共查询到20条相似文献,搜索用时 31 毫秒
1.
A quantitative risk assessment is needed for each quarantine pest insect to ensure quarantine security without sacrificing
the transparency of international trade. The probability of introduction, which is defined as the probability that one or
more reproductive individuals of a pest insect species pass the port, is one of the basic components determining the risk
of pest invasion. The probability depends on two biological characteristics of pests: mode of reproduction and spatial distribution
of insects per host plant. In this article, the probability of introduction was calculated for each of the following four
categories: (1) bisexual, gregarious pests; (2) bisexual, solitary pests; (3) parthenogenetic, gregarious pests; and (4) parthenogenetic,
solitary pests. Then, equations were derived to predict the effects of two prevention practices conducted before export: disinfestation
treatment and the subsequent export sampling inspection of consignments. These equations also enable estimation of the probability
of introduction under natural mortality, which thus can be used in place of the criterion of Maximum Pest Limit (MPL). The
method was applied to the Mexican fruit fly Anastrepha ludens (Loew), as an example. The contour graph of the probability of introduction indicated the optimal combination of the intensity
of two prevention practices that ensures a given security level. Existence of an antagonistic interaction was also indicated
between the disinfestation treatment and the subsequent sampling inspection.
Received: January 22, 1999 / Accepted: September 6, 1999 相似文献
2.
Katsumi Togashi 《Researches on Population Ecology》1991,33(2):245-256
Summary To understand the mechanism of spread of pine wilt disease caused by the pinewood nematode,Bursaphelenchus xylophilus, which is vectored by a cerambycid,Monochamus alternatus, the spatial distribution of trees weakened by the nematode was examined within aPinus thunbergii stand from June to October for 4 years. The weakened trees were distributed in a clumped pattern in 1980 and 1981, at an
early stage of infestation. In many cases, they showed a double-clumped pattern. The degree of aggregation was higher in June
or July than after August. They were uniformly distributed in June or July 1982 and in June 1983 whereas they showed a double-clumped
pattern after August. The trees were frequently weakened in June or July when they were near the trees weakened during the
previous year. At quadrat sizes of more than 25 m2, spatial overlapping was pronounced between trees weakened during June–July of the current year and those weakened in the
previous year. The seasonal changes in spatial distribution of weakened trees were explained by the interaction amongM. alternatus, B. xylophilus andPinus trees. 相似文献
3.
In a forest pest model, young trees are distinguished from old trees. The pest feeds on old trees. The pest grows on a fast scale, the young trees on an intermediate scale, and the old trees on a slow scale. A combination of a singular Hopf bifurcation and a “weak return” mechanism, characterized by a small change in one of the variables, determines the features of the mixed-mode oscillations. Period-doubling and saddle-node bifurcations lead to closed families (called isolas) of periodic solutions in a bifurcation corresponding to a singular Hopf bifurcation. 相似文献
4.
On an outbreak of the citrus flat-headed borer,Agrilus auriventrisE. Saunders in Nagasaki Prefecture
Ryoh-ichi Ohgushi 《Researches on Population Ecology》1967,9(1):62-74
Summary The process of an outbreak of the citrus flat-headed borer,Agrilus auriventris in Nagasaki Prefecture was described with some ecological considerations on causative factors.
This outbreak which showed a typical “Gradation”, initiated around 1958, and terminated in 1963. The peak year was seen in
1961. At first attack by the borer was restricted to old and weak trees, but it was also found in young and healthy trees
in the peak year.
Some environmental conditions in orchards were examined in relation to the intensity of infestation by the borer. Soil management
and drought seemed to have remarkable correlations with the borer's infestations.
Probably, this outbreak was caused by the weakening of citrus tree by gummosis and abnormal defoliation, aging of orchard
trees, and drought in the summer of 1959∼1960. Interrelation between these causes and processes are shown schematically in
Fig. 12. 相似文献
5.
