Efficacy of subsurface and foliar penoxsulam and fluridone applications on giant salvinia

摘要

Giant salvinia (Salvinia molesta Mitchell) continues to be problematic and spread throughout the southern portion of the United States. Traditional management of this invasive weed has been application of the foliar herbicides diquat, glyphosate, andcombinations of the two. Unfortunately, thick surface mats that limit contact with foliar sprays and fast recovery potential have resulted in mixed efficacy. Three experiments were conducted to determine the efficacy of subsurface and foliar penoxsulam and subsurface fluridone applications on giant salvinia. These studies were conducted to determine concentration exposure time (CET) relationships, determine if repeat applications can be as effective as single static applications of each respective herbicide, and if subsurface or foliar applications will control mature giant salvinia compared to standard foliar treatments used operationally. In the CET experiment, both herbicides were more effective at growth regulating or controlling giant salvinia when exposed >8 wk, regardless of concentration. All penoxsulam concentrations evaluated (5 to 40 mu g a.i. L~(-1)) resulted in initial growth regulation of giant salvinia as early as 1 week after treatment, followed by either new healthy growth (1 to 4 wkexposure) or tissue destruction (>4 wk exposure). Static penoxsulam treatments (10 and 20 pg L~(-1)) decreased plant dry weight 88 to 100% compared to the nontreated control. Penoxsulam foliar (24 h exposure) plus fluridone subsurface, penoxsulam foliar(24 h exposure), and penoxsulam foliar (static) reduced plant biomass to below pretreatment level in the third experiment. All herbicide treatments, except fluridone subsurface (20 jig a.i. L1 with 8 wk exposure), were as effective or provided greater giant salvinia control than the standard operational mix of glyphosate plus diquat plus two surfactants. These data confirm that penoxsulam and fluridone can be used operationally to control giant salvinia.