SPECIAL TOPICS: CITRUS

SOME CITRUS FACTS

Oranges


Florida produces 76% of the oranges grown in the U.S. and 20% of the world crop.
Approximately 20,358,000,000 pounds of oranges, valued in excess of $876 million, were produced during the 1996-  97 crop year on 656,600 acres.
Costs to deliver a crop to market vary with production region, market destination, and other factors. Costs for Valencia oranges grown for the processed juice market historically are approximately $2,200 per acre in the central Florida production region.
Approximately 90-95% of the Florida orange crop is processed for juice.

Grapefruit


Florida produces more than 81% of the U.S. crop and 54% of the world crop.
Approximately 5,022,000,000 pounds of grapefruit, valued in excess of $68 million, were produced during the 1996-97 crop year on 144,400 acres.
Like oranges, costs to deliver a crop to market vary with production region, market destination, and other factors. Costs for fresh packed Indian River white grapefruit historically are approximately $2,650 per acre.
More than 40% of the grapefruit grown was shipped fresh in 1992-93.

The acreage devoted to citrus production is not distributed uniformly throughout the state. Citrus acreage is decreasing on the central Florida ridge due to industrial and residential development. The center of the industry has moved south. While acreage has decreased, the total number of trees and boxes produced is increasing. Many of the pest problems, however, have remained the same.

Rind color and quality are crucial only to the fresh fruit market. Such fruit, destined for packinghouses following harvest, must have cosmetic appeal to consumers even though apparent imperfections in the outer rind usually do not adversely affect the internal quality of the fruit.

Greater pest management inputs are required for fresh fruit production. Approximately 90-95% of oranges are processed, and 55% of grapefruit is processed.

 

For more information go to: http://edis.ifas.ufl.edu/PI036
Florida Crop/Pest Management Profiles: Citrus (Oranges/Grapefruit). Michael J. Aerts & O. Norman Nesheim. Pesticide Information Office, Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. For additional Information, contact the Pesticide Information Office, University of Florida, P. O. Box 110710, Gainesville, Fl 32611-0710, (352) 392-4721. Published as CIR 1241: February, 1999. Revised: October, 2000.

CITRUS – NEMOTODES MANAGMENT

In Florida, the primary nematode species of major economic importance include
• Citrus nematode (causal agent of "slow decline" of citrus).
• Burrowing nematode (causal agent of "spreading decline" of citrus).
• Sting nematode.
• Lesion nematode.
 
Nematodes that are known pathogens of citrus seldom kill the tree, but can significantly reduce tree growth and grove productivity. Symptoms increase with time and are more apparent during periods of environmental stress or when combined with other damaging soil pests such as root weevils and Phytophthora.

Non-Chemical Control

• Preventive measures are the most effective and economic means.
• Site certification is a reliable method for production of nematode-free citrus nursery trees.
• Certified trees also reduce damage to young trees planted into old, previously infested groves.
• Cleaning equipment.
• Constructing buffer zones between infested and noninfested blocks of land.
• Proper grove management.

There is no value to managing nematodes if other problems such as poor soil drainage, insufficient irrigation, foot rot and feeder root rot, root weevils, improper fertilization, and poor disease control limit root function and/or reduce tree quality.

Chemical Control

• Has been difficult to achieve.
• Often require a period of one to two years of repeated treatment for growth improvement and significant yield returns.
• Bulldoze and burned.
• Uproot undesirable trees and delay citrus tree replanting.
• Aldicarb - (Temik) is discussed in the Pest Chemical Control section.
• Fenamiphos - (Nemacur) label permits use in of 25 of Florida's 65 counties.
• 1,3-dichloropropene - (Telone) - September 1994, the manufacture of 1,3-dichloropropene had voluntarily withdrawn for sale all Telone products in south peninsular Florida.
• Methyl Bromide - Methyl bromide as a primary treatment for control of root suckering around citrus stumps that have been removed from the grove via a tree shearing operation.
For more information go to: http://edis.ifas.ufl.edu/PI036

