Weather-Based Models for Assessing the Risk of Sclerotinia sclerotiorum Apothecial Presence in Soybean (Glycine max) Fields.

Sclerotinia stem rot (SSR) epidemics in soybean, caused by Sclerotinia sclerotiorum, are currently responsible for annual yield reductions in the United States of up to 1 million metric tons. In-season disease management is largely dependent on chemical control but its efficiency and cost-effectiveness depends on both the chemistry used and the risk of apothecia formation, germination, and further dispersal of ascospores during susceptible soybean growth stages. Hence, accurate prediction of the S. sclerotiorum apothecial risk during the soybean flowering period could enable farmers to improve in-season SSR management. From 2014 to 2016, apothecial presence or absence was monitored in three irrigated (n = 1,505 plot-level observations) and six nonirrigated (n = 2,361 plot-level observations) field trials located in Iowa (n = 156), Michigan (n = 1,400), and Wisconsin (n = 2,310), for a total of 3,866 plot-level observations. Hourly air temperature, relative humidity, dew point, wind speed, leaf wetness, and rainfall were also monitored continuously, throughout the season, at each location using high-resolution gridded weather data. Logistic regression models were developed for irrigated and nonirrigated conditions using apothecial presence as a binary response variable. Agronomic variables (row width) and weather-related variables (defined as 30-day moving averages, prior to apothecial presence) were tested for their predictive ability. In irrigated soybean fields, apothecial presence was best explained by row width (r = -0.41, P < 0.0001), 30-day moving averages of daily maximum air temperature (r = 0.27, P < 0.0001), and daily maximum relative humidity (r = 0.16, P < 0.05). In nonirrigated fields, apothecial presence was best explained by using moving averages of daily maximum air temperature (r = -0.30, P < 0.0001) and wind speed (r = -0.27, P < 0.0001). These models correctly predicted (overall accuracy of 67 to 70%) apothecial presence during the soybean flowering period for four independent datasets (n = 1,102 plot-level observations or 30 daily mean observations).

Optimal waiting period for foot salvage surgery following limb revascularization.

It is not clear how soon after bypass surgery tissue perfusion in the ischemic foot is adequate for healing. The purpose of this study was to determine the time interval for tissue to receive adequate oxygenation for healing following limb revascularization. Eleven patients with severe foot ischemia as defined by a transcutaneous oxygen tension (TcPO2) of 30 mm Hg or less were included in the study. TcPO2 measurements were performed prior to the lower extremity bypass and at postoperative day 1, 2, and 3. The mean preoperative value (9.27 mm Hg) was compared with the mean value at postoperative day 1 (17.73 mm Hg), postoperative day 2 (20.36 mm Hg), and postoperative day 3 (36.82 mm Hg) using paired samples t-tests. Statistically significant differences were observed between the mean preoperative TcPO2 measurement and the mean TcPO2 measurement taken on the 3rd postoperative day. The mean TcPO2 level increased from 9.27 mm Hg preoperatively to 36.82 mm Hg by the 3rd postoperative day (p = .001). There was also a statistically significant difference between the mean values on the 2nd (20.36 mm Hg) and 3rd postoperative day (36.82 mm Hg) (p = .002). Despite this finding, 5 of the 11 patients still had individual TcPO2 readings of less than 30 mm Hg on the 3rd postoperative day. Therefore, it can be concluded that in most instances tissue oxygenation reaches an adequate level after waiting at least 3 days following a bypass. Waiting 3 or more days could give adequate time for tissue reperfusion to promote healing of the surgical site.