The 2011 ASHS Annual Conference

Liverwort control is a concern for many nursery growers, especially during propagation in the Midwest U.S.A, and the need for liverwort control has been expressed with many Michigan nurserymen, and liverwort control is also one of the main focuses of the IR-4 program for ornamentals.  Three cooperating nurseries were selected as sites to test the liverwort protocol, which were Lincoln Nurseries (Grand Rapids, MI), Zelenka Nursery (Grand Haven, MI), and Spring Meadow Nursery, Inc. (Grand Haven, MI).  Species selected for phytotoxicity ratings at Lincoln Nurseries included Buxus x ‘Green Velvet’, Berberis thunbergii ‘Crimson Pygmy’, Ilex x merservea ‘China Girl’, and Thuja occidentalis ‘Nigra’.  Species selected for phytotoxicity at Zelenka Nursery included Euonymus x ‘White Album’, Juniperus horizontalis ‘Hughes Gold’, Chaenomeles x‘ Double Take Pink Storm’, and Viburnum dentatum ‘Double take’.  Species selected for phytotoxicity at Spring Meadow Nursery included Syringa meyeri ‘Paliban’ and Hydrangea amorences ‘Invincibelle’.  Phytotoxicity and efficacy visual ratings were taken at one, two, and four weeks after the first treatment (WA1T) and one, two and four weeks after the second treatment (WA2T).  Liverwort control treatments consisted of Bryophyter™ at 1% v/v, Champ DP™ at 5.5 lb/100 gal, Racer™ at 0.2% v/v, Scythe™ at 10% v/v, flumioxazin (SureGuard, Valent U.S.A.) at 12 oz/ac + nonionic surfactant at 0.25% v/v, dimethenamid-p (Tower, BASF Corp.) at 32 oz/ac, TerraCyte Pro™ at 0.5 lb/gal, and WeedPharm™ at 10% v/v.  Scythe and SureGuard were the most phytotoxic, yet most efficacious treatments of the study.  SureGuard injured Hydrangea, Buxus, Berberis, Ilex, and Euonymus.  Scythe was injurious to all species tested.  From these trials, it can be concluded to use Scythe only as spot treatments or as a direct spray, which is indicated on the label.  The other treatments were not consistent with the amount of control; i.e. there was some control in some of the pots, but liverwort in other pots was totally unaffected.  Increasing the rates of those treatments could provide some additional control.  From these trials, SureGuard could be used over the top of Thuja, viburnum, and Juniperus, and possibly Syringa.