Agricultural Science Commons^™

On-Farm Evaluation Of Tomato Cultivars For Disease Resistance, 2006, Dan Egel, Butch Zandstra, Elizabeth T. Maynard

Purdue Fruit and Vegetable Research Reports

Bacterial spot of tomatoes (Xanthomonas campestris pv. vesicatoria) causes lesions on leaves, stems and fruit. Under conditions of hot, humid, rainy weather, defoliation can result in a loss of yield. In addition, lesions on fruit result in a direct loss of marketability. This disease is managed primarily with applications of fixed copper bactericides, crop rotations, greenhouse sanitation and healthy seed/transplants. Even in properly managed commercial fields, however, bacterial spot can cause yield losses. Although there are no varieties with complete resistance to bacterial spot, we report here the results of an on-farm trial that indicates some varieties may have partial …

Supersweet Sweet Corn Cultivar Evaluation For Northern Indiana, 2006, Elizabeth T. Maynard

Purdue Fruit and Vegetable Research Reports

The Indiana Agricultural Statistics Service reported sweet corn for fresh market sales was harvested from 5,200 acres in Indiana in 2005 and had a total value of $7.6 million. Sweet corn fields are located throughout the state. In Northern Indiana bicolor corn is most commonly grown. Varieties with improved eating quality are of interest to both producers and consumers. Producers are also interested in yield, ear size and appearance, and agronomic characteristics. This paper reports on twenty sh2 sweet corn cultivars known as ‘supersweet’ or ‘enhanced’ or ‘augmented supersweet’ that were evaluated at the Pinney-Purdue Ag Center, Wanatah, IN.

Comparative Staging Of Embryo Development In Chicken, Turkey, Duck, Goose, Guinea Fowl, And Japanese Quail Assessed From Five Hours After Fertilization Through Seventy-Two Hours Of Incubation, N. Sellier, J.-P. Brillard, V. Dupuy, M. R. Bakst

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Normal tables of chicken embryo development are used to define specific stages of morphogenetic progression from the first cleavage divisions through hatching. Although established for the turkey and Pekin duck, the application of the normal tables of chicken embryo development to other birds of commercial and research importance needs be examined. Chicken, turkey, Japanese quail, and Pekin duck blastoderms from oviductal eggs showed differences in the rate of development that were inversely correlated with egg size. Oviposited eggs from these and additional species (goose, Muscovy and mule ducks, and Guinea fowl) were examined after 24 to 72 h of storage …

Effect Of Fenbendazole On Turkey Semen Quality, M. R. Bakst, M. Kramer, J. Long

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Fenbendazole (FBZ) is an anthelmintic recently approved to treat and control nematode infections in growing turkeys. When administered to growing turkeys there are no detrimental side effects. However, when we used FBZ to treat nematodes in mature breeder toms, we observed a decrease in semen quality and a subsequent precipitous decline in fertility to less than 20% within 6 wk of administration. An experiment was designed to determine the impact of FBZ administration on aspects of spermatogenesis and semen quality. We discovered that although sperm viability and concentration was not significantly affected by FBZ, this drug significantly reduced sperm mobility. …

Spermatogenesis In The Turkey (Meleagris Gallopavo): Quantitative Approach In Immature And Adult Males Subjected To Various Photoperiods, Jérôme Noirault, Jean-Pierre Brillard

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The objectives of this study were to identify and quantitate the germ cell populations of the testes in sexually mature male turkeys (Trial 1), determine the duration of meiosis based on BrdU labeling and stereological analyses (Trial 2), and examine the impact of various photoperiods on germinal and somatic cell populations in immature and adult males (Trial 3). In Trial 1, both testes within a male had similar stereological components (P > 0.05) for all parameters analyzed. In Trial 2, the duration of Type-1 spermatocytes and round spermatids in turkeys lasted 4.5 ± 0.5 and 2.0 ± 0.5 days, respectively. In …

Characterization Of Storage Proteins In Wild (Glycine Soja) And Cultivated (Glycine Max) Soybean Seeds Using Proteomic Analysis, Savithiry S. Natarajan, Chenping Xu, Hanhong Bae, Thomas J. Caperna, Wesley M. Garrett

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A combined proteomic approach was applied for the separation, identification, and comparison of two major storage proteins, β-conglycinin and glycinin, in wild (Glycine soja) and cultivated (Glycine max) soybean seeds. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) with three different immobilized pH gradient (IPG) strips was an effective method to separate a large number of abundant and less-abundant storage proteins. Most of the subunits of β-conglycinin were well separated in the pH range 3.0-10.0, while acidic and basic glycinin polypeptides were well-separated in pH ranges 4.0-7.0 and 6.0-11.0, respectively. Although the overall distribution pattern of the protein spots …

