Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

scholarly journals Use of a Nitrate-Nonutilizing Mutant and Selective Media to Examine Population Dynamics of Fusarium oxysporum f. sp. spinaciae in Soil

2003 ◽  
Vol 93 (9) ◽  
pp. 1173-1181 ◽  
Author(s):  
Toshiaki Takehara ◽  
Katsuto Kuniyasu ◽  
Mitsutaka Mori ◽  
Hiroshi Hagiwara
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Fusarium Oxysporum ◽  
Selective Medium ◽  
Hot Water ◽  
Wild Type ◽  
Population Densities ◽  
Selective Media ◽  
Colony Forming Units ◽  
Soil Dilution

Determining the population density of the spinach wilt pathogen Fusarium oxysporum f. sp. spinaciae in soil with conventional Fusarium-selective media is quite difficult because nonpathogenic strains of F. oxysporum also grow on those media and are indistinguishable from the pathogen. Therefore, a nitrate-nonutilizing (nit) mutant of the pathogen and corresponding selective media were tested in an experimental approach to determine the population density of the pathogen. Colony forming units of the pathogen were countable after soil-dilution plating onto nit mutant-selective media MMCPA, CMP, and CGMBP. Colony forming units of wild-type Fusarium spp. were countable using a wildtype Fusarium-selective medium, GMBP. By combining nit mutant- and wild-type-selective media, the population densities of pathogenic and nonpathogenic F. oxysporum in the same soil could be measured selectively. This method was useful in studying population dynamics of the pathogen after different soil treatments. Soil disinfested with hot water or chloropicrin was amended with the nit mutant pathogen, and subsequent changes in population densities of the pathogen were compared with those in nontreated field soil. The pathogen rapidly proliferated in disinfested soil and wilt developed faster than in nontreated soil. When a nonpathogenic isolate of F. oxysporum was added at high density to sterilized soil prior to the pathogen, growth of the pathogen was greatly suppressed. Nonpathogenic F. oxysporum could not, however, reduce the density of preexisting pathogen.

Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

1977 ◽  
Vol 28 (4) ◽  
pp. 417 ◽  
Author(s):  
R Marchant ◽  
WD Williams
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Temperature Stress ◽  
Brine Shrimp ◽  
Dry Weight ◽  
Salt Lakes ◽  
Confidence Limits ◽  
Length Frequency ◽  
Population Densities ◽  
The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

scholarly journals Population Dynamics of the Sting Nematode in California Turfgrass

Plant Disease ◽  
2000 ◽  
Vol 84 (10) ◽  
pp. 1081-1084 ◽  
Author(s):  
Sadia Bekal ◽  
J. Ole Becker
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Golf Course ◽  
Golf Courses ◽  
Population Densities ◽  
Sampling Area ◽  
Coachella Valley ◽  
Belonolaimus Longicaudatus ◽  
Country Club ◽  
Desert Island

Population densities of Belonolaimus longicaudatus were monitored at monthly intervals at the Tamarisk country club golf course (1993 to 1994) and at the Annenburg Estates and Desert Island golf courses (1998). All three courses are located at Rancho Mirage, Coachella Valley, CA. The bermuda grass in the sampling area typically exhibited chlorosis at the beginning of April when the sting nematode populations began to increase. At the Tamarisk golf course, population density peaked in October, with 1,000 nematodes per 100 cm3 of soil, but declined rapidly, with the lowest population density occurring in December with approximately 50 nematodes per 100 cm3 of soil. At the Annenburg Estates and Desert Island golf courses, the nematode population densities peaked in June and July but declined rapidly to less than half of that density, presumably because of B. longicaudatus-caused host decline. Soil temperature and fluctuation of nematode densities were significantly correlated at all locations. Nematode distribution was greatest in the top 15 cm of soil except during the hottest summer months, when the population was higher at depths of 15 to 30 cm.

scholarly journals Fluctuations in population densities inform stability mechanisms in host-parasitoid interactions

2021 ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Functional Response ◽  
Discrete Time ◽  
Host Population ◽  
Reproduction Rate ◽  
Population Densities ◽  
Type Iii ◽  
Time Formalism ◽  
Large Fluctuations

