Nanoparticles: Properties and Applications in Cancer Immunotherapy.

BACKGROUND: Tumours are no longer regarded as isolated masses of aberrantly proliferating epithelial cells. Rather, their properties depend on complex interactions between epithelial cancer cells and the surrounding stromal compartment within the tumour microenvironment. In particular, leukocyte infiltration plays a role in controlling tumour development and is now considered one of the hallmarks of cancer. Thus, in the last few years, immunotherapy has become a promising strategy to fight cancer, as its goal is to reprogram or activate antitumour immunity to kill tumour cells, without damaging the normal cells and provide long-lasting results where other therapies fail. However, the immune-related adverse events due to the low specificity in tumour cell targeting, strongly limit immunotherapy efficacy. In this regard, nanomedicine offers a platform for the delivery of different immunotherapeutic agents specifically to the tumour site, thus increasing efficacy and reducing toxicity. Indeed, playing with different material types, several nanoparticles can be formulated with different shape, charge, size and surface chemical modifications making them the most promising platform for biomedical applications. AIM: In this review, we will summarize the different types of cancer immunotherapy currently in clinical trials or already approved for cancer treatment. Then, we will focus on the most recent promising strategies to deliver immunotherapies directly to the tumour site using nanoparticles. CONCLUSION: Nanomedicine seems to be a promising approach to improve the efficacy of cancer immunotherapy. However, additional investigations are needed to minimize the variables in the production processes in order to make nanoparticles suitable for clinical use.

The Evolution of a Process for Selecting and Prioritizing Plant Diseases for Recovery Plans.

One element of the cost of dealing with invasive species in the United States is the recovery from the arrival of exotic plant pathogens. We review the development of a process used to prioritize plant diseases for the federally mandated United State Department of Agriculture National Plant Disease Recovery System. A team of university, government, and industry scientists worked together over a 10-year period to develop a science-based objective approach to the challenge of effectively preparing for recovery plans from introduced pathogens, when the timing of the introduction of any single disease is unknown. Over time, the process transitioned from ad hoc, in which recovery plans were written when the relevant experts were able to do so, to a formally organized group-prioritization effort from which emerged the concept of generic recovery plan templates for groups of pathogens and diseases that have similar biological characteristics, and therefore, similar management approaches. Key characteristics for each template were determined through a multivariate analysis for 14 plant diseases for which a recovery plan already existed. The process was validated by a larger group of 15 plant pathologists, for which results were compared with those scored by 14 subject matter experts.

Oestrogen receptor positive breast cancer metastasis to bone: inhibition by targeting the bone microenvironment in vivo.

Clinical trials have shown that adjuvant Zoledronic acid (ZOL) reduces the development of bone metastases irrespective of ER status. However, post-menopausal patients show anti-tumour benefit with ZOL whereas pre-menopausal patients do not. Here we have developed in vivo models of spontaneous ER+ve breast cancer metastasis to bone and investigated the effects of ZOL and oestrogen on tumour cell dissemination and growth. ER+ve (MCF7, T47D) or ER-ve (MDA-MB-231) cells were administered by inter-mammary or inter-cardiac injection into female nude mice ± estradiol. Mice were administered saline or 100 µg/kg ZOL weekly. Tumour growth, dissemination of tumour cells in blood, bone and bone turnover were monitored by luciferase imaging, histology, flow cytometry, two-photon microscopy, micro-CT and TRAP/P1NP ELISA. Estradiol induced metastasis of ER+ve cells to bone in 80-100 % of animals whereas bone metastases from ER-ve cells were unaffected. Administration of ZOL had no effect on tumour growth in the fat pad but significantly inhibited dissemination of ER+ve tumour cells to bone and frequency of bone metastasis. Estradiol and ZOL increased bone volume via different mechanisms: Estradiol increased activity of bone forming osteoblasts whereas administration of ZOL to estradiol supplemented mice decreased osteoclast activity and returned osteoblast activity to levels comparable to that of saline treated mice. ER-ve cells require increased osteoclast activity to grow in bone whereas ER+ve cells do not. Zol does not affect ER+ve tumour growth in soft tissue, however, inhibition of bone turnover by ZOL reduced dissemination and growth of ER+ve breast cancer cells in bone.