Separation And Identification Of Soybean Leaf Proteins By Two-Dimensional Gel Electrophoresis And Mass Spectrometry, Chenping Xu, Wesley M. Garrett, Joseph Sullivan, Thomas J. Caperna, Savithiry Natarajan

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

To establish a proteomic reference map for soybean leaves, we separated and identified leaf proteins using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS). Tryptic digests of 260 spots were subjected to peptide mass fingerprinting (PMF) by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS. Fifty-three of these protein spots were identified by searching NCBInr and SwissProt databases using the Mascot search engine. Sixty-seven spots that were not identified by MALDI-TOF-MS analysis were analyzed with liquid chromatography tandem mass spectrometry (LC-MS/MS), and 66 of these spots were identified by searching against the NCBInr, SwissProt and expressed sequence tag (EST) databases. …

The Best Dna Markers Pennies Can Buy A Specialized Set Of Cattle Markers For Improving Food Safety And Beef Quality, Michael P. Heaton

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Researchers at the U.S. Meat Animal Research Center (USMARC) in Clay Center, Nebraska are developing a set of 100 DNA markers that will provide essential genetic information for improving food safety and beef quality in North American beef and dairy cattle. This powerful set of markers has been thoroughly screened to accomplish both DNA fingerprinting and parentage testing in essentially all U.S. beef and dairy populations, an ability that only a small fraction of known DNA markers have.

One key to success has been the careful sampling of U.S. beef and dairy populations to create a test panel representing the …

Dispersal Of Boll Weevils (Coleoptera: Curculionidae) From Cotton Modules Before Ginning, Thomas W. Sappington, Mark D. Arnold, Alan D. Brashears, Megha N. Parajulee, Stanley C. Carroll, Allen E. Knutson, John W. Norman Jr.

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

We characterized the level of risk of boll weevil, Anthonomus grandis grandis Boheman, reintroduction to an eradication zone posed by dispersal from cotton modules during and after transport to the gin. Mark-release-recapture experiments in August and September in Texas indicated that most weevils disperse rapidly from the module surface, temperature permitting, unless confined under a module tarp, where most died. Nevertheless, 1-5% of released weevils were recovered alive after 24 h on the side and top surfaces of modules, representing potential dispersants. Mortality of boll weevils caged on the top surface of a module was 95-100% after 1-4 d when …

Dispersal Of Newly Eclosed European Corn Borer Adults (Lepidoptera: Crambidae) From Corn Into Small-Grain Aggregation Plots, Brendon J. Reardon, Douglas V. Sumerford, Thomas W. Sappington

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Genetically modified, insecticidal Bacillus thuringiensis (Bt) corn, Zea mays L., hybrids are used throughout the Corn Belt for European corn borer, Ostrinia nubilalis(Hübner) (Lepidoptera: Crambidae), control. To slow development of Bt corn resistance, the Environmental Protection Agency requires growers to plant a refuge. Determining the appropriate distance between a refuge and Bt corn, and development of mitigation-remediation strategies such as mass releases of susceptible moths, requires an understanding of adult dispersal and mating behavior. However, much remains unknown about these behaviors. Because mating often occurs in grass near cornfields where adult O. nubilalis aggregate, we planted small-grain plots as …

Impact Of Trap Design, Windbreaks, And Weather On Captures Of European Corn Borer (Lepidoptera: Crambidae) In Pheromone-Baited Traps, Thomas W. Sappington, Brendon J. Reardon, Douglas V. Sumerford

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Pheromone-baited traps are often used in ecological studies of the European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae). However, differences in trap captures may be confounded by trap design, trap location relative to a windbreak, and changes in local weather. The objectives of this experiment were, first, to examine differences in O. nubilalis adult (moth) captures among the Intercept wing trap, the Intercept bucket/funnel UNI trap, and the Hartstack wire-mesh, 75-cm-diameter cone trap (large metal cone trap) as well as among three cone trap designs. Second, we examined the influence of the location of the large metal cone trap relative …

Usmarc Beef Carcass Instrument Grading Systems, Tommy Wheeler, Steven Shackelford, Mohammad Koohmaraie

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Evaluation of Beef Carcass Grades with Image Analysis

