored by females had no effect on moth longevity.

DOI:10.1093/ee/23.2.322

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The aphid-resistant wheat lines PI137739 and PI262660, along with the susceptible wheat varieties ‘Bliss’ and ‘Stephens’, and the resistant oat variety ‘Border’, were infected with five barley yellow dwarf virus (BYDV) isolates (MAV, PAV, RMV, RPV, SGV) to test the influence of barley yellow dwarf virus (BYDV) infection on the performance (survival and fecundity) of the Russian wheat aphid,Diuraphis noxia(Mordvilko). Antibiosis in lines PIl37739 and PI262660 could not be detected statistically when the uninfected plants were analyzed separately. When data from only BYDV-infected plants were analyzed, Russian wheat aphid performance was significantly less on both PI137739 and PI262660 than on the susceptible varieties, indicating that plant stress influences expression of Russian wheat aphid antibiosis. Relative to uninfected controls, BYDV infection did not affect Russian wheat aphid performance on either susceptible wheat variety or the resistant line PI137739. In the resistant line PI262660, PAV, RPV, and SGV infection significantly reduced Russian wheat aphid performance. By contrast, PAV infection significantly increased aphid performance on ‘Border’ oats, but it was still far below performance on any other plant-virus combination. These results suggest that BYDV infection does influence Russian wheat aphid survival or fecundity, or both, on certain hosts even though the aphid is not a vector of the virus isolates used in this study.

DOI:10.1093/ee/23.2.326

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Preliminary field evaluation of 43 rice anther culture lines in 1990 for resistance to the rice water weevil,Lissorhoptrus oryzophilusKuschel, identified several lines with potential for tolerance. The seven most promising lines (952836, 953508, 953509, 953510, 953511, 953527, and 953541) were evaluated for tolerance in 1991 and 1992. The parameters used to assess tolerance included rice water weevil larval population, root pruning damage, plant height, and grain yield. Significant differences were found among the lines tested with regard to rice water weevil larval populations, root damage ratings, plant height, and grain yields. The comparison of insecticide treated and untreated plots indicated that lines 952836 and 953527 exhibited moderate levels of tolerance to the rice water weevil. Tolerance in the lines was expressed, in part, as the ability to recover from root pruning damage and to produce high grain yields.

DOI:10.1093/ee/23.2.331

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Flowers of 37 wild plant species located in North Florida were sampled at periodic intervals for selected thrips (Thysanoptera) species. Samples were collected from wooded areas adjacent to two tomato production fields over an 18-mo period beginning March 1989. Of the 2,583 thrips specimens collected, 78% were adults. Adult counts peaked in May at both sites during 1989 and 1990. The genusFrankliniellaaccounted for 87% of the adult thrips collected. The most common species collected wasF. tritici(Fitch) followed byF. bispinosa(Morgan),F. occidentalis(Pergande), andF. fusca(Hinds). Species composition varied by sampled month.Frankliniella triticiwas the most abundant species in March, May, and August;F. bispinosain June and July; andF. occidentalisin February and April. The distribution of thrips that vector tomato spotted wilt virus was similar to that of non vectors in Rowers of wild hosts. Thrips were detected on 31 of the 37 wild plant species surveyed with 61% of all thrips collected inhabiting six plant species.Frankliniella occidentalisandF. triticiused a major proportion of the available wild plant species earlier in the season thanF. bispinosaandF. fusca.AllFrankliniellaspecies exhibited a wide host range in April and May.

DOI:10.1093/ee/23.2.337

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

This research was designed to determine corn earworm,Helicoverpa zea(Boddie), biology in irrigated food corn and identify beneficial insects and diseases associated with them. We were interested in determining the period of oviposition and feeding by corn earworms to understand when corn is most vulnerable to feeding damage from larvae for designing pest management tactics. These data were collected on corn during pollination and kernel development. Oviposition began with appearance of the first silks but did not peak until late July after silks were dry and continued until late in the dough growth stage. Most eggs were laid on the distal third of silks. After eclosion, larvae quickly moved to the basal third of silks usually under the husk. Larvae began feeding on kernels as third instars appeared. They penetrated 9 and 15 cm into the ear, respectively, in each of the 2 yr. Deep penetration of the ear occurred in August as kernels hardened. Larvae could not eat these hard kernels, therefore, they simply took bites out of many kernels (nipped), which lowers the quality of corn for food processing. Only 1% of the corn earworms were parasitized or infected with disease organisms.

