Weed Habitat Research Articles

Devising newer cropping strategy for eradicating weed niches – A review

The world's population will continue to expand in the future, necessitating increased food production to meet people's nutritional needs. Weed infestation is a key stumbling block in increasing global food productivity. In conventional agriculture, herbicides are the primary weed-control tool. Herbicide use has, however, led in the emergence of herbicide-resistant weeds, making weed control difficult. Weed management practises that are both sustainable and environmentally benign favour crop plants by reducing weed-crop competition. Concerted efforts have been taken with the objective to formulate suitable cropping strategies for reducing weed niches. Hence, the current literature evaluation focuses on the extent to which cropping strategies aids to reduce weed habitat.

Management of Invasive Water Hyacinth as Both a Nuisance Weed and Invertebrate Habitat

Author(s): Donley Marineau, Erin; Perryman, Matthew J.; Lawler, Sharon P.; Hartman, Rosemary K.; Pratt, Paul D. | Abstract: Invasive species have many detrimental ecological and socio-economic effects. However, invasive species can also provide novel habitat for native species. The growing rate of biological invasions world-wide presents an urgent dilemma: how can natural resource managers minimize negative effects of invasive species without depleting native taxa that have come to rely on them? Adaptive management can provide a means to address this dilemma when invasive species management plans are crafted in novel environments. We present a case study of research in support of adaptive management that considers the role of invasive water hyacinth (Eichhornia crassipes [Mart.] Solms [Pontederiaceae]) management, using herbicides, in aquatic food web functioning in the Sacramento–San Joaquin River Delta of California, USA (the “Delta”). We hypothesized that herbicide applications under current management protocols would reduce the abundance and diversity of aquatic invertebrates because they would alter both structural and biological habitat. Using a Before, After, Control, Intervention (BACI) experiment, we sampled invertebrates per gram plant biomass before and 4 weeks after glyphosate applications in treated and untreated locations. There was more plant biomass in the late-season samples because dead, dying, and living plant materials were compacted. However, there were no detectable differences between control and treated sites — or for samples before versus after the treatment date—for invertebrate abundance, species richness, or evenness. This case study demonstrates that even decaying water hyacinth serves as habitat for invertebrates that may be forage for Delta fishes. We concluded that current management practices using glyphosate do not affect invertebrate abundance during a month-long period of weed decay. These results provide valuable feedback for the “evaluate and respond” component of the adaptive management process for water hyacinth control, and demonstrate how managers globally can and should consider potential food web effects in the course of their invasive species management efforts.

Shape, colour plasticity, and habitat use indicate morph-specific camouflage strategies in a marine shrimp

BackgroundColour and shape polymorphisms are important features of many species and may allow individuals to exploit a wider array of habitats, including through behavioural differences among morphs. In addition, differences among individuals in behaviour and morphology may reflect different strategies, for example utilising different approaches to camouflage. Hippolyte obliquimanus is a small shrimp species inhabiting different shallow-water vegetated habitats. Populations comprise two main morphs: homogeneous shrimp of variable colour (H) and transparent individuals with coloured stripes (ST). These morphs follow different distribution patterns between their main algal habitats; the brown weed Sargassum furcatum and the pink-red weed Galaxaura marginata. In this study, we first investigated morph-specific colour change and habitat selection, as mechanisms underlying camouflage and spatial distribution patterns in nature. Then, we examined habitat fidelity, mobility, and morphological traits, further indicating patterns of habitat use.ResultsH shrimp are capable of changing colour in just a few days towards their algal background, achieving better concealment in the more marginal, and less preferred, red weed habitat. Furthermore, laboratory trials showed that habitat fidelity is higher for H shrimp, whereas swimming activity is higher for the ST morph, aligned to morphological evidence indicating these two morphs comprise a more benthic (H) and a more pelagic (ST) life-style, respectively.ConclusionsResults suggest that H shrimp utilise a camouflage strategy specialised to a limited number of backgrounds at any one time, whereas ST individuals comprise a phenotype with more generalist camouflage (transparency) linked to a more generalist background utilisation. The coexistence within a population of distinct morphotypes with apparently alternative strategies of habitat use and camouflage may reflect differential responses to substantial seasonal changes in macroalgal cover. Our findings also demonstrate how colour change, behaviour, morphology, and background use all interact in achieving camouflage.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0796-8) contains supplementary material, which is available to authorized users.