Beef Tenderness

Post-Weaning Performance Of Steers From Varying Calving And Weaning Strategies In Montana, E. E. Grings, W. A. Phillips, R. E. Short, H. Mayeux, R. K. Heitschmidt

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The impact of varied calving and weaning times on post-weaning production of steer calves was evaluated in a 3- yr study. Steers (approximately 12 steers per calving-weaning treatment per year) born in late winter or early spring were weaned at 190 or 240 d of age, and steers born in late spring were weaned at 140 or 190 d of age after grazing with their dams on native range. Steers were pen-fed a growing diet until approximately 375 kg BW. They were then moved to an individual feeding facility and fed a higher-energy diet. Steers were allotted to harvest dates …

Registration Of ‘Choptank’ Wheat, J.M. Costa, C.A. Griffey, H.E. Bockelman, S.E. Cambron, X. Chen, A. Cooper, C. Gaines, Robert A. Graybosch, A. Grybauskas, R.J. Kratochvil, D.L. Long, E. Shirley, L. Whitcher

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

‘Choptank’ (Reg. no. CV-976, PI 639724) is a soft red winter wheat (Triticum aestivum L.) that was jointly developed and released by the Maryland Agricultural Experiment Station, Department of Natural Resource Sciences and Landscape Architecture, and the Virginia Agricultural Experiment Station in 2004. Choptank is named after Maryland’s longest scenic river, which flows 70 miles from the western part of Delaware through Maryland and into the Chesapeake Bay, on Maryland’s Eastern Shore. Choptank has performed well in Maryland, Virginia, and Delaware and provides growers with a high-yielding cultivar with short stature, excellent powdery mildew [caused by Blumeria graminis (DC.) …

Traps And Trapping Techniques For Adult Mosquito Control, Daniel L. Kline

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

An overview is presented of the recent advancements in research activities conducted to evaluate mosquito traps. insecticide-impregnated targets baited with combinations of attractants, and strategies for using mass trapping techniques for adult mosquito population management. Technologies that use semiochemicals (attractants). traps and targets. and mass trapping are relatively new for management of adult mosquito populations. To date. emphasis has been placed primarily on developing barriers of attractant-baited and insecticide-impregnated targets. The most successful continuous use of this type of technology has been at Stevens' Landing. Collier County. Florida, Recently. commercially available traps have been evaluated for their ability to reduce …

Androthrips Ramachandrai (Thysanoptera: Phlaeothripidae): An Introduced Thrips In The United States, David W. Boyd, Jr., David W. Held

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Androthrips ramachandrai Karny is an exotic thrips, assumed to be predacious, and is associated with gall-inducing thrips. It was first reported in the U.S. from FL, and intercepted in CA from Thailand in 2002. We surveyed Ficus spp. with Gynaikothrips-induced galls in AL, CA, FL, HI, LA, MS, and TX, and document that A. ramachandrai is now established in CA, FL, HI, and TX. It probably has been spread by the ornamental horticulture industry. We outline its biology and compare it to a congener A. flavipes, a documented thrips predator. Androthrips ramachandrai has the potential to be a …

Host Specificity Of Divergent Populations Of The Leaf Beetle Diorhabda Elongata (Coleoptera: Chrysomelidae), A Biological Control Agent Of Saltcedar (Tamarix Spp.), Lindsey R. Milbrath, C. Clark Deloach

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The leaf beetle, Diorhabda elongata (Brullé) sensu lato, was released in 2001 for the classical biological control of exotic saltcedars, a complex of invasive Tamarix species and hybrids. It did not establish at sites south of 37°N latitude where summer daylengths are below the critical photoperiod of the northern-adapted populations of the beetle that were released. Therefore, we assessed the host specificity of four D. elongata populations collected from more southern latitudes in the Old World (Tunisia, Crete, Uzbekistan, and Turpan, China). All populations were similar to each other and the previously released populations of D. elongata in their …

Prospects For Biological Control Of Teasels, Dipsacus Spp., A New Target In The United States, Brian G. Rector, Vili Harizanova, René Sforza, Tim Widmer, Robert N. Wiedenmann

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Two closely related teasels (Dipsacales: Dipsacaceae, Dipsacus spp.) of European origin have become invasive weeds in the United States. Common teasel (Dipsacus fullonum L.) and cutleaf teasel (Dipsacus laciniatus L.) have likely been in North America for more than two centuries, having been introduced along with cultivated teasel [D. sativus (L.) Honckney], an obsolete crop plant. There are few records of American insects or pathogens attacking Dipsacus spp. Invasive teasels have recently begun to spread rapidly throughout much of their current range, for reasons that are not yet known. Common and/or cut-leaf teasel have been listed as …