Ei''ichi Shibata 《Researches on Population Ecology》1995,37(2):229-237
The inner bark of Japanese cedar,Cryptomeria japonica D. Don., is the main food of the sugi bark borer,Semanotus japonicus Lacordaire, but may also be involved in resistance to attack by the borer. I used newly hatched larvae to inoculate cedar
logs that had been cut 2-weeks to 12-months earlier, and undamaged living cedar trees. On living trees, all larvae were killed
by resin flow from the traumatic resin canals between the outer- and inner bark or between the inner bark and cambium. In
logs that were cut more than 4 months prior to inoculation, larvae were unable to complete development. In logs cut 2 weeks
prior to inoculation, almost all larvae were able to reach the adult stage but they were smaller in size than adults from
living trees damaged by this borer. These results suggest that poor nutrient conditions in the inner bark of logs affected
development and survival of the borer. Because of its nutritional advantage, living cedars provide a better environment for
the sugi bark borer. However, all larvae are killed by resin flow, suggesting that this insect is “in between” being primary
and secondary with respect to living trees, or a “weak” primary insect. The sugi bark borer seems to develop early in the
season so that early instar larvae encounter reduced amounts of resin flow and so that late-instar larvae feed mostly in summer
when nutrient levels in the inner bark are at their highest. 相似文献
6.
Summary An age-structured population dynamics model is presented that incorporates pheromone-trapping and food-trapping as control
methods for an insect pest. The model yields the following results. Low rates of pest survivorship allow lower trapping rates
for control. Species with long developmental periods are easier to control than those with shorter developmental periods (other
factors being equal) due to lower net survival. The rates of pheromone trapping alone for effective control are usually very
high. The combination of pheromone and food trapping allows control with much lower trapping rates than either method alone.
Even small amounts of immigration of adult pests into the control area renders pheromone control ineffective, whereas food
traps suppress both the immigrants and the resident population. Food- (or odor-) baited traps which attract both males and
females are only somewhat more efficient than those which attract females alone. The existence of density-dependent population
regulation assists the control program substantially, but this assistance declines as food trapping becomes a more important
part of the control program. Larval competition strongly affects the required trapping rates for eradication; species in which
all larvae exert strong competition are much easier to control than those in whic the younger larvae contribute little to
the total competitive depression. 相似文献
7.
Hugh J. Barclay 《Researches on Population Ecology》1992,34(1):131-141
Summary A methodology is developed to assess the effects of spatial distribution on the efficiency of insect pest control. This methodology
is especially applicable to pest control methods whose efficiency of action depends either positively or negatively on pest
density It is applied here to the sterile insect technique and pheromone trapping for male annihilation, which both depend
negatively on density. This methodology relies on quantifying clumps of various size and then relating this to efficiency
of control and predicting the total pest production given the information on clump sizes and efficiency of control for each
clump size. It is found that control is about four times as difficult for a population that is highly clumped (k of the negative binomial distribution=0.25) as for a regularly dispersed population. 相似文献
8.
Midori Tuda 《Researches on Population Ecology》1998,40(3):293-299
In an insect host (the cowpea weevilCallosobruchus maculatus)- parasitoidHeterospilus prosopidis) experimental system, the population densities of the component species oscillated for the first 20 generations and then
abruptly stabilized as the parasitoid density decreased. Examination of the host and parasitoid after the 40th generation
in the long-term experiment showed that (1) host larvae exhibited contest-type competition (killing other larvae inhabiting
the same bean), in contrast to the founder population being scramble-type competitors and (2) the parasitoid attack rate on
the host did not change. There was also an evolutionary trade-off between body size and the rates of larval survival and development,
suggesting a cost of contest competition on larval survivorship and development. I tested model predictions (Tuda and Iwasa
1998) that (1) host equilibrium population size should gradually decrease as the proportion of the contest type increases
and that (2) random attacks of the parasitoid on the host should reduce the rate of increase in proportion of the contest
type, and the effect should become manifest especially during the first 20 generations. Two of three host-only replicates
showed significant decrease in population sizes. Although the density of emerging adults per bean did not differ between replicates
of the host-only and host-parasitoid systems, comparison of the host body size between them on day 270 (at the 13th generation)
showed that the host was more contest-type in the host-only system than in the host-parasitoid system, as the model predicted,
and later on day 650 the effect of the parasitoid had disappeared. 相似文献
9.
Summary The life cycle of a non-diapausingT. urticae population was studied in a pear orchard in the southern part of Okayama Prefecture, western Honsh?, Japan. The mites overwintered
only on biennial weeds in the orchard without entering diapause, started to increase in number in early spring on them and
then moved to other weeds as they emerged. The occurrence of the mites on pear began in early May several weeks after the
unfolding of pear leaves and the population on pear was initiated by the migrants from the weeds around the base of pear trees.