Weed seeds, not grain, contribute to the diet of wintering skylarks in arable farmlands of Western France

Assessing the diet of farmland birds during the wintering period has important implications for conservation. However, for some species such as the skylark, the diet composition remains poorly known across its wintering range. On the basis of gizzards collected in mid-winter over a 10-year interval and in two regions of Western France, we quantified the contribution of seeds and investigated whether the diet differed between sexes, regions and period and whether seeds entered the diet with respect to their size, nutritive value or their spring occurrence within the farmland landscape. Also, the amount of seeds that birds need to consume for meeting their daily energy requirements was assessed by simulation and compared with estimates measured in captive individuals. Thirty-eight seed species belonging to 16 families were identified in gizzards. All species but one were weeds, and cereal grains were absent from all gizzards. The diet differed slightly between sexes but contrasted between regions and periods. We found no clear evidence for a selective intake based on seed traits. Conversely, our results suggest that weed seeds would enter the diet with respect to their relative occurrence. Our simulation indicated that birds should ingest about 8 g (4200-5600 seeds) to meet their daily requirements. A mean value of 6.7 g per day was measured in captive skylarks. These results suggest that the maintenance of rich weed habitats is a crucial issue for populations of skylarks that overwinter in agricultural landscapes of Western France.

Weed dispersal by farming at various spatial scales. A review

Reducing pesticide use in agriculture is necessary to preserve natural resources. However, pest control without pesticides is a challenging issue. In particular, weed infestation may cause severe losses of crop yield. Weeds have been traditionally managed solely at the field level. However, larger scales must be considered because invasive and herbicide-tolerant weeds are spreading over larger scales. This review discusses three spatial scales at which agricultural management might affect the dispersal of weeds and, in turn, their distribution and abundance in agricultural fields. The main points are: (1) at the field level, crop and margin management impact mass effect, i.e., local exchanges between the field margin and the cultivated field; (2) at the farm level crop allocation, the management of field boundaries and agricultural circulation in the farm strongly impact the intensity and direction of weed dispersal; and (3) at the landscape level, the spatial farms distribution controls the distribution of weed habitat and, in turn, landscape species pool and long-distance weed dispersal. We conclude that weed dispersal is driven by agricultural management at multiple scales. Weed scientists should thus extend their view on weed dispersal from within-field scales to among-field and landscape scales.

Biocontrol Ability of Puccinia abrupta var. partheniicola on Different Growth Stages of Parthenium Weed (Parthenium hysterophorus L.)

A research was conducted to investigate the biological control ability of Puccinia abrupta var. partheniicola infected to parthenium weed (Parthenium hysterophorus L.) at different stages of growth in a glasshouse. The study also investigated the combined effect of the infection and the competitor plant, i.e. buffel grass (Cenchrus ciliaris L.), a pasture species usually found in the weed habitat in Central Queensland. The 2 × 3 factorial experiment was arranged in a completely randomized design with six replicates in each treatment. The parthenium weeds were planted with or without buffel grass. The plants were inoculated with P. abrupta var. partheniicola urediniospores either at the rosette, flowering or mature growth stage of development. As controls, an additional six non inoculated plants with and without buffel grass were planted. The results showed that P. abrupta var. partheniicola affected more on the younger plants than on the older ones. Its infection decreased the plant height. A higher reduction in plant above ground biomass was recorded because of the rust when the plants were inoculated at the rosette growth stage of development in the presence of competition. The impact of the rust was greatest on the ability of parthenium to produce seeds.

Effect of Tillage on Cotton Aphids (Homoptera: Aphididae), Pathogenic Fungi, and Predators in South Central Georgia Cotton Fields

Two species of fungi, Neozygites fresenii Nowakowski (Batko) and Pandora neoaphidis Remaudiere and Hennebert (Humber), pathogens of the cotton aphid, Aphis gossypii Glover, were studied in 12 south central Georgia cotton fields under conservation or conventional tillage in 2003 and 2004. Aphids and ants on cotton plants were enumerated in both years, and aphid predators (coccinellids, lacewings, and spiders) were counted in 2004. Plant sampling began the first week of June and continued for 16 wks in 2003 and for 14 wks in 2004. Numbers of aphids on cotton plants increased until the first week of July and declined thereafter. More aphids were present on plants in 2004 than in 2003 for the first 9 wks of sampling, but did not differ thereafter. More aphids were present on plants under conservation tillage than under conventional tillage only between weeks 3–8. Pandora neoaphidis was detected in aphids in midMarch by monitoring with pan traps on field margins. Neozygites fresenii, in contrast, was not observed until 18 June 2003 and 16 June 2004, and peaked simultaneously with the aphid population and then declined. The incidence of P. neoaphidis was less than that of N. fresenii, but peaked simultaneously with it in the first week of July. Ants, primarily the red imported fire ant, Solenopsis invicta Buren, occurred in larger numbers in fields under conservation tillage than under conventional tillage, apparently because of greater disruption of soil and weed habitat under conventional tillage. In both tillage types, coccinellids peaked early in the season and lacewings late in the season, with larger numbers of coccinellids present in fields under conservation tillage. Although there was a sharp peak in lacewing numbers late in the season under conservation tillage, overall lacewing numbers were not different under the 2 types of management. Spider numbers increased gradually throughout the growing season, with only slightly higher numbers present under conservation tillage. The effects of different tillage methods were more evident on the aphids and their predators than on the fungal pathogens.

