摘要:

Behavior of third-instarHeliothis virescens(F.) was observed on six genetically modified cotton lines (transgenic) expressing the δ-endotoxins produced by altered genes fromBacillus thuringiensisBerliner var.kurstaki(strains HD1 or HD73). On transgenic lines the percentage of time larvae spent feeding was reduced to about 18% and resting increased to about 60% compared with 50 and 33%, respectively, for the nontransgenic control, ‘Coker 312’. Larvae on some of the transgenic lines spun-down (i.e., dropped off the plant on a silken thread) and abandoned plants more frequently than larvae on ‘Coker 312’. Reduced feeding and increased plant abandonment on some transgenic lines may be due, in part, to midgut paralysis and/or repellency of the δ5-endotoxin. Two cage experiments (one greenhouse and one field), were conducted to evaluate H. virescens survival and plant damage on the transgenic lines. Larval survival was<2% for all transgenic lines. Some transgenic lines had no larvae surviving the 10-d confinement. Percentage of damaged flower buds and bolls on all the transgenic lines were less than on ‘Coker 312’. Some transgenic lines had no damaged flower buds or bolls compared with 64 and 74% damaged, respectively, for ‘Coker 312’. Another greenhouse experiment was conducted where transgenic lines and nonexpressing ‘Coker 312’ controls were inoculated with 100 eggs ofHelicoverpa zea(Boddie). Percentage of damaged flower buds and bolls was 2 and 6%, respectively, on a transgenic line expressing the HD73 endotoxin, compared with 54 and 55%, respectively, for the control. These data indicate that transgenic cottons offer excellent potential for suppression ofH. virescensandH. zeadamage and for reduction of insect control costs in production agriculture.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.1

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Sampling statistics were determined for cysts of the margarodidsEumargarodes laingiJakubski andPromargarodesspp. in sugarcane crops in southern Queensland, Australia. The Poisson distribution, Iwao's regression model, and Taylor's power law were used to determine the relationship between mean and variance of counts of both types of margarodids from sugarcane crops of different ages. All models indicated that the cysts were aggregated in distribution. Taylor's power law generally gave better or equivalent fits to the population dispersion parameters than did Iwao's regression model. Relationships to determine sample sizes for fixed levels of precision and fixed-precision-level stop lines for sequential sampling were developed for each margarodid genus. There were functional relationships between the variance and mean of untransformed population counts for all margarodids and crop ages, and the suitability of three transformation functions is assessed.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.10

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Nonspecific e16r2e banding patterns of the sweetpotato whitefly,Bemisia tabaci(Gennadius), were analyzed by native polyacrylamide gel electrophoresis. Banding patterns of>300B. tabaciadults from 30 populations in Hawaii matched the B type esterase banding pattern produced by the B biotype standard from Arizona. Banding patterns representative of otherB. tabacibiotypes were not found. Zucchini,Cucurbita pepoL., ‘Ambassador’, plants colonized by field-collected individuals from seven populations developed symptoms of squash silverleaf disorder. Reproducing populations of the B biotype were observed on several crops not previously reported as hosts in Hawaii: papaya, manoa lettuce, taro,Brassicaspp., and plumeria. The distribution and relative proportions ofB. tabaciand the greenhouse whitefly,Trialeurodes vaporariorum(Westwood), present in Hawaii vegetable crops was determined using vacuum samples from grower fields.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.16

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Dispersion indices were calculated forTetranychus kanzawaiKishida in groves of mulberry,Morns alba(L.), in Taiwan. These indices indicated a clumped distribution for the surveyed population range ofT. kanzawai: 0.53–96.5 mites per leaf. However, theX2goodness-of-fit test generally rejected the negative binomial model among trees, but accepted it within trees. The level of aggregation varied with the population density ofT. kanzawaiand among mulberry groves. The dispersal of spider mites is discussed as a factor affecting this parameter. Optimal sample size is estimated for various densities ofT. kanzawaiand error margins on the assumption of Taylor's power law and mean crowding-mean regression.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.21