The population on pear showed two distinct peak occurrences, one in June and the other in mid-autumn. After pear leaves dropped
in late autumn, the mites returned to biennial weeds for overwintering.
This work was supported in part by Grant-in-Aid No. 00556033 from the Ministry of Education, Science and Culture, Japan. 相似文献
10.
The outbreak mechanisms of the green rice leafhopper,Nephotettix cincticeps Uhler, in northern Japan
Intraspecific regulatory processes keep the population ofNephotettix cincticeps stable at a low density in southern Japan. In northern Japan, however, the yearly population density of the insect fluctuates
violently, and large outbreaks occasionally take place. To clarify the difference in the population dynamics between the two
regions, we analyzed light-trap and sweep-net sampling records from prefectural and national agricultural experimental stations.
The survival rate of the overwintering population decreased with increases in the period of continuous snow cover (PCSC) in
the north, and initial population densities in the years of long PCSC were too low for populations to reach equilibrium density
by the end of the active breeding season. This made yearly population fluctuations in the north much larger than in the south.
The equilibrium density in the north was higher than in the south. The higher equilibrium density presumably permits the higher
population density and larger yearly population fluctuations in the north. A major factor responsible for the difference in
equilibrium densities between the two regions is the difference in heading dates of the host plant (rice). Qualitative differences
among rice plant varieties, and among biotypes ofN. cincticeps, may also be important. 相似文献
11.
Hugh J. Barclay 《Researches on Population Ecology》1992,34(1):91-107
Summary An age-structured population model is used as a vehicle for presenting a method for the analysis of interactions between pairs
of insect pest control methods. This analysis is based on partitioning the total mortality acting on a population into its
constituent components from all known sources. Pairwise critical mortality curves are then constructed which represent the
combined mortality required for eradicating the pest population. Effort curves are then constructed from computing the mortality
resulting from a given amount of control effort. The convolution of the critical mortality curves and the effort curves then
yields the isoclines formed by the effort required of two control methods in combination to achieve eradication. This analysis
allows the prediction of either synergism or interference between the control methods and also helps explain patterns observed
in previous modelling of such combinations of pest control methods. 相似文献
12.
S. Akimoto 《Researches on Population Ecology》1995,37(1):81-89
Closely related species of gall-forming aphids are often associated with a single host species. SixTetraneura species coexist on the Japanese elm,Ulmus davidiana, in Sapporo, northern Japan. This paper describes the probabilities of coexistence on macro- and microgeographic scales (i.e.,
on host trees and host leaves) and examines whether coexistence with conspecific or heterospecific galls on leaves or shoots
has any effect on the fecundity of each aphid species using multiple regression. A Monte Carlo simulation showed that the
frequency distribution of the numbers of species on individual host trees differed significantly from that expected from the
null model. There were significantly positive or negative associations between species.Tetraneura radicicola andsorini always coexisted with other species on trees they infested. Multiple regression revealed that the coexistence of conspecific
or heterospecific galls on individual leaves had no influence on the fecundity ofradicicola andsorini, but had a negative influence on that of sp. O. On average,radicicola andsorini produced a smaller number of offspring in galls than sp. O, and obviously consumed only a small part of resources available
on the galled leaves. Evidence available suggests that although amensalism does arise between sp. O and other species, its
influence in not so strong as to exclude sp. O competitively from theTetraneura community. 相似文献
13.
Density dependence depends on scale; at larval resource patch and at whole population 总被引:1,自引:0,他引:1
Midori Tuda 《Researches on Population Ecology》1993,35(2):261-271
Summary A previous study (Tuda and Shimada, 1993) has shown that the equilibrium population size of the azuki bean beetle was lower
at 32°C than at 30°C and that this difference was due to a reduced maximum population size of emerged progeny through inside-bean
process. In this paper, these results were analyzed further on the scale of the individual bean where interaction among larvae
took place. Per-bean numbers of deposited eggs, hatched eggs, and emerged adults have been recorded at seven different parental
densities under the two temperature conditions.
