Herbicide efficacy to control Parthenium (Parthenium hysterophorus) under grove conditions in Homestead, Florida

Parthenium, hysterophorus L. is in the Asteraceae and common names include parthenium, carrot weed, ragweed parthenium, and star weed. Indigenous to Mexico and Central and South America, parthenium is considered very invasive and is a major weed pest in India, Australia, Taiwan, Ethiopia, and parts of the U.S. In the U.S., parthenium is found in 23 states, and in Florida, parthenium is found in 22 of 67 counties. Parthenium invades agricultural areas, disturbed areas, range and grasslands, and urban areas, and has become resistant to control with glyphosate. Four herbicides alone and in specific combinations [Finale (R) (glyphosinate-ammonium), Roundup-Ultra Max (R) [glyphosate N-(phosphonomethyl) glycine], Finale (R)+Roundup-Ultra Max (R), AIM (R) EC (carfentrazone-ethyl), and MM01 (proprietary)] were tested in two field trials for their efficacy in controlling parthenium under south Florida grove conditions. Treatments were laid out in a completely randomized design with three to five plots per treatment. Parthenium plants were counted within a 19-inch square grid prior and post herbicide application in each trial. Data were analyzed as repeated measures analysis. In the first trial, parthenium control was significantly greater for Finale (R) alone and Finale (R)+Roundup-Ultra Max (R) compared to water sprayed control, AIM (R) EC+crop oil, MM01+Silwet (R), and Roundup-Ultra Max (R) alone. In the second trial, control of parthenium with Finale (R) alone at the rate of 3 or 4 quarts/acre and 2 rates of Finale (R)+Roundup-Ultra Max (R) were significantly better than the water sprayed control. Finale (R) alone effectively controlled parthenium under grove conditions in south Florida.