摘要:

A simulation model was developed to predict how long it would take a pest to adapt to two antibiotic, host-plant resistance factors if they were deployed sequentially, as a cultivar mixture, or combined in a single pyramided resistant cultivar. Results indicated that no single deployment strategy was most durable in all pest/cropping system combinations. When relative fitness of the insect pest on plants with both resistance factors was linearly related to the number of adaptive alleles that the insect possessed, sequential release of two cultivars with different single resistance factors or mixed planting of these two cultivars was expected to provide weaker but more durable resistance than pure plantings of a cultivar into which both resistance factors had been pyramided. If totally susceptible plants are grown adjacent to the pyramided cultivar in a ratio that causes the mean fitness of insects with no adaptive alleles to be equivalent to their mean fitness in the sequential-release plan, the durability of all three strategies is similar. If alleles for adaptation are recessive and epistasis is strong enough to make the two resistance factors largely redundant in plants possessing both factors, pyramided deployment of resistance factors is often expected to be much more durable than a sequential or mixed release. Durability of the pyramided cultivar is enhanced by adding some totally susceptible plants to the system. Structural linkage of the two insect loci would reduce durability of such a pyramided cultivar, but it would usually be more durable than sequential or mixed releases.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.1

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

In an attempt to determine what strategies of resistant germ plasm deployment would most successfully inhibit Hessian fly,Mayetiola destructor(Say), adaptation to wheat resistance factors while offering significant crop protection, a computer simulation model was developed to mimic ecological/genetic interactions between Hessian fly populations and resistant winter wheat. Durability of the following resistant germ plasm deployment strategies was examined: 1) sequential release of two pure cultivars, each with a single resistance factor, 2) release of a random spatial mixture of these two cultivars, 3) release of a pure cultivar in which both resistance factors were present in each plant (pyramided), and 4) modification of each of the above deployment strategies by addition of totally susceptible wheat to the system. Effects of temporal and spatial characteristics of the mixtures were also explored. Interpolating a pyramided resistant cultivar with some totally susceptible plants offers the highest relative durability in most cases, and is predicted to last>400 fly generations under some conditions.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.11

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

A genetic model describing the interaction between the wheat plant,Triticum aestivumL., and the Hessian fly,Mayetiola destructor(Say), is presented. The model is based on multiplicative interlocus interaction and gene-for-gene interaction between host and insect. It can be used to predict changes in allelic frequency in the insect and in the level of potential crop damage caused by deployment of host resistance genes, given genotypic fitnesses and initial allelic frequencies. Given reliable estimates of genetic parameters, the model can be used to make predictions where there are unequal genetic effects and frequencies and a much wider range of resistance-gene deployment patterns.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.24

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

The hymenopterous parasitePediobius foveolatus(Crawford) was highly susceptible toNosema epilachnaeBrooks, Hazard and Becnel andN. varivestisBrooks, Hazard and Becnel, two naturally occurring microsporidia of the Mexican bean beetle,Epilachna varivestisMulsant. After female parasites oviposited in late-instar larvae exposed previously to spores of each microsporidium as either early instar larvae or as late-instar larvae 24 h before parasite oviposition, progeny of the parasites were infected directly by the microsporidia and infection appeared to be systemic in nature. In heavily infected hosts, incidence of infection by both microsporidia in the parasites' progeny approached 100% and percentage mortality was also high. Mortality occurred primarily in the pupal stage and incidences of infection and mortality were directly related to degree of host infection or microsporidian virulence. Most infected adults were normal in appearance but some had malformed wings, greatly swollen abdomens, or both. Infection did not adversely affect the development period of emerging adults but adult longevity was significantly reduced. Adults were also susceptible to both microsporidia per os. Relatively few female parasites of the P generation that were infected withN. epilachnaewere capable of ovipositing in host larvae, and only one female transmitted the pathogen transovarially to some of her progeny. Female parasites, infected withN. varivestis, successfully transmitted the microsporidian transovarially to F6individuals at rates varying from 5.8 to 70.0%. Both microsporidia were also transmitted mechanically from diseased to healthy hosts during parasite oviposition.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.32

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

The principal sex pheromone ofFeltia jaculifera(Guenée) was identified as (Z)-11-hexadecenyl acetate by electrophysiology, chemical analysis, and behavioral tests. Field traps baited with 10–100 µg of this compound captured manyF. jaculiferamales, but incorporation of ca. 0.05% (Z)-7-dodecenyl acetate in the lure greatly increased numbers taken. Addition also of ca. 0.1% (Z)-9-tetradecenyl acetate gave a still stronger lure. Flight tunnel studies confirmed these compounds' synergistic action.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.40