Three individual-bean-scale process hypotheses that may explain the reduced maximum emergence density on the whole population
scale are suggested: (1) a lower maximum emergence per bean at 32°C than at 30°C, if the bean scale and the wholepopulation
scale share the same density-dependent pattern in adult emergence, (2) a limited range of hatched egg number per bean at 32°C,
resulting from the adult oviposition process outside beans, and (3) different patterns of density-dependent emergence between
the two different scales.
This study showed that the inside-bean pattern of responses on the bean scale was a simple saturated curve at 30°C, but one
with a discontinuous decline at higher hatched egg densities at 32°C. On the contrary, during outside-bean process, the peak
number of hatched eggs decreased on this scale as observed on the wholepopulation scale. I discuss why the extracted factor
of inside-bean process on the whole-population in the previous study could not be applied to the bean-scale pattern. 相似文献
14.
Combining pheromone-baited and food-baited traps for insect pest control: Effects of additional control by parasitoids 总被引:1,自引:0,他引:1
Hugh J. Barclay 《Researches on Population Ecology》1991,33(2):287-306
Summary Two age-structured population dynamic models are analyzed in which pheromone-baited trapping and food-baited trapping are
used simultaneously to eradicate an insect pest. The pest species is assumed to be under partial control by a host-specific
parasitoid species. The two models assume that density-dependent population regulation is accomplished either by host larval
competition or by means of oviposition interference among the parasitoids. The two trap types interact in a positive synergistic
manner and this combination appears to be very promising as a useful combination of pest control methods. Several features
of the system are examined; the feature which appears to cause the greatest problem is the possibility of the parasitoids
being attracted to the pheromone or the food traps. In either case, the degree of attraction does not have to be very great
to undermine the control effort. It is seen that food trapping becomes indispensible if host pheromone is used by the parasitoids
as a host-locating kairomone. If odor in the food traps is used by the parasitoids as kairomone, then the situation appears
more optimistic, as the reduction in efficiency of the food traps appears much less than with the pheromone traps when pheromone
acts as kairomone. 相似文献
15.
The relationship between the infestation rate of carambola fruits byBactrocera carambolae Drew and Hancock was investigated in a carambola orchard. Phenology of the fruits was found to influence percentage infestation
of fruits byB. carambolae. The proportion of unbagged or susceptible fruits infested varied with time of year and tended to decrease with the increase
of unbagged fruits available on the tree. The number of ovipunctures per fruit varied with fruit size and was also found to
be indicative of the number of adult insects (B. carambolae and parasitoids) that will emerge from each fruit. Higher number of susceptible fruits available on each tree also decreased
both the number of ovipunctures per fruit and the number of eggs laid per fruit, which could possibly be due to the strategy
of spreading the risk adopted by the femaleB. carambolae or a result of random selection with more hosts available. The main parasitoids recorded wereBiosteres vandenboschi (Fullaway) andB. arisanus (Sonan). The mean percentage of parasitism was 38.3% and it followed roughly that of infestation of fruits. 相似文献
16.
Summary Fertility schedules ofUnaspis yanonensis on citrus leaves were investigated from 1962 to 1971 for the first generation and from 1964 to 1971 for the second generation,
at the Okitsu Branch of the Fruit Tree Research Station in Shizuoka Prefecture. The fertility curves were commonly characterized
by a first major peak and a few subsequent minor peaks, although their shapes differed from year to year. Models estimating
these fertility curves of each generation were constructed in relation to the fluctuations in average daily temperature, on
the assumption that the curve was composed of two peaks, i.e., bimodal. Estimated curves were well fitted to observed ones.
Contribution B-173, Fruit Tree Res. Stn. 相似文献
17.
Summary Populations of the two-spotted spider mite,Tetranychus urticae Koch collected from various localities and from various host plants in Japan showed wide variations in diapause attribute.
Diapause percentages at 18°C/9L15D varied from nearly 100% in the north to 0% in the south-west. At intermediate latitudes
the mites showed wide inter-population variations. Populations on herbaceous hosts in vinyl- or glass-houses gave significantly
lower incidence of diapause than those on roses and deciduous fruit trees. Presence of winter hosts and better host quality
under protected environments seemed to favour non-diapausing mites.
The temperature threshold for diapause expression also varied widely among local populations. Northern populations consistently
had higher and less variable thresholds than populations at intermediate latitudes with thresholds between 15 and 18°C. Inbred
lines derived from a population in Kyoto exhibited a wide variation in diapause percentage at 18°C. These results show that
diapause inT. urticae is a quantitative threshold trait and that populations in central Japan consist of a variety of genotypes with different
diapause traits. This might provide a genetic source for adaptation to local and temporal variations in environmental conditions. 相似文献
18.
