Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2006
Publication Date: 9/1/2006
Citation: Richardson, B.M., Wehtje, G.R., Gilliam, C.H., Fain, G.B. 2006. Postmergence oxalis control with diuron: minimizing crop injury with timely irrigation. Journal of Environmental Horticulture 24(3):129-132.
Interpretive Summary: Postemergence weed control in container grown nursery crops is becoming increasingly important to producers due largely to increasing labor costs. Oxalis or yellow wood sorrel (Oxalis stricta) is a serious problem in many regions of the United States, especially with container grown crops emerging from winter protection. Previous research has shown that diuron has the potential to control oxalis when applied postemergence over-the-top to dormant camellia (Camellia japonica ‘Pink Icicle’), liriope (Liriope muscari ‘Big Blue’) and spirea (Spiraea x bumalda ‘Anthony Waterer’). However in some cases slight crop injury resulted from the application of diuron, and injury was more severe with actively growing crops. This research indicated that irrigation at 1 hr after diuron application reduced diuron–induced injury without compromising oxalis control.
Technical Abstract: Experiments were conducted to evaluate container nursery crop tolerance and oxalis control with postemergence applied diuron as influenced by timely overhead irrigation. Intent was to identify an interval between application and irrigation that may reduce crop injury without compromising oxalis control. Diuron was applied at a common rate of 1.0 lb ai/A to oxalis and two nursery crops (Camellia sasanqua ‘Alabama Beauty’ camellia, and Rhododendron indicum ‘G.G. Gerbing’, azalea). Treatments consisted of irrigation at 1, 2, 4, 8, 12, 24, or 48 hr after application. Oxalis control was equivalent whether treated plants were irrigated within either 1 hr or 48 hr after application. Camellia exhibited no visible injury regardless of treatment. Azaleas exhibited diuron-induced injury, however injury was reduced if plants were irrigated within 1 hr of diuron application. 14C-diuron was used to determine the absorption rate of foliar-applied diuron into oxalis, camellia and azalea. Absorption by oxalis was relatively rapid, and reached a maximum (~68% of applied) within 8 hr after application. Camellia and azalea absorbed a smaller percentage of the amount applied, and absorption was more protracted over time compared to oxalis. Azalea absorbed slightly more than camellia. Diuron has potential for use as an over-the-top application for postemergence oxalis control, and timely irrigation has the potential to reduce injury to sensitive crops.