DOI:10.1093/ee/23.2.343

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Aphids and their parasitoids were sampled in seven and eight commercial rapeseed fields in 1990 and 1991, respectively. Whole-plant sampling was used for aphids during the budding plant stage. Sweep-net sampling was used for aphids and their parasitoids during the flowering and ripening plant stages. Three species of aphids, turnip aphid,Lipaphis erysimi(Kaltenbach); green peach aphid,Myzus persicae(Sulzer); and cabbage aphid,Brevicoryne brassicae(L.), were collected. The turnip aphid was the most abundant species collected in 1990 and 1991, 99.9 and 86.8%, respectively. Turnip aphid populations peaked (80%) most frequently during the flowering stage, and visual observations taken of feeding damage noted stunted growth, reduced pod formation, and uneven stand maturity. Turnip aphids were parasitized by the wasp parasitoid,Diaeretiella rapae(M'Intosh) (Hymenoptera: Aphidiidae). In 1990, the totalD. rapaedensity was 883 wasps per 50 sweeps and this was 24 times higher than the total 1991 density of 37 wasps per 50 sweeps. Aphid infestations were observed to cause substantial damage to rapeseed stands in 1990. However, the lack of quantitative yield-loss data precludes the effective integration of natural and chemical control strategies on rapeseed.

DOI:10.1093/ee/23.2.349

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Six apple maggot,Rhagoletis pomonella(Walsh), trap designs were evaluated in both managed and abandoned orchards. On the basis of trap efficacy, a protocol was developed for a control strategy using the Ladd trap (red hemispheres on a yellow rectangle) baited with apple volatiles, for which captures on red were consistently greater than on yellow. In another study, washed bacterial cells (media washed from the culture, and cells suspended in distilled water) ofEnterobacter agglomeransremoved from adult apple maggot and placed onto Ladd traps had significantly greater captures than did traps with washed cells from a standard culture or with ammonium acetate. The control strategy using the same protocol was also evaluated using the Ladd trap baited with apple volatiles and washed bacterial cells. There was a significant increase in the capture of gravid females on yellow surfaces and no detectable injury from the apple maggot at harvest. Fruit treated weekly in the field with an antibiotic mixture of streptomycin and rifampicin significantly reduced fruit injury indicating that the bacterium may serve some essential nutritional or biological need.

DOI:10.1093/ee/23.2.354

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Gypsy moth,Lymantria disparL., oviposition and pupalsurvivalwere examined within mixed pine-hardwood stands located in the Virginia and North Carolina coastal plain and the North Carolina piedmont. Where burlap bands were not present as barriers to larval dispersal, the percentage of loblolly pine with gypsy moth egg masses present was significantly greater than expected if oviposition occurred randomly. The loblolly pine and oak components of the forests also had more total egg masses per tree compared with the other tree genera or species. However, when adjusted for tree size, egg mass density was generally similar among tree groups within an infestation. Tree size (dbh) was positively correlated with the number of egg masses present on a tree. Pupal predation, measured using freeze-dried pupae, was significantly higher over the 5-d sample period for (1) females versus males, (2) pupae placed at 0 m on the tree bole versus at 2 m, and (3) pupae placed on oak versus pine. The differential predation on oak versus pine appears to be the result of heavier vertebrate predation of the pupae placed on oak. The high rate of pupal removal, beginning the first night of exposure, from all locations suggests that predators will not have to learn to accept gypsy moth in their diets. The higher survival of pupae on pine is suggested to be one of the factors influencing the high egg-mass density on pine. Implications of these results for gypsy moth population dynamics in southern pine-hardwood forests are discussed.

DOI:10.1093/ee/23.2.360

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Immature maize weevils,Sitophilus zeamaisMotschulsky, in corn were exposed toAnisopteromalus calandrae(Howard) alone,Choetospila elegansWestwood alone, or a combination of both species.Anisopteromalus calandraewas much more efficient at parasitizing immature maize weevils in corn than wasC. elegans.The combination ofA. calandraeplusC. eleganshad similar effects asA. calandraealone on total maize weevil mortality for equal numbers of parasitoids. Under interspecific competition, the emergence ofC. elegansprogeny and their sex ratio (percentage female) were significantly reduced in the presence ofA. calandrae, butA. calandraewas not affected substantially byC. elegans.

DOI:10.1093/ee/23.2.367

出版商:Oxford University Press    

年代:1994

数据来源: OUP