Evaluating Selected Fungicide Effects On Growth of Water-Stressed Impatiens walleriana

Two independent experiments were conducted to determine if applications of Pageant^® (pyraclostrobin + boscalid) or Regalia^®SC (extract of Reynoutria sachalinensis) enhanced growth in water-stressed impatiens.  Pageant and Regalia SC were applied weekly as foliar sprays to evaluate their effect on Impatiens walleriana Super Elfin XP White growth under water-stressed conditions.  In Experiment 1, four rates of each fungicide were applied based on the recommended label rate: Pageant 0, 0.5x (0.114 g·L^-1), 1.0x (0.228 g·L^-1), and 1.5x (0.342 g·L^-1); Regalia SC 0, 0.5x (18.927 mL·gal^-1), 1.0x (37.854 mL·gal^-1), and 1.5x (56.781 ml·gal^-1).   To evaluate plants under water-stress, three moisture levels were maintained based on substrate volumetric water content: 85% (well-watered), 55%, or 25% moisture.  Volumetric water content was determined by creating a soil moisture curve based on the relationship between the soil moisture readings and actual volumetric water content.  Experiment 2 was similar to experiment 1 except the three moisture treatments were based on 0, 3 or 6 days between watering.  On days of watering, water applied was determined by 85 % VWC.  In both experiments, substrate VWC, shoot and root dry weights and growth indices were measured.  Additionally, leaf samples were taken at the end of each study and immediately dipped in liquid nitrogen then placed in a negative 80°C freezer for enzyme analysis.  Results from Experiment 1, indicated a moisture × rate interaction in the 85% VMC treatment after weekly applications of Pageant.  Shoot dry weights were greater with application of 1.0x Pageant compared to all other treatments.  No moisture × rate interactions were observed for Regalia SC.  Experiment 2 showed no moisture × rate effects regardless of fungicide.  Based on these results, Pageant has the potential to enhance shoot growth when applied to well-watered but not water-stressed impatiens.