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

The horn fly,Haematobia irritans(L.), overwinters by diapausing as a pharate adult within the puparium. In south-central Texas the flies enter diapause in October and November. The peak in production of diapausing pharates occurs during the first 2 weeks of November, when there is an optimal combination of pupa production and diapause induction. Adult flies emerge from diapause from late February to early May. Those entering diapause later tend to emerge slightly earlier relative to the total spring emergence pattern, indicating a more intense diapause development. There is a substantial mortality due to pupa parasites of the genusSpalangia.The wasps overwintered within puparia of the host and entered quiescence coincident with onset of diapause in the fly.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.44

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Population parameters of the green peach aphid (GPA),Myzus persicae(Sulzer), were compared on potatoes fertilized with different levels of nitrogen (N) (56, 84, 140, and 224 kg N/ha). Abundance of GPA was not significantly different among N treatments. The population growth rate of GPA increased with the level of N applied. However, the highest level of N (224 kg N/ha) reduced the rate of population growth. Populations grew more rapidly on potatoes fertilized with a split-applied intermediate N treatment (56 + 84 kg N/ha) than on potatoes fertilized with 56, 56 + 28, or 56 + 168 kg N/ha. Additionally, populations of GPA grew more rapidly when 224 kg N/ha was applied in one application than when applied in two applications. The rate of population growth was positively correlated with the concentration of free amino acids in leaves. The within-plant distribution of GPA was similar for all treatments. GPA were consistently more abundant on the lower leaves in each treatment. Population growth rates were greater on lower leaves than on other leaves in most N treatments. Population growth rates were negatively correlated with foliar concentrations of free amino acids within leaves of different vertical zones, but were positively correlated with foliar concentrations of nitrate N within leaves of different vertical zones. Also, population growth rates were positively correlated with the percentage of the total organic N pool composed of amino N within leaves of different vertical zones. Implications of variable host-plant nutritional quality in pest management are illustrated.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.49

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Periodic exposure of laboratory-rearedMusca domesticaL. pupae was used to study seasonal and diel activity patterns of pteromalid pupal parasites in poultry manure.Muscidifurax zaraptorKogan&Legner (July to October),M. raptor(Girault&Sanders (June to October), andSpalangia cameroniPerkins (May to November) were most commonly collected. Others includedS. nigroaeneaCurtis (July, September, November),S. endiusWalker (July), andNasonia vitripennis(Walker) (March, July). Exposure of pupae during a 12-h daytime or 12-h nighttime period indicated thatM. zaraptorand probablyS. cameroniwere primarily diurnal in their searching activity. Some nocturnal activity was noted forS. cameroni. Predation of pupae bySolenopsis maniosaWheeler appeared to be severe in peripheral surface manure areas during the summer. A treatment of extensive wet manure areas with dimethoate larvicide appeared to have a deleterious impact on parasite activity, particularlyM. zaraptorandM. raptor, in the summer of 1984.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.56

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Atmospheric CO2levels are anticipated to rise from the current ambient level of ca. 350 µl/liter to 500–600 µl/liter in the next 50 to 75 years. Plant scientists are artificially enhancing the CO2environment of crop plants to increase photosynthesis, which is currently limited by inadequate levels of CO2. It is not known how increases of CO2might affect consumers in the food chain. Population levels of sweetpotato whitefly (SPWF),Bemisia tabaci(Gennadius), were assessed with sticky traps placed in a field experiment wherein cotton was grown in open-top field chambers that were enriched with CO2at levels approaching 200% ambient concentration levels. Although trapping started at the first of June, only an occasional SPWF was caught until early August. At that time populations began to increase at an exponential rate similar to that observed in commercial cotton fields in Arizona and California in previous years. There was no difference in rate of buildup of SPWF in ambient and CO2-enriched chambers in either wet or dry irrigation treatment. Thus, it seems that raised CO2levels, either natural or artificial, do not affect SPWF populations.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.61

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Parasitic Hymenoptera caught on colored sticky panels placed in various forest microhabitats showed patterns of trap catch that could often be related to the hosts they attack. Parasites caught predominately on yellow panels, which mimic foliage, generally attack foliage-frequenting insects such as leaf-chewers or leaf-miners. The few parasites that did not respond predominately to yellow panels attack such hosts as psocids or eggs of stem- or pod-boring Lepidoptera. The observed correlations between patterns of trap catch and host preferences suggest that sticky panels may be useful in revealing host and microhabitat preferences of little-known parasites.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.64

出版商:Oxford University Press    

年代:1986

数据来源: OUP