AbstractPopulation dynamics of host-parasitoid interactions has been traditionally studied using a discrete-time formalism starting from the classical work of Nicholson and Bailey. It is well known that differences in parasitism risk among individual hosts can stabilize the otherwise unstable equilibrium of the Nicholson-Bailey model. Here, we consider a stochastic formulation of these discrete-time models, where the host reproduction is a random variable that varies from year to year and drives fluctuations in population densities. Interestingly, our analysis reveals that there exists an optimal level of heterogeneity in parasitism risk that minimizes the extent of fluctuations in the host population density. Intuitively, low variation in parasitism risk drives large fluctuations in the host population density as the system is on the edge of stability. In contrast, high variation in parasitism risk makes the host equilibrium sensitive to the host reproduction rate, also leading to large fluctuations in the population density. Further results show that the correlation between the adult host and parasitoid densities is high for the same year, and gradually decays to zero as one considers cross-species correlations across different years. We next consider an alternative mechanism of stabilizing host-parasitoid population dynamics based on a Type III functional response, where the parasitoid attack rate accelerates with increasing host density. Intriguingly, this nonlinear functional response makes qualitatively different correlation signatures than those seen with heterogeneity in parasitism risk. In particular, a Type III functional response leads to uncorrelated adult and parasitoid densities in the same year, but high cross-species correlation across successive years. In summary, these results argue that the cross-correlation function between population densities contains signatures for uncovering mechanisms that stabilize consumer-resource population dynamics.

scholarly journals Depth Distribution of Rotylenchulus reniformis Under Different Tillage and Crop Sequence Systems

2003 ◽  
Vol 93 (9) ◽  
pp. 1182-1189 ◽  
Author(s):  
A. Westphal ◽  
J. R. Smart
Keyword(s):  
Population Density ◽  
Conventional Tillage ◽  
Grain Sorghum ◽  
Reduced Tillage ◽  
No Tillage ◽  
Rotylenchulus Reniformis ◽  
Population Densities ◽  
Tillage Systems ◽  
Crop Sequence ◽  
Ridge Tillage

The population density of the reniform nematode, Rotylenchulus reniformis, was monitored at depths of 0 to 30, 30 to 60, 60 to 90, and 90 to 120 cm in a tillage and crop sequence trial in south Texas in 2000 and 2001. Main plots were subjected to three different tillage systems: conventional tillage (moldboard plowing and disking), ridge tillage, and no-tillage. Subplots were planted with three different crop sequences: spring cotton and fall corn every year; spring cotton and fall corn in one year, followed by corn for two years; and cotton followed by corn and then grain sorghum, one spring crop per year. The population density of R. reniformis on corn and grain sorghum was low throughout the soil profile. In plots planted with spring cotton and fall corn every year, fewer nematodes were found at depths of 60 to 120 cm in the no-tillage and ridge tillage systems than in the conventional tillage system. Population densities were lower at depths of 0 to 60 cm than at 60 to 120 cm. Soil moisture and cotton root length did not affect nematode population densities in the field. When soil was placed in pots and planted with cotton in the greenhouse, lower population densities developed in soil taken from depths of 0 to 60 cm than in soil from depths of 60 to 120 cm. Final nematode populations were similar in size in soil from the different tillage systems, but reproductive factors were higher in soil from plots with reduced-tillage systems than in soil from plots with conventional tillage. Reduced-tillage practices lowered the risk of increases in R. reniformis populations and reduced population densities following 2 years of non-hosts throughout soil depths, but population densities resurged to the same high levels as in soil planted with cotton every year during one season of cotton.

scholarly journals Stochasticity in host-parasitoid models informs mechanisms regulating population dynamics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Functional Response ◽  
Discrete Time ◽  
Host Population ◽  
Reproduction Rate ◽  
Population Densities ◽  
Type Iii ◽  
Time Formalism ◽  
Large Fluctuations

AbstractPopulation dynamics of host-parasitoid interactions have been traditionally studied using a discrete-time formalism starting from the classical work of Nicholson and Bailey. It is well known that differences in parasitism risk among individual hosts can stabilize the otherwise unstable equilibrium of the Nicholson-Bailey model. Here, we consider a stochastic formulation of these discrete-time models, where the host reproduction is a random variable that varies from year to year and drives fluctuations in population densities. Interestingly, our analysis reveals that there exists an optimal level of heterogeneity in parasitism risk that minimizes the extent of fluctuations in the host population density. Intuitively, low variation in parasitism risk drives large fluctuations in the host population density as the system is on the edge of stability. In contrast, high variation in parasitism risk makes the host equilibrium sensitive to the host reproduction rate, also leading to large fluctuations in the population density. Further results show that the correlation between the adult host and parasitoid densities is high for the same year, and gradually decays to zero as one considers cross-species correlations across different years. We next consider an alternative mechanism of stabilizing host-parasitoid population dynamics based on a Type III functional response, where the parasitoid attack rate accelerates with increasing host density. Intriguingly, this nonlinear functional response makes qualitatively different correlation signatures than those seen with heterogeneity in parasitism risk. In particular, a Type III functional response leads to uncorrelated adult and parasitoid densities in the same year, but high cross-species correlation across successive years. In summary, these results argue that the cross-correlation function between population densities contains signatures for uncovering mechanisms that stabilize consumer-resource population dynamics.

