In this paper, we describe the system design and capabilities of the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope at the conclusion of its construction project and commencement of science operations. ASKAP is one of the first radio telescopes to deploy phased array feed (PAF) technology on a large scale, giving it an instantaneous field of view that covers $31\,\textrm{deg}^{2}$ at $800\,\textrm{MHz}$. As a two-dimensional array of 36$\times$12 m antennas, with baselines ranging from 22 m to 6 km, ASKAP also has excellent snapshot imaging capability and 10 arcsec resolution. This, combined with 288 MHz of instantaneous bandwidth and a unique third axis of rotation on each antenna, gives ASKAP the capability to create high dynamic range images of large sky areas very quickly. It is an excellent telescope for surveys between 700 and $1800\,\textrm{MHz}$ and is expected to facilitate great advances in our understanding of galaxy formation, cosmology, and radio transients while opening new parameter space for discovery of the unknown.

The dispersion of ethylene in the soil after application from a backpack ethylene applicator (BPEA) was determined using a bioassay of witchweed [Striga asiatica (L.) Kuntze # STRLU] seed germination. Witchweed seed were buried in packets in ridged seedbeds under field conditions. Ethylene dispersion was better when injected into the furrow than into the ridge top. Injections 30 cm deep were more effective in causing seed germination than injections 15 cm deep. Seed germination induced by ethylene injection into the furrow 30 cm deep was 13% more than that obtained from the ridge top injection 15 cm deep. Seed germination as high as 90% was obtained at soil depths to 75 cm at a horizontal distance of 100 cm from the point of ethylene injection. Ethylene diffused up to 300 cm horizontally and to 75 cm vertically to cause at least 45% seed germination in a field of Lakeland soil (Typic Quartzisamment). The BPEA was found to be an effective application tool in witchweed control operations.

Water use by weeds is one type of loss that contributes to the cost of weeds to agriculture. Water use efficiency provides a mechanism by which water use by weeds can be estimated. Uncontrolled weed growth could result in estimated irrigation costs exceeding $50.00/ha. Weeds like barnyardgrass at threshold densities in irrigated crops like sugarbeet or tomato are estimated to increase production costs by about $20.00/ha depending on water cost.

WSSA members were surveyed in 1993–1994 to determine their perceptions of the contribution of weed biology to weed management. A questionnaire was included in the society newsletter, from which 152 responses were returned by mail or collected at the 1994 annual meeting. Over half the respondents felt that the overall contribution of weed biology to weed management had been moderate to high. Aspects of population dynamics and competition emerged as the areas that respondents felt should have the greatest impact on weed management in the future. The areas of computer modeling, interactions between weeds and other pests, and seedbank dynamics were predicted to show the greatest increases in importance in the future. The relative importance of taxonomy and weed identification was expected to decrease. Allelopathy, morphology and anatomy, and genetics and evolution were considered least likely to be important to weed management.

Witchweed (Striga asiatica Lour. ♯4 STRLU) seed remained viable for 6 yr under open-shelf laboratory conditions and for 14 yr when deep buried under field conditions. Seed kept in normal atmosphere of the laboratory for < 1 through 6 yr had the following germination percentages: 2, 95, 95, 94, 83, 38, and 7. Newly harvested seed will not germinate because of postmaturity ripening requirements. There were no viable seed after 7 yr of shelf storage in the laboratory. Seed buried in the field gave 60 to 90% germination the first season after production. Annual recovery and testing showed a gradual reduction in viability to 10% at year 14 for the deepest buried seed; shallower buried seed expired sooner. No germination occurred thereafter.