Florida Crop/Pest Management Profiles: Citrus (Oranges/Grapefruit). Michael J. Aerts & O. Norman Nesheim. Pesticide Information Office, Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. For additional Information, contact the Pesticide Information Office, University of Florida, P. O. Box 110710, Gainesville, Fl 32611-0710, (352) 392-4721. Published as CIR 1241: February, 1999. Revised: October, 2000

CITRUS – WEED MANAGEMENT

In the Florida citrus production system's weed management program, total acreage treated with herbicides often account for 20-25% of total production costs. Lost revenues because of poor weed control result from reduced efficiency of production and harvesting operations, direct competitive effects of the weeds, and other impacts less readily documented. Proper weed management programs positively manipulate grove temperatures during freeze events, and minimize the fire hazard during the dry winter and spring periods.

Non-Chemical Control

The choice of which combination to use depends on grove location, planting system, tree row vs. tree middle, vegetation species and cost constraints. Cultural methods include:

• Exclusion/Sanitation practices minimize species introduction, establishment and spread.
• Modification of practices that promote establishing and spreading undesirable vegetation.
• Early shading of grove floor surface by tree canopy.
• Leguminous cover crops that can supply nitrogen and require less annual maintenance.
• Infrequent cultivation provides temporary control, it also spreads and invigorates perennial weeds by increasing the number of buried seeds and distributing rhizome and stolon cuttings, tubers, and bulbs.
• Constant cultivation results in the destruction of citrus fibrous roots that normally would grow in the undisturbed portion of the soil.
• Mowing is practiced between the tree rows, but mowing has a high energy demand and high equipment costs.. Needs to be performed before seedheads form.

Chemical Control


• Glyphosate - (Roundup) - Non-selective herbicide. Used to manage weeds within the drip line under the trees, and within the row middles as a chemical mowing agent. It is selectively applied within row middles, and as a spot treatment.
• Diuron - (Karmex) Pre-emergent herbicide used for annual broadleaf and annual grass management. It is not applied to row middles
• Bromacil - (Hyvar) Pre-emergent/limited post-emergent herbicide used to manage annual broadleaf, and annual and perennial grass weeds. It cannot be used on Florida's sandy ridge-type soils.
• Simazine - (Princep) Pre-emergent herbicide used to manage broadleaf weeds, annual vines, and annual grasses.
• Norflurazon - (Solicam) Pre-emergent herbicide used to manage annual broadleaf, and annual and perennial grasses.
• Paraquat - (Gramoxone) Non-selective herbicide. Destroys all green tissue contacted.
• Oryzalin - (Surflan) Pre-emergent herbicide used to manage annual grasses and certain broadleaf weeds.

 
For more information go to: http://edis.ifas.ufl.edu/PI036
Florida Crop/Pest Management Profiles: Citrus (Oranges/Grapefruit). Michael J. Aerts & O. Norman Nesheim. Pesticide Information Office, Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. For additional Information, contact the Pesticide Information Office, University of Florida, P. O. Box 110710, Gainesville, Fl 32611-0710, (352) 392-4721. Published as CIR 1241: February, 1999. Revised: October, 2000.

CITRUS DISEASE MANAGEMENT

Non-Chemical Control

• Planting stock certified to be free of viral disease
• Planting disease resistant/tolerant varieties
• Selecting favorable grove locations not previously planted with citrus
• Planting trees with the bud union well above the soil line
• Maintaining proper placement of herbicide strips
• Skirting of trees to reduce inoculum on the ground from contacting the canopy
• Reducing or eliminating overhead irrigation
• Proper drainage and irrigation management

Chemical Control

Fungicides used to manage disease on Florida citrus is primarily limited to:

• Coppers - used to manage various citrus diseases including brown rot, melanose, citrus scab, Alternaria brown spot, and greasy spot
• Benomy - is applied to citrus trees to manage diseases such as citrus scab, green mold fruit rot, blue mold fruit rot, stem-end rot, post bloom fruit drop, and greasy spot.
• Ffosetyl-al - is applied in citrus groves to manage diseases such as Phytophthora foot rot, Phytophthora root rot, brown rot, and Phytophthora gummosis.
• Metalaxyl - is applied in citrus groves to manage Phytophthora foot rot and Phytophthora root rot.
• Oil.
Fungicides are primarily applied by ground application equipment, although certain producers occasionally might apply aerial or under tree chemigation applications.