Human breast cancer bone metastasis in vitro and in vivo: a novel 3D model system for studies of tumour cell-bone cell interactions.

Bone is established as the preferred site of breast cancer metastasis. However, the precise mechanisms responsible for this preference remain unidentified. In order to improve outcome for patients with advanced breast cancer and skeletal involvement, we need to better understand how this process is initiated and regulated. As bone metastasis cannot be easily studied in patients, researchers have to date mainly relied on in vivo xenograft models. A major limitation of these is that they do not contain a human bone microenvironment, increasingly considered to be an important component of metastases. In order to address this shortcoming, we have developed a novel humanised bone model, where 1 × 10(5) luciferase-expressing MDA-MB-231 or T47D human breast tumour cells are seeded on viable human subchaodral bone discs in vitro. These discs contain functional osteoclasts 2-weeks after in vitro culture and positive staining for calcine 1-week after culture demonstrating active bone resorption/formation. In vitro inoculation of MDA-MB-231 or T47D cells colonised human bone cores and remained viable for <4 weeks, however, use of matrigel to enhance adhesion or a moving platform to increase diffusion of nutrients provided no additional advantage. Following colonisation by the tumour cells, bone discs pre-seeded with MDA-MB-231 cells were implanted subcutaneously into NOD SCID mice, and tumour growth monitored using in vivo imaging for up to 6 weeks. Tumour growth progressed in human bone discs in 80 % of the animals mimicking the later stages of human bone metastasis. Immunohistochemical and PCR analysis revealed that growing MDA-MB-231 cells in human bone resulted in these cells acquiring a molecular phenotype previously associated with breast cancer bone metastases. MDA-MB-231 cells grown in human bone discs showed increased expression of IL-1B, HRAS and MMP9 and decreased expression of S100A4, whereas, DKK2 and FN1 were unaltered compared with the same cells grown in mammary fat pads of mice not implanted with human bone discs.

Bean pod mottle virus Time of Infection Influences Soybean Yield, Yield Components, and Quality.

Bean pod mottle virus (BPMV) negatively affects soybean yield and quality, yet quantitative information on effect of time of BPMV infection on soybean yield and quality has not been reported. The impact of time of BPMV infection on soybean yield, yield components, and grain quality components were quantified during the 2006 and 2007 soybean growing seasons in Iowa. Soybean quadrats (30 cm in length) were established within soybean plots ('NB3001') that consisted of six rows and were 7.5 m long. Quadrats were sampled 9 times during the 2006 growing season and 10 times during the 2007 growing season, beginning 25 days after planting in both years. Sap was extracted from leaflet samples from each quadrat and tested for the presence or absence of BPMV by enzyme-linked immunosorbent assay. The day of year (DOY) and quadrat position when BPMV was first detected within each plot were recorded and mapped. Soybean yield, number of pods per plant, number of seed per pod, and 100-seed weight for each quadrat were determined. The relationship between time (DOY) of BPMV infection and soybean yield, soybean yield components, and soybean grain quality were then quantified using linear regression. DOY of BPMV infection within quadrats explained 89.7 and 57.9% of the variation in soybean grain yield in 2006 and 2007, respectively. Soybean yield damage functions (slopes) were 15.2 and 8.1 kg/ha per day, respectively, indicating that, for each day that BPMV infection was delayed, soybean yield increased by 15.2 kg/ha in 2006 and 8.1 kg/ha in 2007. The number of pods per plant increased by 0.15 pods for each day that BPMV infection was delayed (R2 = 72.8%) in 2006 but there was no relationship in 2007. The 100-seed weight had a significant linear relationship with the DOY when BPMV was first detected within quadrats in 2006 (slope = 0.013, R2 = 86.3%) but not in 2007. The percentage of mottled seed in 2006 decreased by 1% for each day that BPMV infection was delayed in 2006 (R2 = 87.4%). Both protein and oil content were affected by the DOY that BPMV was first detected within quadrats in 2006 but not in 2007. This study demonstrated that time of BPMV infection can negatively affect soybean yield, yield components, and grain quality components when BPMV disease risk is high.

