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Many plants have mechanisms of physical or chemical resistance that protect them from herbivores in their environment. The ornamental plant Pachysandra terminalis Sieb. and Zucc is highly unpalatable to voles, but the nature of this resistance is not fully understood. Extracts of P. terminalis were prepared to determine the extent to which chemical constituents could account for its avoidance by voles. A bioassay in which samples were mixed with applesauce showed that ethanolic extracts were highly deterrent to captive prairie voles (Microtus ochrogaster Wagner, 1842). Bioassay-guided fractionation of ethanol extracts showed that antifeedant activity was present in both polar and non-polar fractions. Further separation of each fraction by open column chromatography and high pressure liquid chromatography revealed that combinations of compounds were responsible for the deterrent activity. Preliminary ultraviolet and mass spectroscopic analyses indicated that steroidal alkaloids that are characteristic of this plant are likely to be involved.

Equal average container temperatures during prolonged periods of low outside air temperatures were achieved by unheated structures covered with either a double-layer of clear polyethylene or a double-layer with the inner layer translucent and the exterior clear polyethylene. Single-layer structures were less effective, with clear polyethylene affording more protection than translucent. Excessively high mid-day temperatures in both the single- and double-layer clear houses increased the probability of desiccation injury and affected the quality of the nursery stock. Fluctuations of air temperatures below 0°C were most rapid in the clear houses, and appear to depend greatly on the relative humidity, which affects the thermal conductivity of the air. Container temperature fluctuations were similar whether the container soil water was frozen or unfrozen. The best covering tested thus far appears to be a double-layer with the interior translucent and the exterior clear polyethylene. This covering moderates low container temperatures, high mid-day temperatures, desiccation problems, rapid temperature fluctuations and concomitant management problems.

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