of 120 d under ice cover without damage (Beard 1965). Total submersion in ice causes greater damage than Damage as a result of ice cover on putting greens affects golf partial submersion or ice cover only (Andrews and Pomcourses in cold climates. The objectives of this study were to assess cold-hardiness levels and injury of annual bluegrass [Poa annua f. eroy, 1975;Beard, 1964a). reptans (Hausskn.) T. Koyama] and creeping bentgrass (Agrostis Freyman and Brink (1967) in their study on ice cover stolonifera L. cv. Penncross) under ice cover maintained for various in alfalfa concluded that CO 2 accumulation was the periods of time under laboratory and field conditions. In the lab, prime factor in the death of herbaceous plants under cold-hardened plants of both species were subjected to either snowice sheets. In turfgrasses, Beard (1964a) suggested that covered, ice-covered, or ice-encased treatments and tested for coldcombinations of freezing and thawing in association with hardiness levels at various periods of time. Ice-encased annual bluegrass high plant tissue moisture levels might be of greater plants stored for 90 d were dead, while ice-covered and snow-covered significance than direct oxygen suffocation or toxic accuplants had cold-hardiness levels of Ϫ4؇C and Ϫ18؇C, respectively. In mulations. Rochette et al. (2000) attributed the cause contrast, at 150 days after treatment (DAT), creeping bentgrass that of ice injury on putting greens to the development of was ice encased had a cold-hardiness level of Ϫ18؇C, while snowcovered plants had a cold-hardiness level of Ϫ27؇C. In the field, bluegrass (biotype MN 42 provided by the University of Min-2004. *Corresponding author (jross@oldscollege.ca).nesota) and Penncross creeping bentgrass plants were allowed

Changes in cold hardiness levels of annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds.) were monitored under field conditions during the dehardening period of late winter and early spring. During the course of two spring periods the cold hardiness levels of the two species were monitored in conjunction with the following hydration treatments: snow cover maintained to prolong dormancy, snow removal in March, and hydration of crown tissues in combination with snow removal. Cold hardiness levels, percent crown moisture, and soil temperatures were monitored throughout this period. Cold hardiness levels were significantly influenced by year, species, hydration treatment, and a number of interactions of these factors. Generally, plants dehardened 2 wk earlier in 1997 than in 1996. On 1 April, creeping bentgrass had cold hardiness levels averaging −20°C compared to −13°C for annual bluegrass. By 15 April, creeping bentgrass plants had lost their cold hardiness advantage. Increased soil temperature was the greatest contributor to the loss of hardiness in the spring. An increase in crown moisture of 4% for annual bluegrass and 6% for creeping bentgrass occurred during the period from 25 March to 22 April. Maintaining a snow cover on plots delayed the loss of cold hardiness by 6 to 9 d in 1996 but had no effect in 1997. Maintaining a snow cover also delayed the increase in crown hydration by a week. Plants were able to partially regain cold hardiness when soil temperatures dropped.

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Spray droplet size has long been recognized as the most important variable that aerial applicators can influence to mitigate spray drift from the application site. There are several different technologies that are used by researchers to measure droplet size from spray nozzles. The objective of these studies was to determine the influence of eight spray adjuvants on the droplet size spectrum produced by two nozzles in a high-speed wind tunnel when characterized using three different droplet size measurement systems. The adjuvant, nozzles, and airspeeds used in these studies are commonly used by aerial applicators. Three droplet sizing systems (Malvern laser diffraction, PMS optical array probe, and LaVision laser imaging) were simultaneously operated to measure the spray droplet size spectra for each adjuvant, airspeed, and nozzle combination. Two spray nozzles (a D6-46 nozzle and a D2 straight stream nozzle) were evaluated in a high-speed wind tunnel at airspeeds of 45 and 58 m/sec. There were significant differences in the droplet size spectra produced by the eight spray adjuvants tested. There were also significant differences between the droplet size values reported by the three measurement systems (Malvern, LaVision, and PMS) evaluated; however, there was considerable agreement trendwise. In general, the Malvern reported smaller spray droplet size spectra values than the LaVision, while the PMS system generally reported the largest spray droplet size spectra values. These tests are the first reported studies where all three droplet sizing systems were operated simultaneously.