Evaluation of Sampling and Testing Efficiencies of Plum pox virus Eradication Programs in Pennsylvania and Ontario.

Plum pox virus (PPV) was first detected in the United States in Pennsylvania in 1999 and in Ontario, Canada in 2000. Following a 10-year survey and eradication program, PPV was officially declared eradicated in Pennsylvania in 2009. Although incidence of PPV was greatly reduced from 2000 to 2008, PPV remains present in Ontario. The objective of this study was to compare how the Pennsylvania and Ontario PPV eradication programs affected the probability of detecting PPV at the leaf, scaffold, tree, and Prunus orchard block scales. A simulation model was developed to evaluate the sampling and testing efficiency of the two programs. At the tree scale, the Pennsylvania sampling and detection protocols had a detection efficiency of 71.8% compared with 40.5% for the Ontario program. Several components in the Pennsylvania and Ontario PPV eradication programs affected PPV detection efficiency. A stratified (by tree scaffold) random sampling design did not improve PPV detection efficiency in either program, compared with a simple random sampling design to select leaves for enzyme-linked immunosorbent assay (ELISA) testing. Detection efficiency for both programs increased with sample size but gains in detection efficiency diminished as sample size increased. There was good agreement (between the commercial ELISA kit used in Pennsylvania and the kit used in Ontario) at the leaf and scaffold scales but not the tree scale. Based on simulation modeling, the Pennsylvania PPV eradication program required that >2 PPV-positive trees must be present within a Prunus block to achieve a 95% probability of correctly detecting PPV at the block scale, whereas the Ontario program required >5 PPV-positive trees within a block to achieve 95% probability of detection. The results from this study have important implications with regard to the efficiency of the two eradication programs to detect PPV-positive trees.

Impact of Eradication Programs on the Temporal and Spatial Dynamics of Plum pox virus on Prunus spp. in Pennsylvania and Ontario, Canada.

The goals of this research were to quantify the impacts of the Pennsylvania and Ontario Plum pox virus (PPV) eradication programs on the spatial and temporal dynamics of PPV epidemics on Prunus spp. The incidence of PPV-positive trees detected over time decreased in both Pennsylvania (-ln 0.85 units per year) and Ontario (-ln 0.51 units per year); however, PPV incidence per year decreased only 60% as fast in Ontario as in Pennsylvania. Marked point pattern analysis revealed that PPV-positive Prunus blocks in Pennsylvania were clustered for distances of 0.7 to 4.3 km, whereas PPV-positive blocks in Ontario were clustered for distances of 1.0 to 25.0 km. Multiyear spatiotemporal analyses revealed that the locations of PPV-positive blocks detected were spatially dependent upon the locations of PPV-positive blocks detected during the previous year. In Pennsylvania, between 2002 and 2006, distances to 95% of newly detected PPV-positive blocks occurred within 10 and 20 km from the previous year's PPV-positive blocks. In Ontario, 95% of new PPV-positive blocks occurred within 500 to 900 m from PPV-positive blocks detected the previous year. Until 2011, the PPV eradication policy for Prunus blocks in Ontario was triggered by a threshold incidence or PPV-positive tests for three consecutive years. Although the Ontario program was highly successful in reducing PPV incidence from 2001 to 2008, PPV was not eradicated. This study provides important quantitative information concerning the impact of PPV eradication programs on the spatial and temporal dynamics of PPV epidemics in Pennsylvania and Ontario. The analyses employed in this study may help to improve the effectiveness of present and future PPV eradication programs.

Geospatial and temporal analyses of Bean pod mottle virus epidemics in soybean at three spatial scales.

