Efficay and Phtotoxicity Evaluations of Marengo G and BroadStar G

Marengo G (indaziflam, OHP, Inc.) is a new product for the nursery industry that contains 0.0224% indaziflam.  The objectives of this study were to determine the phytotoxicity of four rates of Marengo G on seven species at two locations, the efficacy on three weed species at one location and compare to an industry standard granular, BroadStar (flumioxazin, Valent U.S.A) and untreated controls.  Two cooperating nurseries were selected for the phytotoxicity evaluations of Marengo G; Studebaker Nursery (New Carlisle, OH) and Willoway Nurseries (Huron, OH).  Species selected at Studebaker included Viburnum x’Juddi’, Hydrangea paniculata ‘Little Lamb’, and Hemerocallis ‘Stella d’oro’.  Species selected at Willoway included Rhododendron ‘Nova Zembla’, Pieris ‘Red Mill’, Azalea ‘Karen, Ilex xmeservea ‘Blue maid’, Hydrangea paniculata ‘Limelight’ and Viburnum x’Juddi’.  Treatments were applied on May 1, 2013 and reapplied on June 26, 2013 at Willoway and May 6, 2013 and reapplied on June 17 at Studebaker.  Evaluations consisted of visual ratings (0-10) with <3 being commercially acceptable for phytotoxicity and >7 being commercially acceptable for efficacy.   A completely randomized design was used with each treatment having four replications and three subsamples/replication.  At Willoway, Ilex xmeservea was the only species that showed a significant difference from the control with Marengo G.  At Studebaker, all three species tested showed some susceptibility from the Marengo G.  Unlike at Willoway, Viburnum with Marengo G at 150, 200 and 400 lb/ac showed leaf distortion and progressive injury over time.  At Studebaker, Marengo G at 400 lb/ac and the BroadStar provided ratings that were above commercially acceptable at 1 WA2T on the Viburnum.  Hydrangea was significantly injured from all treatments.  Injury from the 400 lb/ac rate was the most severe.  The injury from the 400 lb/ac rate was not statistically different than the BroadStar injury at 150 lb/ac.  Data from this trial supported previous research indicating Hydrangea is very susceptible to indaziflam, showing stunting, whitening, and brittle stems.  Hemerocallis injury from the Marengo G was less severe and persistent than from BroadStar, conjuring with previous OSU studies that Hemerocallis shows stunting only initially from Marengo G.  Marengo and BroadStar controlled bittercress and crabgrass very well.  At 4 WAT, all treatments provided significantly lower counts for woodsorrel than the untreated control.  By 8 WAT, residual control had decreased for all treatments.  the Marengo G rate of 200 lb/ac should be reapplied at 8 WAT for commercially acceptable weed control through the season.