Weed Management in FL Sugarcane

Curtis RainboltEverglades 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 About 90% is grown on muck soils on muck soils

• ~ 70 to 90% ~ 70 to 90% organic matter and organic matter and do not require N do not require N fertilizerfertilizer

• Remainder is grown Remainder is grown on sand soils (1-3% on sand soils (1-3% OM)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 later applied 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