A statewide survey was carried out from 2005 through 2007 to quantify, map, and analyze the spatial dynamics and seasonal patterns of Bean pod mottle virus (BPMV) prevalence and incidence within Iowa. In all, 8 to 16 soybean fields were arbitrarily sampled from 96 counties in 2005 and all 99 counties in 2006 and 2007. Field- and county-scale BPMV prevalence and incidence data were mapped using geographic information systems software. BPMV prevalence was highest in the 2006 soybean growing season, when BPMV was detected in 38.7% of all soybean fields, 91.9% of all counties, and 100% of the agricultural climate districts. BPMV incidence at the field scale was highest in 2006, when mean statewide end-of-season incidence was 24.4%. Spatial analyses indicated that BPMV incidence was spatially clustered at the county scale in all three growing seasons. Prevalence at the county scale was clustered in 2005 and 2007 but not in 2006. Semivariogram analyses at the field scale indicated the presence of significant (P ≤ 0.05) spatial dependence (clustering) at distances ≤23.4 km in 2005, 297.7 km in 2006, and 45.2 km in 2007. Data for county-scale incidence displayed a north (low incidence) to south (high incidence) BPMV gradient in each year of the survey. High county-scale BPMV prevalence and incidence levels in 2006 were significantly associated with BPMV prevalence and incidence in 2007 (P ≤ 0.05). Soybean fields with narrow row spacings (≤38 cm) were associated with higher levels of BPMV incidence. Soybean fields infected with BPMV had a higher probability of infection by Phomopsis pod and stem blight than did non-BPMV-infected fields. This study provides new quantitative tools and information to better understand the seasonal, temporal, and geographical distribution of BPMV disease risk at several spatial scales.

Macrophages as potential targets for zoledronic acid outside the skeleton-evidence from in vitro and in vivo models.

PURPOSE: Multiple cell types of the tumour microenvironment, including macrophages, contribute to the response to cancer therapy. The anti-resorptive agent zoledronic acid (ZOL) has anti-tumour effects in vitro and in vivo, but it is not known to what extent macrophages are affected by this agent. We have therefore investigated the effects of ZOL on macrophages using a combination of in vitro and in vivo models. METHODS: J774 macrophages were treated with ZOL in vitro, alone and in combination with doxorubicin (DOX), and the levels of apoptosis and necrosis determined. Uptake of zoledronic acid was assessed by detection of unprenylated Rap1a in J774 macrophages in vitro, in peritoneal macrophages and in macrophage populations isolated from subcutaneously implanted breast cancer xenografts following ZOL treatment in vivo. RESULTS: Exposure of J774 macrophages to 5 µM ZOL for 24 h caused a significant increase in the levels of uRap1A, and higher doses/longer exposure induced apoptotic cell death. DOX (10 nM/24 h) and ZOL (10 µM/4 h) given in sequence induced significantly increased levels of apoptotic cell death compared to single agents. Peritoneal macrophages and macrophage populations isolated from breast tumour xenografts had detectable levels of uRap1A 24 h following a single, clinically achievable dose of 100 µg/kg ZOL in vivo. CONCLUSION: We demonstrate that macrophages are sensitive to sequential administration of DOX and ZOL, and that both peritoneal and breast tumour associated macrophages rapidly take up ZOL in vivo. Our data support that macrophages may contribute to the anti-tumour effect of ZOL.

Seliciclib inhibits renal hypertrophy but not fibrosis in the rat following subtotal nephrectomy.

BACKGROUND: 5/6 subtotal nephrectomy (SNx) is a non-immune stimulus used to induce renal fibrosis. The ability of seliciclib, a cyclin-dependent kinase inhibitor, to reduce kidney hypertrophy and extracellular matrix (ECM) deposition has been examined in the SNx rat. METHODS: Wistar rats were subjected to SNx under isoflurane anaesthesia. The acute effect of seliciclib 28 mg/kg (5 days) on compensatory renal growth (CRG), kidney protein and DNA was determined. In chronic studies albuminuria, hypertension and GFR were monitored. Ki67, apoptag and α-smooth muscle actin were determined by immunohistochemistry together with Masson's trichrome staining. The effect of a maximum non-hypotensive dose of seliciclib 28 mg/kg (8 weeks) was determined. RESULTS: Acutely, the remnant kidney developed CRG. Seliciclib 28 mg/kg inhibited both CRG by 45% and increased kidney protein by 48% without affecting increased kidney DNA. Chronically, SNx rats developed albuminuria, hypertension, low GFR with increased tubulointerstitial cell proliferation, apoptosis, myofibroblast accumulation and enhanced ECM deposition. Seliciclib 28 mg/kg (8 weeks) had no effect on either renal function or renal pathology. Plasma concentrations of seliciclib exceeded 5 µM throughout the study. CONCLUSIONS: Despite inhibition of early renal hypertrophy, a maximum non-hypotensive dose of seliciclib 28 mg/kg had no impact on the progression of kidney fibrosis in the SNx rat.