Rna Polymerase Ii Gene (Rpb2) Encoding The Second Largest Protein Subunit In Phaeosphaeria Nodorum And P. Avenaria, Arkadiusz Malkus, Pi-Fang Linda Chang, Sabina M. Zuzga, Kuang-Ren Chung, Jonathan Shao, Barry M. Cunfer, Edward Arseniuk, Peter P. Ueng

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A 5586 bp sequence (accession no. DQ278491), which includes the RNA polymerase II gene (RPB2) encoding the second largest protein subunit (RPB2), was obtained from the wheat biotype Phaeosphaeria nodorum (PN-w) by PCR amplification. The 3841 bp full length RPB2 gene contains two exons and a 52 bp intron, and encodes a complete 1262 amino acid protein. Similar to the C-terminals of the b subunits of prokaryotes and yeast RNA polymerases, the deduced RPB2 protein contained many structural features needed for gene transcription. Based on the phylogenetic analysis with the deduced RPB2 polypeptide sequences, the PN-w was closely related to …

Movements Of House Sparrows Captured At An Experimental Grain Station In Fargo, North Dakota, Lisa M. Montplaisir, George M. Linz, Debra Tomanek, Linda B. Penry, David L. Bergman, H. Jeffrey Homan

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

From 2 August through 1 October 1993 we banded and leg flagged 362 house sparrows (126 adults, 236 juveniles) captured in a decoy trap at an experimental grain station on the campus of North Dakota State University, Fargo (NDSU). We documented sightings of leg-flagged birds between 3 August 1993 and 14 December 1994. Over this period, 56 (66%) of the total 76 observations of leg-flagged birds were on the NDSU campus; 21 (28%) of the 76 observations occurred between March and December 1994, a minimum of 5 months after the leg flags were attached and following the 1993-1994 winter. Of …

Increasing Co2 From Subambient To Elevated Concentrations Increases Grassland Respiration Per Unit Of Net Carbon Fixation, H. Wayne Polley, Patricia C. Meilnick, William A. Dugas, Hyrum B. Johnson, Joaquin Sanabria

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Respiration (carbon efflux) by terrestrial ecosystems is a major component of the global carbon (C) cycle, but the response of C efflux to atmospheric CO₂ enrichment remains uncertain. Respiration may respond directly to an increase in the availability of C substrates at high CO₂, but also may be affected indirectly by a CO₂-mediated alteration in the amount by which respiration changes per unit of change in temperature or C uptake (sensitivity of respiration to temperature or C uptake).

Aboveground Productivity And Root–Shoot Allocation Diver Between Native And Introduced Grass Species, Brian J. Wilsey, H. Wayne Polley

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Plant species in grasslands are often separated into groups (C₄ and C₃ grasses, and forbs) with presumed links to ecosystem functioning. Each of these in turn can be separated into native and introduced (i.e., exotic) species. Although numerous studies have compared plant traits between the traditional groups of grasses and forbs, fewer have compared native versus introduced species. Introduced grass species, which were often introduced to prevent erosion or to improve grazing opportunities, have become common or even dominant species in grasslands. By virtue of their abundances, introduced species may alter ecosystems if they differ from natives in …

Partitioning Of Evapotranspiration And Its Relation To Carbon Dioxide Exchange In A Chihuahuan Desert Shrubland, Russell L. Scott, Travis E. Huxman, William L. Cable, William E. Emmerich

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Key to evaluating the consequences of woody plant encroachment on water and carbon cycling in semiarid ecosystems is a mechanistic understanding of how biological and non-biological processes influence water loss to the atmosphere. To better understand how precipitation is partitioned into the components of evapotranspiration (bare-soil evaporation and plant transpiration) and their relationship to plant uptake of carbon dioxide (CO₂) as well as ecosystem respiratory efflux, we measured whole plant transpiration, evapotranspiration, and CO₂ fluxes over the course of a growing season at a semiarid Chihuahuan Desert shrubland site in south-eastern Arizona. Whole plant transpiration was measured …

Sediment Transport Model For Seepage Erosion Of Streambank Sediment, G. A. Fox, G. V. Wilson, R. K. Periketi, R. F. Cullum