Population Dynamics of Cucumber mosaic virus in Melon Crops and in Weeds in Central Spain

ABSTRACT Understanding epidemiology and evolution of plant viruses requires knowledge of their ecology: obtaining information about the dynamics and genetic structure of viral populations in their various hosts is necessary to analyze host specialization and to identify reservoirs and inoculum sources. We present here a 3-year analysis of the population dynamics of Cucumber mosaic virus (CMV) in Central Spain in weed hosts and melon. CMV infection in weed hosts was detected throughout the year and showed a clear seasonality, with maximum incidence of 20 to 30% in summer and autumn. The dynamics of CMV incidence were different in various weed habitats (i.e., fallow fields, edges, and wastelands), which differed in stability due to the degree of human intervention. CMV incidence in weed habitats was correlated with the amount of vegetation, estimated both as biomass and as soil cover by plants. CMV population dynamics in melon crops was unrelated to that in weed habitats. Genetic characterization by ribonuclease protection assays and biological characterization on differential hosts showed no significant differences in the frequency of genotypes or biotypes for CMV isolates from weeds or melon. Hence, different population dynamics in various hosts and habitats has not resulted in population differentiation, suggesting that migration between hosts and habitats prevents fragmentation of the population.

Structure and characteristics of parasitoid communities in a rice field and adjacent weed habitat

Structure and characteristics of parasitoid communities in a rice field and adjacent weed habitat

Comparison of the Seasonal Occurrence of the Major True Spiders (Araneida) in some Crop Systems and A Natural Habitat in Western Saudi Arabia

The seasonal occurrence of spider community belonging to 10 families was determined in three different habitats: vegetable, date-palm and mixed weed habitats in Western Saudi Arabia. Different densities were observed in all habitats, however the vegetable habitat showed high number of spiders. This may be due to variability of food sources. The wolf spider family (Lycosidae) was predominant in all habitats. Moreover the analysis of variance showed that 3 families Lycosidae, Zodariidae and Pholcidae had significant differences when their densities were compared between the three habitats. The number of generations vary between 2 and 3 throughout the seasons.

Weeds in field margins: a spatially explicit simulation analysis of Canada thistle population dynamics

Abstract Field margin weeds may contribute to the invasion and persistence of weeds in arable fields. Experimental studies of this hypothesis, however, have been inconclusive. We examined the role of field margin weed populations with a spatially explicit simulation model of Canada thistle population dynamics. We measured the contribution of field margin populations to weed pressure in the field across a wide range of parameter values and compared the weed control value of efforts applied to the field margin to that of similar efforts applied to the field. Under most combinations of parameter values, field margin weeds contributed little to weed pressure in the field, suggesting that controlling field margin weeds may often be of little value. Two conditions appeared to be necessary for field margin weeds to influence weed population dynamics within the field: the presence of unoccupied weed habitat, which increased the importance of dispersal to population growth, and high dispersal rates of field margin...

Fishes of the Tropical Eastern Pacific

A comprehensive, color-illustrated guide to the marine fishes of the region extending from the central Gulf of California, southward to Ecuador. It covers 680 species, primarily species that inhabit inshore reefs and adjacent sand, rubble, and weed habitats. Pelagic fishes, including tunas, mackeral

Population Density of Empoasca fabae (Homoptera: Cicadellidae) in Weedy Beans

The response of Empoasca fabae (Harris) to beans, Phaseolus vulgaris L., in four weed habitats, bean monocultures, beans with Brassica kaber (D.-C.), beans with weeds that were removed in early July, and unweeded beans, was examined by visual and D-Vac samples. Weeds in the unweeded treatment were mixed broadleaf and grassy weeds. Visual samples showed that leafhopper density per bean leaflet was highest in bean monocultures, lowest in unweeded beans, and intermediate in the remaining weed habitats. D-Vac samples showed no difference in leafhopper density per area among weed habitats. D-Vac samples included leafhoppers living on the associated weeds, whereas visual samples restricted population estimates to leafhoppers on bean plants. These results suggest that mixed broad leaf and grassy weeds did not affect total E. fabae population density per land area, but did affect the spatial distribution of E. fabae among weedy and cultivated host plants.