Quantifying the Within-Field Temporal and Spatial Dynamics of Bean pod mottle virus in Soybean.

The prevalence and incidence of Bean pod mottle virus (BPMV) have been reported to be on the increase in the United States but little is known about the temporal and spatial dynamics of this virus within soybean (Glycine max) fields. A quadrat-based sampling method was developed to quantify the within-field spread of BPMV in soybean in 2006 and 2007. Twenty-five 30-cm-long quadrats were established within each row of soybean in field plots consisting of six rows, each 7.6 m long and spaced 0.76 m apart. Four treatments were used to influence the temporal and spatial dynamics of BPMV epidemics. Treatments were: (i) establishment of a point source of BPMV inoculum within soybean plots; (ii) lambda-cyhalothrin insecticide applied at the V1 and R2 growth stages; (iii) establishment of a BPMV inoculum point source, plus the application of foliar insecticide sprays at the V1 and R2 growth stages; and (iv) a nontreated, noninoculated control. All quadrats (census) were sampled beginning 25 days after planting; sampling continued every 8 to 11 days until plants were senescent. Sap from leaf samples was extracted and tested for BPMV by enzyme-linked immunosorbent assay. The incidence of BPMV per treatment was plotted against time to produce BPMV incidence curves for temporal analyses. In addition, positions of BPMV-positive quadrats were mapped for spatial analyses. BPMV was detected within soybean plots on the first sampling date in 2006 (30 May) and on the second sampling date in 2007 (21 June). The rate of BPMV temporal spread within treatments ranged from 0.11 to 0.13 logits/day in 2006 and from 0.05 to 0.07 logits/day in 2007. Doubling times for BPMV incidence among treatments ranged from 5.4 to 6.4 days in 2006 and from 10.0 to 14.1 days in 2007. Soybean plots that had the earliest dates of BPMV detection within quadrats (x) also had the highest BPMV incidence (y) at the end of the growing season (R2 = 66.5 and 70.4% for 2006 and 2007, respectively). Spatial analyses using ordinary runs, black-white join-counts, and spatial autocorrelation revealed highly aggregated spatial patterns of BPMV-infected quadrats over time. Bean leaf beetle population densities were linearly related to BPMV incidence (P < 0.0001) in both years, indicating that BPMV epidemics were greatly influenced by bean leaf beetle population density. To our knowledge, this is the first study to quantify the seasonal temporal and spatial dynamics of BPMV spread within soybean.

Prevalence, incidence, and spatial dependence of soybean mosaic virus in Iowa.

The prevalence of soybean fields with plants infected with Soybean mosaic virus (SMV) in Iowa is assumed to be random, because the primary source of the virus is SMV-infected seed. Data collected from 2,500 soybean fields sampled over a 3-year period as part of the Iowa Soybean Disease Survey (2005 to 2007) were used to evaluate this assumption. SMV was first detected in early June of each year but counties in which it was first detected varied among years. Prevalence at the county scale at end of season was 32.3, 27.3, and 89.9% in 2005, 2006, and 2007, respectively. End-of-season incidence of SMV within SMV-positive counties was 1.5 to 25.0, 1.7 to 24, and 1.8 to 58% in 2005, 2006, and 2007, respectively. The number of fields in which plants infected with SMV were detected increased at the linear rate of approximately one new field every 2 days in 2007, compared with one new field every 22 days (2005) and 21 days (2006), with coefficients of determination (R2) of 93.2 to 96.8% using the linear model. Weak spatial dependence for end-of-season SMV incidence was detected using Moran's Index, indicating that the risk for SMV incidence at the county scale within Iowa at the end of the growing season is not random.

Evaluating the Importance of Stem Canker of Soybean in Iowa.