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The correlation of various preseason field measurements with subsequent defoliation by the gypsy moth,Lymantria dispar(L.), was examined from a series of forest stands in central Pennsylvania. These measurements included preseason egg-mass density, density of old egg masses (residual egg masses from previous generations), fecundity, number of larvae hatching per mass, egg-mass length, and host-tree basal area. Egg density (product of fecundity and egg-mass density) was the best single variable for predicting defoliation. The product of egg-mass density and mean egg-mass length provided predictions of defoliation nearly as well as egg density, reflecting the previously observed linear relationship between egg-mass length and fecundity. The addition of the ratio of new-old egg masses to the model significantly increased the model fit. Parameters of these and other parameters in linear and nonlinear (Weibull) models are provided. These results indicate that recording one or two additional field measurements (egg-mass length or counts of old egg masses) increases the precision in the prediction of defoliation when densities range from 100 to 10,000 egg masses per acre (250 to 25,000 egg massesper ha).

ISSN:1754-5692    

DOI:10.1093/ee/22.1.26

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Insect detection and mean trap catch efficiency of two types of commercial probe traps, the Storgard WB Probe II (WB II) and Grain Guard (GG), were compared by sampling live beetles in the top ≤28cm of shelled corn stored in three round bins and two flat units. Unbaited WB II and GG traps were paired, and number of trap pairs among the five facilities ranged from 8 to 20. Insects were trapped between July and September 1990, and the trapping duration was 7 or 14 d (only in one flat unit). Adults of 13 species were detected by WB II traps, whereas 11 species were detected by GG traps. In general, insect species were more frequently detected and trap catches were higher in WB II traps than in GG traps. However, differences in insect detection and mean trap catch between the trap types were small. A double logarithmic model satisfactorily described (R2= 83%) the nonlinear statistical relationship between proportion of traps with adults and mean trap catches for both trap types. The progressively slower increase in proportion of traps with insects with increasing mean trap catches for both trap types can be explained by a purely probabilistic increase in the chance of a trap having more than one insect. This doublelogarithmic model is valuable for predicting mean trap catches, solely based on proportion of traps with insects. When validated with two independent data sets, obtained by sampling insects in shelled corn with WB II traps and in stored barley with GG traps, the predicted mean trap catches explained ≥84% of the variation in observed mean trap catches.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.33

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Cotton plants,Gossypiumspp., were treated with long-lasting dispensers containing gossyplure, the sex pheromone of the pink bollworm,Pectinophora gossypiella(Saunders). Samples of air from 0.15 m above ground level and from above the tops of plants were pulled through adsorbent cartridges during day and night periods (0600–1800 and 1800–0600 hours [PST], respectively) and analyzed by gas chromatography for gossyplure content. The gossyplure was applied in Shin-Etsu rope or bag dispensers to 5-ha areas at rates of 86.8 or 71.6 g Al/ha, respectively, at the pin-square (first-Rower bud) stage of plant development. Air samples were taken during 3-d periods beginning 20, 40, 63, and 84 d after application. Ten Delta traps, each baited with 1 mg of gossyplure, were used to capture males in each treated area and an untreated control field. Eight samples of 200 bolls per area were collected weekly from treated and control areas during August and September and incubated for 2 wk before counts of pink bollworm were made. Temperatures and wind speed were recorded at 0.3 and 1.8 m above ground level in the cotton field. Temperatures and wind speeds were similar at 0.3 and 1.8 m above ground level when the cotton plants were small, but as the plants grew, temperatures were 4°C lower and wind speeds were reduced to<0.5 m/s at 0.3 m. Emission of gossyplure from rope dispensers was greatest following application and then declined, whereas the emission from bag dispensers increased slightly throughout the test period. Trap catch of males in both treated areas was reduced 99% compared with the control area during 60 d following application. No pink bollworm were found in 1,600 bolls collected from each treated area compared with 13 pink bollworm collected from the control area. Aerial concentrations of gossyplure followed similar patterns in rope and bag fields during canopy formation. Daytime and nighttime aerial concentrations of gossyplure at 0.15 m increased significantly during the test, whereas concentrations at the tops of the plants changed little. These results show that the nighttime aerial concentrations in the mating arena of moths at the tops of the plants do not reRect the increasing concentrations at 0.15 m as obtained with the dispensers applied at pin-square.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.43