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Erosion by lateral, subsurface flow is known to erode streambank sediment in numerous geographical locations; however, the role of seepage erosion on mass failure of streambanks is not well understood. In the absence of an established sediment transport model for seepage erosion, the objectives of this research were to investigate the mechanisms of erosion due to concentrated, lateral subsurface flow and develop an empirical sediment transport model for seepage erosion of noncohesive sediment on near-vertical streambanks. Laboratory experiments were performed using a two-dimensional soil lysimeter of a reconstructed streambank profile packed with three different soil layers to mimic seepage erosion …

Estrogenic Activity In The Environment: Municipal Wastewater Effluent, River, Ponds, And Wetlands, Nancy W. Shappell

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Estrogenic activity of regional water samples was evaluated. Samples obtained from wetlands and ponds involved in various agricultural land uses, from three river sites over four seasons, and from municipal wastewater effluent held in storage lagoons were evaluated. The estrogen- responsive cell line MCF-7 BOS was used in the E-screen assay to determine 17β-estradiol equivalents (E₂ Eq) of water samples extracted by solid-phase extraction. Estrogenic activity in surrounding wetlands and ponds from different land uses was not different, with 10^-12 M E2 Eq (0.3 ppt). Estrogenic activity of Red River samples was within the same range as wetland–pond …

Net Global Warming Potential And Greenhouse Gas Intensity In Irrigated Cropping Systems In Northeastern Colorado, Arvin R. Mosier, Ardell D. Halvorson, Curtis A. Reule, Xuejun J. Liu

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The impact of management on global warming potential (GWP), crop production, and greenhouse gas intensity (GHGI) in irrigated agriculture is not well documented. A no-till (NT) cropping systems study initiated in 1999 to evaluate soil organic carbon (SOC) sequestration potential in irrigated agriculture was used in this study to make trace gas flux measurements for 3 yr to facilitate a complete greenhouse gas accounting of GWP and GHGI. Fluxes of CO₂, CH₄, and N₂O were measured using static, vented chambers, one to three times per week, year round, from April 2002 through October 2004 …

Movements Of European Starlings Captured At A Winter Roost In Omaha, Nebraska, H. Jeffrey Homan, George M. Linz, Garrett W. Unrein, James R. Thiele, John M. Hobbs

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

European starlings (Sturnus vulgaris) were using downtown Omaha, Nebraska, as a winter roosting site. We used radio telemetry and leg streamers to track birds in this roost. Between late December 2005 and March 2006, we radio tagged 57 starlings and located them 432 times. We attached leg bands and colored leg streamers to over 1,300 starlings captured at trapping sites within 7 km (4 mi) of the downtown roost. These techniques yielded data on previously unknown sites where starlings gathered to forage, stage, and roost. The maximum distance that a marked bird was observed from the downtown roost …

Nutrient Uptake Of Maize Affected By Nitrogen And Potassium Fertility In A Humid Subtropical Environment, H. Arnold Bruns, M. Wayne Ebelhar

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 0 °C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration = [ ]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant^-1 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, …

Effect Of Foliar Applied Plant Elicitors On Microbial And Nematode Populations In The Root Zone Of Potato, H. P. Collins, D. A. Navare, E. Riga, F. J. Pierce

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Systemic acquired resistance (SAR) is a process whereby a plant that successfully
resists a pathogen becomes highly resistant to subsequent infection not only by the original pathogen but also by a wide variety of pathogens. Most SAR research has focused on resistance in leaves, so much less is known about the effectiveness of foliar applications of SAR compounds in the protection of plant roots and associated microorganisms in soil. This study was conducted to determine if foliar SAR-inducing applications (BTH or harpin) negatively impact the potato root system beneficial rhizosphere microbial populations and activity or influence pathogenic nematode populations. Foliar …

Un-Ionized Ammonia Exposure In Nile Tilapia: Toxicity, Stress Response, And Susceptibility To Streptococcus Agalactiae, Joyce J. Evans, David J. Park, Gregg C. Brill, Phillip H. Klesius

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A series of experiments were conducted to determine the toxicity, behavior, blood glucose stress response, and disease susceptibility in Nile tilapia Oreochromis niloticus following un-ionized ammonia (UIA) exposure. The acute toxicity of un-ionized ammonia to Nile tilapia was measured in a 96-h static test. The median lethal concentration (LC50) was 1.46 mg/L UIA at 24 and 48 h postexposure, 1.33 mg/ L at 72 h postexposure, and 0.98 mg/L at 96 h postexposure. No mortalities were noted in unexposed (0 mg/ L) control fish or fish exposed to 0.5 mg/L UIA. However, 93–100% mortalities were observed within 24 h among …