The relative importance of stem canker of soybean in Iowa compared with other soybean diseases present in the state was assessed using data collected from over 3,400 soybean fields sampled in the Iowa Soybean Disease Survey that was conducted from 2005 to 2007. Symptomatic plant tissues from soybean plants with stem canker symptoms were cultured on acidified potato dextrose agar. The prevalence of stem canker on soybean in 2005 in Iowa was 2.6%; the disease was not detected in 2006 and 2007. In 2005, 63 isolates with Diaporthe/Phomopsis characteristics were collected. To identify isolates to fungal species and variety, single-spored isolates were subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing of the internal transcribed spacer (ITS) region. Fourteen isolates were identified as D. phaseolorum var. caulivora (northern stem canker) and 49 as Phomopsis longicolla. To quantify and compare the aggressiveness of D. phaseolorum var. caulivora isolates collected in Iowa, nine isolates were arbitrarily selected for components analysis. Incubation period, rate of lesion expansion, final lesion length, and time to plant death for each isolate were quantified. Significant differences in components of aggressiveness were detected among the nine isolates. Results from this work suggest stem canker is a minor disease of soybean in Iowa.

Comparison of Models for Forecasting of Stewart's Disease of Corn in Iowa.

Three forecasting models for Stewart's disease (Pantoea stewartii subsp. stewartii) of corn (Zea mays) were examined for their ability to accurately predict the prevalence of Stewart's disease in Iowa at the county level. The Stevens Model, which is used as a predictor of the early wilt phase of Stewart's disease, the Stevens-Boewe Model, which predicts the late leaf blight phase of Stewart's disease, and the Iowa State Model that is used to predict the prevalence of Stewart's disease, all use mean air temperatures for December, January, and February for a preplant prediction of Stewart's disease risk in a subsequent season. Models were fitted using weighted binary logistic regression with Stewart's disease prevalence data and air temperature data for 1972 to 2003. For each model, the years 1972 to 1999 (n = 786 county-years) were used for model development to obtain parameter coefficients. All three models indicated an increased likelihood for Stewart's disease occurring in growing seasons preceded by warmer winters. Using internal bootstrap validation, the Stevens Model had a maximum error between predicted and calibrated probabilities of 10%, whereas the Stevens-Boewe and Iowa State models had maximum errors of 1% or less. External validation for each model, using air temperature and seed corn inspection data between 2000 and 2003 (n = 154 county-years), indicated that overall accuracy to predict Stewart's disease at the county level was between 62 and 66%. However, both the Stevens and Stevens-Boewe models were overly optimistic in predicting that Stewart's disease would not occur within specific counties, as the sensitivity for these two models was quite low (18 and 43%, respectively). The Iowa State Model was substantially more sensitive (67%). The results of this study suggest that the Iowa State Model has increased predictive ability beyond statewide predictions for estimating the risk of Stewart's disease at the county level in Iowa.

Quantifying the Feeding Periods Required by Corn Flea Beetles to Acquire and Transmit Pantoea stewartii.