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

During an infestation of Mediterranean fruit fly,Ceratitis capitata(Wiedemann), in northern California, malathion-Staley's bait was sprayed as an eradicant. As a part of a study on the effect of this spray on nontarget organisms,Aleyrodes spiraeoidesQuaintance and two of its chalcidoid parasitoids,Euderomphale flavimedia(Howard) andEncarsia peltata(Cockerell), were chosen as index species. Simulated aerial bait sprays were used to test effects of the spray on foliage on the longevity, production of progeny, and presence on foliage of test insects. The sedentary feeding behavior and preference for the undersides of leaves protected the whitefly from severe intoxication. The more active parasitoids were highly susceptible. Despite similar adult susceptibility, Encarsia was significantly more successful thanEuderomphalein parasitizing whiteflies. Bait-sprayed foliage was relatively free of adult parasitoids; test results suggested some degree of active avoidance or enhanced dispersal by the wasps in addition to mortality because of bait. No significant increase or decrease in numbers ofAleyrodeswas observed over the short term despite significant reductions in activities of its parasitoids.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.49

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Leaf abscission caused by herbivores is well documented, yet the relationship between abscission and amount of damage required to initiate abscission is poorly known. This relationship was investigated in a southern Appalachian forest by mechanically damaging (0,25,50, and 75% area removed) leaves from red maple,Acer rubrumL., flowering dogwood,Comus floridaL., tuliptree,Liriodendron tulipiferaL., and chestnut oak,Quercus prinusL., and monitoring leaf survival. Leaf survival was negatively related to percentage leaf area removed in 1985 and 1986. Timing of leaf abscission was not significantly different among tree species in 1985. In 1986, there were, however, significant differences among species, which coincided with a severe drought. Damage by herbivorous insects after treatment was measured in 1986 and differed significantly among treatment levels in tuliptree only. Despite significant effects of treatment damage on leaf survival, abscission of damaged leaves occurred at the beginning of normal autumn senescence and leaf fall (except tuliptree in 1986). These results are interpreted with respect to insect-mediated litterfall and its potential influence on the activities of forest floor decomposer organisms.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.57

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The southern pine bark beetle guild [Dendroctonus frontalisZimmermann,D. terebrans(Olivier),Ips calligraphus(Germar),I. grandicollis(Eichhoff), andI. avulsus(Eichhoff)] uses disturbed hosts as habitat for establishment of within-tree populations. We examined the process of colonization of disturbed hosts. Using a procedure designed to emulate effects of a lightning strike, pines were severely disturbed. Response was characterized by measuring beetle populations that (1) arrived at the trees and (2) successfully attacked the trees. Establishment of within-tree populations was characterized by measuring length of egg gallery excavated by attacking adults. The time delay between arrival and attack forD. frontalisandI. calligraphuswas also calculated. Attack densities of both species became asymptotic as arrival increased. The percentage of arriving beetles that attacked ranged from 9 to 41 forD. frontalisand from 8 to 59 forI. calligraphus. Numbers of beetles that arrived at the tree but did not attack ranged from 2.7 to 50.2 beetles per dm2forD. frontalisand from 0.2 to 10.0 beetles per dm2forI. calligraphus. MostD. frontalisandI. calligraphusattacked on the day they arrived. The delay between arrival and attack was longer forI. calligraphusthan forD. frontalis. Egg gallery excavated byD. frontalisincreased throughout the study. Eventually, theIpsspecies were excluded from the lower half of the bole. The low attack densities observed in this study illustrate the significance of disturbed trees in providing refuges for enzootic levels of bark beetles. The aggregation behavior of beetle populations colonizing disturbed hosts supported the contention that these trees serve as foci for initiation of infestations. Furthermore, in disturbed pines, small numbers of beetles were capable of overcoming host defense systems.

ISSN:1754-5692    

DOI:10.1093/ee/22.1.62

出版商:Oxford University Press    

年代:1993

数据来源: OUP