Mucuna deeringiana (Bort) Merr. vs. the corm weevil, Cosmopolites sordidus Germar (Coleoptera: Curculionidae), in plantains

1969 ◽  
Vol 89 (3-4) ◽  
pp. 201-210
Author(s):  
Amparo Salazar ◽  
Alberto Pantoja ◽  
Juan Ortiz
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Management Practices ◽  
Production Costs ◽  
Cosmopolites Sordidus ◽  
Adult Density ◽  
High Population Density ◽  
Population Densities ◽  
Insect Density ◽  
The Relationship

The effect of the legume Mucuna deeringiana on Cosmopolites sordidus population dynamics and damage was studied in two planting systems: intercropping with mucuna and mucuna as green mulch before establishing the plantain. The relationship between C. sordidus adult density and larval damage was also studied. The presence of M. deeringiana affected the incidence of C. sordidus.The data suggest that C. sordidus adults are attracted by M. deeringiana, but additional studies are needed to better understand the relationship between the legume and the insect. The presence of M. deeringiana did not affect plantain height, stem diameter, or sucker production if the legume was eliminated four months after planting. However, management practices to establish and cultivate the legume increased production costs. Although C. sordidus population densities were low during most of the year, a high population density was recorded from November to January. A second population explosion was recorded between June and August. The highest insect density recorded was 3.5 insects per trap.

The effect of varying plant population density on the seed yield of Navy beans (Phaseolus vulgaris)in south-east Enland

1977 ◽  
Vol 88 (3) ◽  
pp. 567-576 ◽  
Author(s):  
D. H. Scarisbrick ◽  
J. M. Wilkes ◽  
R. Kempson
Keyword(s):  
Phaseolus Vulgaris ◽  
Population Density ◽  
Seed Yield ◽  
Plant Density ◽  
Growing Season ◽  
Plant Population ◽  
Population Densities ◽  
Growing Seasons ◽  
Navy Beans ◽  
Plant Population Density

SUMMARYNavy beans were precision drilled in 1973–5 at a range of plant population densities. Within each growing season the density treatments did not influence seed yield, but mean yields differed significantly between years. The results suggest that cultivars similar to Purley King can only be regarded as a reliable break crop in a season such as 1973 which was slightly warmer and drier in mid-summer than average. Although the rate of drying increased with increasing plant density in two of the growing seasons, no practical advantages are proposed.

scholarly journals Population density of Tibraca limbativentris on flood irrigated rice and alternative host plants

2018 ◽  
Vol 53 (3) ◽  
pp. 265-278 ◽  
Author(s):  
Mauricio Paulo Batistella Pasini ◽  
Alessandro Dal’Col Lúcio ◽  
Alberto Cargnelutti Filho ◽  
Ana Lúcia de Paula Ribeiro ◽  
João Fernando Zamberlan ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Host Plant ◽  
Host Plants ◽  
Insect Population ◽  
Alternative Host ◽  
Population Densities ◽  
Temporal Dependence ◽  
Phenological Stages ◽  
Irrigated Rice

Abstract: The objective of this work were to evaluate the population dynamics of the rice stem bug (Tibraca limbativentris) around and in flood irrigated rice cultivation area, to quantify the insect population flow between crops and host plants, and to determine the effect of the species, the diameter of the plant, and the distance of the host plant from the border on the rice stem bug population. The work was conducted in the 2012/2013 harvest and in the off-season, with sampling of rice, Andropogom bicornis, and Andropogon lateralis plants in six cultivated areas, in order to count the number of insects. The population density of the rice stem bug in irrigated rice and alternative host plants presents spatial and temporal dependence. In the cultivated areas, the population density of the rice stem bug increases according to the evolution of the rice phenological stages, with the highest densities concentrated in regions close to the crop borders. The diameter and species of the host plant affect the rice stem bug population. Andropogon bicornis plants have higher population densities than A. lateralis, and plants with larger diameters show higher population densities of the rice stem bug. In the off-season, the greatest population of the rice stem bug on host plants is concentrated up to 45 m from the crop border, but it can disperse until 150 m.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

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