The feeding periods required by corn flea beetles to acquire and transmit Pantoea stewartii were investigated in the Stewart's disease of corn pathosystem. To quantify the effect of acquisition feeding period on percentage of acquisition, field-collected corn beetles were allowed to feed for 6, 12, 24 36, 48, and 72 h on corn seedlings previously inoculated with a rifampicin- and nalidixic acid-restraint strain of P. stewartii. Acquisition of P. stewartii by corn flea beetles was considered positive if the rifampicin- and nalidixic acid-marked strain was recovered on selective media. To quantity the effect of transmission feeding period on percent transmission of P. stewartii by corn flea beetles, P. stewartii- infested corn flea beetles were allowed to feed on healthy corn seedlings for periods of 3, 6, 12, 24, 36, 48, and 72 h. After the appropriate transmission feeding period, leaf tissues surrounding the sites of feeding scars were cultured for the presence of the P. stewartii-marked strain. Transmission of P. stewartii was considered positive if the marked strain was recovered on selective media. Acquisition of P. stewartii occurred within 6 h and the percentage of corn flea beetles that had acquired P. stewartii after 72 h ranged from 68 to 94%. The change in P. stewartii acquisition by corn flea beetles (Y) with respect to acquisition feeding period (X) was best described by the Gompertz model, with R2 values ranging from 91 to 99%. The mean time for acquisition by 50% of the corn flea beetles was 36.5 ± 11.6 h. The minimum transmission feeding time required for corn flea beetles to transmit P. stewartii following a 48-h acquisition feeding period was less than 3 h. The percent transmission of P. stewartii by corn flea beetles was nearly 100% after a 48-h transmission feeding period and was 100% by 72 h. Among population growth models evaluated, the monomolecular model best described the relationship between percent transmission (Y) and transmission feeding periods (X), with R 2 values of up to 84%. However, a nonlinear form of the monomolecular model better quantified the relationship between percent transmission and transmission feeding period, because pseudo-R2 values ranged between 98.1 and 99.5%. The predicted transmission feeding time required for 50% of P. stewartii-infested corn flea beetles to transmit the pathogen was 7.6 ± 0.87 h. These results suggest that the corn flea beetle is a highly efficient vector that can quickly acquire and transmit P. stewartii, thereby requiring insecticide seed treatments and foliar insecticides that act quickly to prevent corn flea beetles from acquiring and transmitting P. stewartii to corn plants.

Population densities of corn flea beetle (Coleoptera: Chrysomelidae) and incidence of Stewart's wilt in sweet corn.

To quantify populations of the corn flea beetle, Chaetocnema pulicaria Melsheimer (Coleoptera: Chrysomelidae), and refine estimates of a threshold for its control to prevent Stewart's wilt caused by Erwinia stewartii, sequential plantings of 'Jubilee' sweet corn were made at 2-wk intervals from April or May through August or September 2001 and 2002 at four locations from southern to northern Illinois: Simpson, Brownstown, Champaign, and Mendota. Densities of C. pulicaria and incidence of Stewart's wilt were monitored weekly. At Mendota, where C. pulicaria populations were decimated by cold temperatures during winter 2000-2001, densities reached 33.3 beetles per 15-cm yellow sticky trap per day by September 2002, after a mild 2001-2002 winter. Maximum incidence of Stewart's wilt in single plots at Simpson, Brownstown, Champaign, and Mendota was 22, 36, 39, and 2%, respectively, in 2001, and 33, 47, 99, and 87%, respectively, in 2002. In 24 plots where beetle densities were < or =2 per trap per day, Stewart's wilt incidence was <5% in 20 plots. We propose that two corn flea beetles per trap per day be used as a threshold for insecticide application to seedlings to control C. pulicaria and minimize subsequent incidence of Stewart's wilt in processing sweet corn. Enzyme-linked immunosorbent assays indicated that E. stewartii incidence in C. pulicaria peaked at 67, 62, and 54%, respectively, at Simpson, Brownstown, and Champaign, in 2001, and at 71, 76, and 60%, respectively, in 2002. Further studies might allow the use of areawide or field-specific estimates of E. stewartii incidence in corn flea beetles for adjusting management decisions.

Trap height and orientation of yellow sticky traps affect capture of Chaetocnema pulicaria (Coleoptera: Chrysomelidae).

Field studies were conducted in Iowa during 2001 and 2002 to determine the optimal sampling height and orientation for using yellow sticky cards to monitor populations of Chaetocnema pulicaria Melsheimer, the vector of the bacterial pathogen Pantoea stewartii subsp, stewartii, the causal organism of Stewart's disease of corn, Zea mays L.. Sticky cards were placed at five different heights (0.15, 0.30, 0.45, 0.60, and 0.90 m) and three orientations (horizontal, vertical, and 30 degree angle) at three locations (Ames, Crawfordsville, and Sutherland) in 2001 and two locations (Crawfordsville and Johnston) in 2002. No statistical differences were observed among the placement combinations for individual sampling periods or for the total number of C. pulicaria captured in 2001. In 2002, the 0.30 m and vertical cards captured significantly (1.1-35 times) more C. pulicaria than any other placement combination during sampling throughout August at both Crawfordsville and Johnston. Also, the cumulative number of C. pulicaria captured by the 0.30 m and vertical cards was significantly higher than all other placement combinations. This information is important in the development of sampling protocols to aid growers in making management decisions. These management decisions include where and when to apply foliar insecticides during the corn growing season to control C. pulicaria populations, thereby reducing the risk for Stewart's disease of corn.