Corn (Zea mays L. ‘DeKalb 640′), kidney beans (Phaseolus vulgaris L. ‘Light red’) and oats (Avena sativa L. ‘Kanota’) were grown in solution culture and the roots exposed to radioactively labeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. The radioactivity from 3H-atrazine, or its metabolites, was located in microautoradiographs of corn leaf sections, almost exclusively at the perimeter of the vascular bundles, and was primarily confined to the cell walls and intercellular spaces, with no activity associated with subcellular organelles. Radioactivity from 3H-atrazine in oat leaf section microautoradiographs was primarily associated with the chloroplasts, with no evidence of radioactivity specifically associated with other subcellular organelles. Sucrose density gradient centrifugation of homogenized leaf tissue following exposure of the plants to 14C-atrazine showed that most of the radioactivity was associated with the light cell fragments and cytoplasm for the test species. There was no accumulation of 14C-activity in any of the heavier subcellular organelles from corn leaf cells. A peak of radioactivity was associated with the chloroplast fraction from oat and kidney bean leaves.

Seedling alfalfa exhibited increased phytotoxicity from bromoxynil when applications were made with temperatures greater than 28 C both in controlled environments and in the field. Treatments applied in the morning were more phytotoxic than treatments made in the late afternoon. In laboratory experiments, inhibition of oxygen evolution occurred within 1 h after treatment. The amount of permanent damage sustained was dependent on the rate of bromoxynil and the length of time the alfalfa was exposed to light or darkness immediately after spraying. Bromoxynil treatments in cool weather and/or in the late afternoon should minimize injury to the crop.

Individual barnyardgrass plants were grown in the absence of competition in a common garden environment. Cohorts were initiated in mid-March, late April, early June, mid-July, mid-August, and mid-September. Plants within a cohort varied from prostrate to upright. Early and late cohorts required slightly longer to achieve flowering and seed shatter than those initiated in late spring and early summer. The onset and development of senescence varied by as much as 5 wk between individuals within a cohort, and senescence progressed more rapidly for plants in later cohorts. Longest tiller length per plant averaged 150 cm and did not differ by cohort, but within cohort variation was approximately 33%. The number of tillers per plant declined with increasing delay in cohort initiation; within cohort variation exceeded 40%. Leaf numbers decreased from more than 10,000 per plant to less than 400 per plant with increasing delay in cohort initiation date. Individuals within a cohort had more than two-fold variation in leaf numbers. The number of inflorescences decreased from more than 4500 per plant to less than 100 with increasing delay in cohort initiation. Mean inflorescence length and frequency of different inflorescence lengths per plant varied between plants within a cohort. Vegetative biomass exceeded 3000 g for many plants in the early cohorts, and decreased to less than 25 g per plant for some individuals in the September cohort. More than two-fold variation in biomass occurred between plants within a cohort. Plasticity in morphology and phenology may contribute to the success of barnyardgrass as a weed.

Barnyardgrass at 10 or more plants per 1 m of row caused over 80% root yield loss in spring-sown sugarbeets in California. The yield loss decreased to between 5 and 20% when barnyardgrass densities were one plant ever 2 to 3 m of crop row. The relationship between crop yield and barnyardgrass density was described by a rectangular hyperbolic function. The economic threshold density was in the range of one barnyardgrass plant every 5 to 20 m or row. Barnyardgrass plants growing at densities of less than one plant per 1 m in sugarbeets experienced only interspecific competition. Such individual barnyardgrass plants were estimated to produce from 30 000 to over 200 000 seeds, with an average of 100 000 seeds per plant. This seed production equated to a seed rain of about 4000 to nearly 20 000 seeds per m from a density of one weed every 10 m of crop row. These data suggest that using single-year economic thresholds for barnyardgrass is not a sound management practice because even low densities can produce large quantities of seed.