The relationship between seed dormancy, seed size and weediness, in Crepis tectorum (Asteraceae)

I examined the germination characteristics of weed and outcrop populations of Crepis tectorum to test the hypothesis that the presumably more ephemeral weed habitat favors the highest levels of seed dormancy. The winter annual habit characterizing most plants of this species was reflected in a rapid germination of seeds sown in late summer. A slightly higher fraction of surface-sown seeds of weed plants delayed germination. Buried seeds of weed plants also survived better than seeds produced by plants in most outcrop populations, supporting the idea that weediness favors seed dormancy and a persistent seed bank. However, the differences in seed dormancy between the two ecotypes were small and not entirely consistent. Furthermore, high levels of seed dormancy were induced during burial in the outcrop group, suggesting that there is a potential for a dormant seed population in this habitat as well. Demographic data from one of the outcrop populations verified the presence of a large between-year seed bank. Possible environmental factors favoring seed dormancy in outcrop populations are discussed. The unusually large seeds of weedy Crepis contrasts with the relatively small difference in seed dormancy between the two ecotypes.

Foraging territoriality of the imported fire ant,Solenopsis invicta Buren, in surgarcane as determined by neutron activation analysis

Imported fire ant,Solenopsis invicta Buren, colonies in weedy and weed-free Louisiana sugarcane habitats were labeled with the nonradioactive, stable-activable tracer element samarium, to be compatible with an agroecosystem in current food production. Instrumental neutron activiton analyses of samarium revealed that the ants foraged 9% of the sampling stations in weed-free areas and 6.4% of the stations in weed habitats. The significantly smaller territorial size in weedy areas was a result of more dense prey populations, which, encouraged greater ant colonization and 25% more foraging activity per unit area.S. invicta foraging activity was negatively correlated (r=−0.68; P≤0.02) with that of another ant,Paratrechina vividula.

Phenotypic plasticity inCrepis tectorum (Asteraceae)

Two experiments were carried out using two different approaches to compare populations ofCrepis tectorum (Asteraceae). One was based on a comparison of means of various vegetative and reproductive characters and another was based on a comparison of response patterns of the same characters in a series of environments. Population divergence within two earlier recognized form series, one from weed habitats and one from alvar habitats on Baltic islands, resulted in a partially overlapping pattern in cluster analyses based on character means. However, the pattern revealed by a comparison of the direction and amount of plastic response suggested that populations within the two form series had more similar response patterns than other combinations of populations. It was concluded that patterns of plasticity may provide useful additional information on the overall similarity among taxa. An hypothesis that plants in weed populations should exhibit a greater phenotypic response to the environments than plants in alvar populations was rejected.

Influence of Selected Weed Control Practices on Araneid Faunal Composition and Abundance in Sugarcane

In a 3-year study of spiders collected in weedy versus weed-free habitats in Louisiana sugarcane fields, pitfall trap catches showed no differences in diversity (as determined by the number of species and their individuals) of ground associated spider fauna. Diversity of foliage associated spider fauna was 27% higher in grass and mixed weedy than in weed-free and broadleaf habitats in 1983, based on D-Vac samples. Sweep net counts in 1984 revealed a 39% higher foliar spider diversity in weedy than in weed-free habitats. Overall spider abundance in sugarcane decreased with seasonal progression. Additionally, comparisons of weed-free, grass, broadleaf, and mixed weed habitats showed that weed floral composition seems to have little effect on the collective spider abundance and faunal diversity.

Weeds, Polyploids, Parthenogenesis, and the Geographical and Ecological Distribution of All-Female Species of Cnemidophorus

have one primary center of distribution, which is in the North American Southwest adjacent to the Continental Divide and the area of confluence between the Rocky Mountains and the Mexican Plateau. Cnemidophorus cozumelus presents the single contrast to the distributional pattern of the remaining eight species, being distributed along the margin of the Yucatan Peninsula. The habitats occupied by the various all-female species are diverse but have a common denominator. Each habitat is characterized by such descriptive terms as disclimax, marginal, ecotone, transient, extreme, and perpetually disturbed, all of which define a weed habitat. The presence of such habitats at the time of origin of parthenogenetic individuals from hybridization between bisexual species looms as a critical factor for the

Habits of Microtus californicus Revealed by Automatic Photographic Recorders

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