Izumi Washitani Yasushi Okayama Keiko Sato Hitomi Takahashi Takayuki Ohgushi 《Researches on Population Ecology》1996,38(2):249-256
Antagonistic biological interactions with flower consumers and pathogens may influence reproductive success of flowering plants,
affecting population dynamics and natural selection for floral traits. However, ecological and evolutionary consequences of
the interactions may depend on both spatial and temporal patterns of the interactions. In a forest metapopulation ofPrimula sieboldii E. Morren, an endangered clonal plant species, we measured between-subpopulation patterns of seed sets and interactions with
an influential flower consumer, a rove beetle,Eusphalerum bosatsu Watanabe, and a specific smut fungal pathogen,Urocystis tranzschelina (Lavrov) Zundel (Ustilaginales), for three years. Mean female fertility (seed set per flower) for individual subpopulations
fluctuated moderately among years but was highly variable within each year among the five subpopulations studied. In two subpopulations,
the impact ofEusphalerum beetle, was sufficiently large to result in almost complete failure in seed production over eight years including the three
study and five previous preliminary observation years. In the two other subpopulations, seed set failure was caused by infection
by the smut fungus. Infected capsules which constitute 10–30% of the capsules produced in the subpopulations were filled with
ustilospores instead of seeds. In the subpopulation that escaped flower damage byEusphalerum beetles and smut fungal infection, seed sets of both pin and thrum flowers were much higher than in the other subpopulations.
The spatial restriction of individual antagonistic agents to a part of subpopulations suggest that dispersal of the agents,
as well as the mode of spatial subdivision of the plant population would be important for determining the overall effects
of antagonistic interactions on plant performances at the metapopulation level. 相似文献
19.
Summary The effects of egg cannibalism, conditioned medium and the presence of quinone secretions on oviposition rate were studied
using single pairs of adults to eliminate any direct crowding effects. Most measurements were made on beetles confined to
the surface of the flour medium in plastic towers. Oviposition rate was decreased by about 58% when pairs were transferred
from fresh to conditioned medium; lowered about 25% when only quinones were present and the medium was still fresh; and enhanced
35% in dry conditions when beetles were provided with eggs to eat. Both the lowered oviposition rate in confined cultures
and egg-eating may be explained by natural selection at the individual level. Cannibalizing eggs boosts a female's oviposition
rate. The presence of quinones or conditioned medium indicates high population densities and acts as a signal for ceasing
oviposition and dispersing to avoid high egg mortality. In confined populations, this results in population regulation, while
in open populations, this strategy is a mechanism to avoid competition. It implies that the resource shortages normally experienced
by such organisms are relative, not absolute. 相似文献
20.
Preference and performance linkage in aPhyllocolpa sawfly on the willow,Salix miyabeana, on Hokkaido
A leaf-folding sawfly in the genusPhyllocolpa (Hymenoptera: Tenthredinidae) attackingSalix miyabeana (Salicaceae) was studied near Sapporo, Hokkaido, along the Ishikari River in 1993. Host plant individuals were young trees
4–7 years old which were growing rapidly, producing some long shoots with large leaves. On a gradient of shoot length classes
from 0–5 cm long to over 80 cm long, shoots were much more abundant in the shorter shoot length classes. However, attacks
by ovipositing females increased as shoot length increase from 0 attacks on the shortest shoots to 5.17 attacks per shoot
on the longest shoots. The frequency of attack per leaf increased from 0 to 0.13 over the same range of shoot lengths. This
pattern of attack resulted in a high frequency of larval establishment in feeding sites, between 0.96 and 1.00, in all attacked
shoot length categories. However, probability of survival to a late instar larva increased with shoot length and corresponded
to the attack pattern, indicating a preference-performance linkage between female ovipositional decisions and larval survival.
The patterns found for thisPhyllocolpa species are similar for galling sawflies in North America and Europe, especially in the genusEuura, members of which make stem, bud and leaf midrib galls. Extending the pattern to aPhyllocolpa species broadens identification of pattern and ultimately the generality of the emerging theory on populations of galling
sawflies. 相似文献