Barnyardgrass inflorescence length ranged from less than 2 to over 20 cm. Inflorescences less than 4 cm long were a single first-order raceme, while the largest had 20 to 50 primary branch racemes. Inflorescences longer than about 12 cm and with more than about 12 racemes showed second-order branching. Air-dried structural biomass increased from less than 2 milligrams for the smallest to over 300 milligrams for the largest inflorescences. Inflorescence length and structural biomass were positively correlated (r2 = 0.95). Floret numbers increased from about 15 for smallest inflorescences to over 2000 for largest inflorescences and were positively correlated with inflorescence length (r2 = 0.94) and with inflorescence structural biomass (r2 = 0.94). Biomass of caryopses plus aborted florets had the same relationships as those for floret number. Measurement of frequency distribution of size and determination of numbers of inflorescences per plant should provide a means to predict fecundity in barnyardgrass.

Seed size and weight significantly affected witchweed [Striga asiatica (L.) Kuntze = S. lutea Lour. ♯4 STRLU] seed germination, witchweed emergence, and host-parasitization. Witchweed seed were divided into four groups for testing; large (> 149 microns in diameter) and heavy (specific gravity greater than one) (LH), large and light (specific gravity less than one) (LL), small (< 125 microns in diameter) and heavy (SH), and small and light (SL). Germination percentages were 87, 84, 58, and 26 for LH, LL, SH, and SL, respectively. Corn (Zea mays L.) was planted in pots containing soil infested with these four seed categories. The total number of witchweed plants (submerged plus emerged) per pot containing LH, LL, SH, and SL witchweed seed was 65, 12, 0, and 0, respectively, and the number of witchweed plants that emerged was 19, 4, 0, and 0 per pot. There were no significant differences in shoot weights of corn grown in the pots either between kinds of witchweed seed infesting the soil or between plants grown in infested soil and plants grown in soil that did not contain witchweed seed. Roots of corn plants grown in soil infested with LH seed were significantly heavier than those grown in soil infested with any other seed class and heavier than those from soil that did not contain witchweed seed. No other seed class significantly affected root weight.

Crystallization of methyl m-hydroxycarbanilate m-methyl-carbanilate (phenmedipham) occurred from aqueous emulsions of the commercial formulation when dilutions exceeded one part of the formulation to 30 parts water. Dilutions greater than 1 to 30 accelerated crystallization and increased the quantity of phenmedipham that crystallized out. Mechanical agitation increased the rate of crystallization during the first 12 hr after initial mixing. Low water temperature increased the rate of crystallization and total amount of phenmedipham that crystallized out. Phenmedipham crystallization was not altered by water hardness or pH over the range 4.0 to 8.0. Simulated refilling of a partially empty spray tank before adding formulated phenmedipham produced considerable crystallization, whereas adding formulated phenmedipham before adding water minimized crystallization. The solvent used in the commercial formulation to dissolve phenmedipham is partially soluble in water. The partitioning of this solvent into the aqueous phase of the emulsion explains crystallization of phenmedipham.

Weeds and native plants should be considered when endeavoring to manage and control plant pathogens of cultivated plants. Whether as a pest itself, vector of a pathogen, or reservoir of a pathogen or its vector, weeds can significantly influence disease incidence. The relationship between these factors plays a critical role in determining disease incidence and impact. Weeds can interact with pathogen management in several ways, including provision of weed biological control, parasitic weeds can directly serve as vectors of plant pathogens, weeds can serve as reservoir alternative hosts for pathogens and vectors, weeds may be obligate alternate hosts for some pathogens, and herbicides used for weed control can interact with plant pathogens. A recent concern is the advent and deployment of plants genetically engineered for pathogen resistance, raising the question of “super weeds” resulting from genetic drift of genes from crops into surrounding weed populations, the impact of which has yet to be determined.

