Weed Management in FL Sugarcane Curtis Rainbolt Everglades REC, Belle Glade, FL

Outline General sugarcane information Sugarcane production –Planting –Harvest Weed management –Factors that influence management –Chemical –Mechanical –Cultural

FL Sugar Approximately 400,000 acres of sugarcane Grown by FL Crystals, US Sugar, and Sugar Cane Growers Cooperative of FL

Sugarcane Biology Sugarcane is a giant perennial grass (Poaceae) Tribe: Adropogoneae Commercial clones are typically hybrids of Saccharum officinarum L. and a combination of S. barberi, S. robustum, S. sinese, and spontaneum

Growing Season Planted September to December Grows for approximately one year between harvests Harvest season runs from October through March Cane that will be replanted (successively) is harvested first

Sugarcane Growth Grows rapidly in the summer period of warm temperatures and high rainfall Matures, ripens, and is easily harvested during the cool, dry winters The lake provides a winter warming effect

Soils About 90% is grown on muck soilsAbout 90% is grown on muck soils ~ 70 to 90% organic matter and do not require N fertilizer~ 70 to 90% organic matter and do not require N fertilizer Remainder is grown on sand soils (1-3% OM)Remainder is grown on sand soils (1-3% OM)

Planting Propagated with vegetative cuttings Planted by both hand and machine 5 ft row spacing

Sugarcane Harvest Most sugarcane in FL is burned prior to harvest to remove leaf material Yields range from 20 to over 100 tons/acre Yields typically decrease with each ratoon crop The average is around 45 tons/acre

Green Cane Harvest As the population of S. FL grows, air quality becomes a larger issue Many sugarcane producing countries are phasing out burning The impact of GCH on the FL production system is unknown GCH results in a heavy residue layer (5-15 tons/acre)

Weed Management Overview Most growers utilize an integrated approach (primarily chemical and mechanical) Sugarcane is relatively competitive and somewhat forgiving South FL environment is ideal for many tropical and sub-tropical weed species

Factors that influence weed management Virtually a monoculture crop Row spacing Crop age Minor use crop High organic matter soils Corporate mentality (sugarcane prices) and tradition

Monoculture Crop rotation is a valuable tool for weed management The majority sugarcane is replanted every 3 years Only a small percentage of the fields are rotated to vegetables or left fallow

Row spacing Sugarcane is planted on 5 ft rows Although a competitive crop, grows slowly at temperatures below 70 F Results in bare ground following planting and harvest until ~March Cultivars vary in their canopy architecture

Crop Age Yields typically decrease each year Influences the crop value and the amount growers are willing to spend for weed control Additionally, some growers do not apply herbicides to plant cane Weed pressure typically increases

Minor use crop Although a major crop in south Florida, sugarcane is a minor use crop in the US and worldwide Consequently, there are a limited number of registered herbicides Little incentive for new product research in current ag chemical industry climate

Muck Soils High organic matter (70-90%) has considerable effect on duration of weed control with PRE herbicides Despite high use rates, control can last less than 4-6 weeks High rates increase likelihood of crop injury Results in a reluctance to use PRE herbicides

Corporate Mentality and Tradition Weed control decisions are often made by accountants Results in a fixed budget and plan for weed control Goal is often quantity of acres treated rather than quality Traditional reliance and overuse of on tillage

Application timing Envoke + Asulox applied to 4-5 inch tall crabgrass and fall panicum applied 13 days laterapplied 20 days later

Chemical Weed Control Both PRE and POST herbicides are used PRE treatments are typically POST to the crop Most herbicide applications are banded over the row Mainly older chemistries Short residual with PRE herbicides

PRE herbicides Atrazine is the backbone of most weed control programs –Used both PRE and POST –Applied at 3-4 lbs per acre, and 1 to 2 times per season –Typically last 3-5 weeks Heavy reliance on triazine herbicides

POST Herbicides Asulam is used extensively for grass weed control Because of cost it is often applied late to insure only 1 application before canopy closure Trifloxysulfuron, halosulfuron for nutsedge control 2,4-D for broadleaf weed control

Mechanical Weed Control Varies depending on plant cane or ratoon cane Plant cane-scratchers are used over the top of the cane and tines are removed as the can gets larger Ratoon cane-disk cultivators are used for weed control in row middles

Cultural Weed Control Selection of cultivars that have quick canopy closure Seed cane from clean fields Control of weeds on field borders and ditch banks