For more information go to: http://edis.ifas.ufl.edu/PI036
Florida Crop/Pest Management Profiles: Citrus (Oranges/Grapefruit). Michael J. Aerts & O. Norman Nesheim. Pesticide Information Office, Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. For additional Information, contact the Pesticide Information Office, University of Florida, P. O. Box 110710, Gainesville, Fl 32611-0710, (352) 392-4721. Published as CIR 1241: February, 1999. Revised: October, 2000.

CITRUS PEST MANAGEMENT

The principal, non-chemical control measures used to manage insect and mite pests in Florida citrus include:
• Pest population monitoring
• Promoting the action of native and introduced exotic natural enemies
• Modifying horticultural management practices (such as irrigation, drainage and fertilizer inputs).
• Scouting groves looking for signs of pest activity
• Not using trunk wraps
• Removing and destroying infested trees
• Planting resistant rootstocks or certified pest-free trees in clean sites
• Cleaning equipment
• Constructing buffer zones between infested and non infested blocks.

Commonly used insecticides on Florida citrus include ethion, aldicarb, abamectin, chlorpyrifos, fenbutatin-oxide, sulfur, and various petroleum distillates. These products are applied as a spray to the above-ground portions of the tree. Citrus insecticides are applied either aerially or via ground application Utilizing insecticides/miticides that have different modes of action is important to Florida's citrus pest resistance management programs.

Chlorpyrifos - (Lorsban) is used as an alternative organophosphate in managing scale and thrips, and used to manage nuisance pests such as fire ants and termites in the grove.

Aldicarb - (Temik) is a granular carbamate insecticide applied to the soil to manage citrus rust mites, whiteflies, nematodes, and aphids. It has numerous use restrictions, and is strictly soil applied. The state of Florida has statewide stewardship program rules in place, and on the Florida ridge there are mandatory best management plans.

Fenbutatin-oxide - (Vendex) is an organotin miticide that has proven to be an excellent citrus miticide. Chemically unique, has broad spectrum miticide activity, and is soft on beneficials. Mixing fenbutatin-oxide with oil or copper, results in reduced residual activity. Fenbutatin-oxide has a pre-harvest interval of seven days on citrus.

Abamectin - (Agri-Mek) is a soil bacterium to manage mites and the citrus leafminer. Abamectin cannot be applied via aircraft.

Oil - is applied to help suppress citrus rust mites, spider mites, scale, and whiteflies respectively. It exhibits certain fungicidal properties and is used to manage greasy spot.

Sulfur - is used to help suppress populations of citrus rust mites. Sulfur may be legally applied on citrus up to and including the day of harvest but the restricted entry interval under the Worker Protection Standard for sulfur is 24 hours. Sulfur cannot be combined with oil, or applied within three weeks of any oil spray, as fruit burn will result. Sulfur is the most persistent pesticide currently used on Florida citrus. Multiple sulfur uses are disruptive to the established Integrated Pest Management program for mites.

 
For more information go to: http://edis.ifas.ufl.edu/PI036
Florida Crop/Pest Management Profiles: Citrus (Oranges/Grapefruit). Michael J. Aerts & O. Norman Nesheim. Pesticide Information Office, Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. For additional Information, contact the Pesticide Information Office, University of Florida, P. O. Box 110710, Gainesville, Fl 32611-0710, (352) 392-4721. Published as CIR 1241: February, 1999. Revised: October, 2000.