Temporal Dynamics of Corn Flea Beetle Populations Infested with Pantoea stewartii, Causal Agent of Stewart's Disease of Corn.

ABSTRACT In order to better understand the epidemiology of the Stewart's disease of corn pathosystem, quantitative information concerning the temporal dynamics of the amount of pathogen inoculum present in the form of Pantoea stewartii-infested corn flea beetles (Chaetocnema pulicaria) is needed. Temporal changes in the proportion of P. stewartii-infested corn flea beetle populations were monitored by testing individual corn flea beetles for the presence of P. stewartii using a peroxidase-labeled, enzyme-linked immunosorbent assay. Approximately 90 corn flea beetles were collected each week from seven locations in Iowa from September 1998 through October 2000 using sweep nets. The proportion of P. stewartii-infested beetles at the end of the 1998 growing season ranged from 0.04 to 0.19. In spring 1999, the proportion of overwintering adult corn flea beetles infested with P. stewartii ranged from 0.10 to 0.11 and did not differ significantly from the previous fall based on chi(2). During the 1999 corn-growing season, the proportion of infested corn flea beetles ranged from 0.04 to 0.86, with the highest proportions occurring in August. In fall 1999, the proportion of beetles infested with P. stewartii ranged from 0.20 to 0.77. In spring 2000, the proportion of overwintering adult corn flea beetles infested with P. stewartii ranged from 0.08 to 0.30; these proportions were significantly lower than the proportions observed in fall 1999 at Ames, Chariton, and Nashua. During the 2000 corn-growing season, the proportion of P. stewartii-infested corn flea beetles ranged from 0.08 to 0.53, and the highest observed proportions again occurred in August. Corn flea beetle populations sampled in late fall 2000 had proportions of infested beetles ranging from 0.08 to 0.20. This is the first study to quantify the temporal population dynamics of P. stewartii-infested C. pulicaria populations in hybrid corn and provides new quantitative information that should be useful in developing risk models to predict the seasonal and site-specific risks associated with Stewart's disease of corn.

Strawberry Plant Extracts Stimulate Secondary Conidiation by Colletotrichum acutatum on Symptomless Leaves.

ABSTRACT Conidial suspensions of Colletotrichum acutatum were prepared in 1:27, 1:45, and 1:81 (wt/vol) dilutions of an extract of strawberry (cv. Tristar) flowers or leaves in water. Strawberry leaves and plastic coverslips were sprayed with the conidial suspensions, incubated at 25 degrees C and continuous wetness for 48 h, and the number of conidia and appressoria were counted. In another experiment, leaves and coverslips were sprayed with a conidial suspension in water, incubated for 72 h to establish C. acutatum populations, and placed in a growth chamber under dry conditions for up to 6 weeks. At each sampling time, leaves and coverslips were sprayed with flower extracts, leaf extracts, or water, incubated for 48 h at 25 degrees C and continuous wetness, and the number of conidia and appressoria were counted. Flower extracts significantly (P

Influence of Temperature and Wetness Duration on Conidia and Appressoria of Colletotrichum acutatum on Symptomless Strawberry Leaves.

ABSTRACT Strawberry leaves (cv. Tristar) inoculated with Colletotrichum acuta-tum conidia were incubated at 10, 15, 20, 25, 30, and 35 degrees C under continuous wetness, and at 25 degrees C under six intermittent wetness regimes. The number of conidia and appressoria was quantified on excised leaf disks. In order to assess pathogen survival, inoculated leaves were frozen and incubated to induce acervular development. Germination, secondary3 conidiation, and appressorial development were significantly (P /= 0.95) related to appressorial populations prior to this treatment and was greatest following periods of continuous wetness. Production of secondary conidia and appressoria of C. acutatum on symptomless strawberry leaves under a range of environmental conditions suggests that these processes also occur under field conditions and contribute to inoculum availability during the growing season.