|Richard Jr, Edward|
Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 12, 2006
Publication Date: March 18, 2006
Citation: Richard Jr, E.P., Dalley, C.D. 2006. Sugarcane (saccharum spp.) response to flumioxazin. Weed Technology. 20:238-244. Interpretive Summary: The number of herbicides registered for use in sugarcane is limited and the majority has a similar mode of action by disrupting the plant’s ability to convert sunlight into food for growth. The registration of flumioxazin for use in sugarcane provides growers with a herbicide that has an alternative mode of action for broadleaf weed control that may prove useful in programs aimed at preventing the development of herbicide resistant weeds. Experiments were conducted to evaluate sugarcane varietal tolerance to flumioxazin applied at various timings in plant cane (first production year) and first ratoon (second production year) crops. Visual injury symptoms, observed only after postemergence applications of flumioxazin in both the plant and ratoon crops, consisted of reddening and necrosis of treated leaves and stunted growth. In plant-cane, stalk height was reduced when flumioxazin was applied over the top of the crop’s foliage (postemergence) in both the fall and spring. Early spring postemergence applications reduced the number of harvestable stalks of the varieties HoCP 91-555, and LCP 85-845, but not LCP 85-384; and yield losses occurred when flumioxazin was applied postemergence in the spring regardless of timing, but not when applied at planting prior to crop emergence (preemergence). In first ratoon sugarcane, stalk numbers and heights were reduced following sequential late spring overtop followed by a directed (under the crop canopy) postemergence flumioxazin application following the last cultivation regardless of variety. Yield losses occurred with all overtop postemergence applications of flumioxazin, but not with the post-directed applications following the layby cultivation. It appears that flumioxazin is relatively safe to sugarcane when applied after planting but before crop emergence, late-winter when the crop is beginning to recover from winter dormancy, and as a post-directed spray at layby. The latter application would give growers another option for controlling late-emerging weeds such as morningglories in sugarcane. Use of this herbicide, with its alternative mode of action, could also help to slow the development of herbicide resistant weeds.
Technical Abstract: Experiments were conducted to determine response of the sugarcane cultivars HoCP 91-555, LCP 85-845, and LCP 85-384 to flumioxazin during the first (plant cane) and second (first ratoon) production years. In the plant cane crop, flumioxazin was applied in September or October [at planting preemergence (PRE)], in late October or mid-November [fall postemergence (FPOST)], in mid-to late March [early spring postemergence (ESPOST)], and in mid-May as a post-directed spray (PDS) following layby cultivation, along with sequential applications of FPOST followed by ESPOST. During the first ratoon crop, flumioxazin was applied in mid to late March (ESPOST), in late April [late-spring (LSPOST)], and in mid-May as a PDS following layby cultivation, along with sequential applications at LSPOST followed by PDS. Flumioxazin injury to sugarcane consisted mainly of stunted growth and reddening and necrosis of treated leaves. In plant cane, injury was 28% 2 weeks after treatment (WAT) when applied ESPOST in one experiment but less than 10% in the other, and was no more than 13% in either experiment at 6 WAT. In the first ratoon crop, injury was around 15% when applied ESPOST in the first experiment, but no injury was observed 6 WAT. However, in the first ratoon, injury to all cultivars was 25-30% when applied LSPOST. When applied as a PDS, injury was no more than 15% 4 WAT. Stalk height was reduced when flumioxazin was applied as a sequential application (FPOST followed by ESPOST) in plant cane (15 cm compared with nontreated) and LSPOST followed by PDS at layby in first ratoon sugarcane (23 to 28 cm compared with nontreated). In plant-cane ESPOST applications of flumioxazin reduced sugar yield (9-28%) within all three cultivars used in this study in both experiments with only one exception. Sequential (FPOST followed by ESPOST) applications reduced sugar yield within all cultivars (6 to 37%). PDS applications at layby reduced yields (7-12%) in the first experiment, but not in the second experiment. In the first-ratoon crop, LSPOST applications of flumioxazin reduced sugar yield (7-11%), sequential flumioxazin applications (LSPOST followed by PDS) reduced sugar yields (8-19%), and PDS applications at layby did not reduced yield. It appears that there is little if any difference in tolerance to flumioxazin for the cultivars used in this experiment. To avoid risk of yield loss, flumioxazin should not be applied as an over-top POST treatment to weeds in actively growing sugarcane, and care should be taken to minimize spray contact with sugarcane leaves when applying flumioxazin as a PDS at layby.