The need for long-term agricultural research is generally recognized. However, most long-term experiments have been designed to evaluate effects of fertility and crop rotation. Much of the current research in weed biology and weed management is conducted on a short-term basis that does not address adequately the long-term aspects of weed population ecology. In recent decades, a number of long-term experiments have been initiated to investigate the effects of both agronomic and weed management practices on weed communities. Knowledge of the existence of these experiments and the information being obtained from them are not always readily available. The Symposium held at the 2002 WSSA annual meeting in Reno, Nevada, had several goals: (1) to provide WSSA members, and other researchers, with information about long-term experiments that are currently ongoing, or recently terminated, that are investigating weed ecology and weed management; (2) to provide an exchange of ideas between researchers involved in long-term weed ecology research; (3) to provide examples of protocols and problems associated with conducting long-term weed ecology research; (4) to evaluate the scientific principles that have been, or may be, added to the discipline of weed science; and (5) to provide funding agencies with examples of how long-term weed management experiments clarify impacts of weeds in relation to sustainable agriculture.

Velvetleaf growth and canopy architecture were compared under a range of light conditions representative of competitive and noncompetitive environments typical of irrigated Mediterranean-type agroecosystems. Velvetleaf biomass and seed production exceeded those reported in the literature. Plants grown in full light produced 1,370 g dry weight and 44,200 seeds per plant and showed low relative variability. Velvetleaf grown with corn was reduced to 21 g dry weight and 349 seeds per plant, and had high relative variability for biomass and seed numbers. Velvetleaf grown with kidney bean, intraspecific neighbors, or under shadecloth had dry weights and seed numbers that were intermediate to plants grown in full light or with corn. Relative growth rate (RGR), net assimilation rate (NAR), and leaf area ratio (LAR) were assessed utilizing Richards functions, which were fitted to the primary biomass and leaf area data by weighted regression. RGR was highest for all plants early in the season, but declined later. Dynamics of NAR and LAR appeared to be correlated with increased self-shading, shading by neighbors, leaf age, and shedding of lower canopy leaves. Dynamics of specific leaf area corresponded with light availability such that the leaves exposed to full light were thicker than those exposed to shade. The branches of plants in all treatments had random azimuths and the foliage area density was concentrated along the perimeter of the plant's canopy. Velvetleaf increased the canopy radius through extensive branching when exposed to full sunlight. Leaf area distribution and branching patterns resulted in leaf area indices of less than 1.0. Leaves maintained a perpendicular angle to the sun throughout the day, but this depended on whether leaves received a consistent directional signal from the sun and not necessarily on whether they received a high-intensity signal. When shaded, the allocation of dry matter went primarily to the stem tissue, which increased the height rather than the girth of the plants. There was a 10- to 20-d delay for allocations to seed in the case of shaded plants relative to those grown in full sunlight. In brief, velvetleaf had a wide range of growth and canopy responses to a variety of light availabilities and it should have little difficulty in becoming fully established in the irrigated agroecosystems of Mediterranean-type regions.

Interactions between weeds and arthropods occur frequently. This review covers the topic of weed/arthropod interactions, and provides the reader with access to literature in the subject area that is scattered in weed science, entomological, crop production, and ecological journals. We first analyze the current status of weed and arthropod management in the context of multidisciplinary integrated pest management (IPM). The remainder of the review is organized according to the mechanisms driving interactions. The first section deals with interactions driven by trophic relationships, and is subdivided into direct and indirect trophic interactions. Direct trophic interactions occur when pest or beneficial arthropods feed directly on weeds. Indirect trophic interactions occur when arthropod feeding damage to crops impacts weeds through alteration of ecosystem resource availability, or through weeds serving as hosts for alternate prey for beneficial arthropods, or via tritrophic interactions. The second mechanism driving interactions is considered in relation to alteration of the physical habitat by the presence of weeds, such as alteration of temperature within the plant canopy. The third major mechanism driving interactions is based on control tactics for the two types of pests. These are considered from the aspect of direct physical effects, such as tillage, and from the aspect of interactions resulting from the use of pesticides. The latter is divided into direct effects of herbicides and insecticides on non-target pests and beneficials, and on interactions that result from alteration of host plant physiology by pesticides. A conclusion section attempts to place the impact of interactions into an IPM framework, and to indicate where multidisciplinary research involving weed and arthropod management should be focused in the future.