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Overview of Citrus Grower Nutritional Spray Compositions
Tim SpannInternational Citrus and Beverage Conference
Clearwater Beach, FL
16 September 2011
Huanglongbing (Citrus Greening)
• Discovered near Homestead in Aug. 2005
• Presumed caused by a fastidious phloem-limited bacteria – Candidatus Liberibacter asiaticus
• Spread by the Asian citrus psyllid
– Discovered in Florida in 1998
Aug. 2005 June 2006 Oct. 2007
The End of Citrus
Feb. 2006 Apr. 2011
Where It All Began
• In 2006 Maury Boyd chose not to remove HLB-infected trees and treat the disease symptoms
• Targeted the known and the unknowns
• Single handedly created a revolution within the Florida citrus industry
The “Maury Boyd Cocktail”
The knowns
• Epsom salts (MgSO4)
• Tecmangam (MnSO4)
• ZnSO4
• NaMoO4
• 13-0-44
• K-phite– Phosphorous acid – systemic
fungicide/bactericide
• 435 oil
The unknowns
• SAver– 2-0-10 (Salicylic acid?)
• Serenade Max– Biofungicide (Bacillus subtilis
strain QST 713)
• OxiDate– Broad spectrum
bactericide/fungicide (H2O2)
Beyond the Maury Boyd Cocktail
• Every fertilizer manufacturer now produces their own program of foliar nutrition for HLB
Labeling requirements and product quality
Regulation of Fertilizers
• EPA does not regulate fertilizers from a safety or quality perspective, only pesticides (includes fungicides, bactericides, miticides, etc.)
• EPA does regulate pollution resulting from fertilizer use
• Individual states regulate the quality of fertilizers, consumer protection and labeling
Regulation of Fertilizers
• Association of American Plant Food Control Officials (AAPFCO) is an organization of fertilizer control officials from each state
• Strives for uniformity of regulations by consensus among each state
Florida Fertilizer Rules
• “Fertilizer” means any substance which:– Contains one or more recognized plant nutrients
and promotes plant growth
– Controls soil acidity or alkalinity
– Provides other soil enrichment
– Provides other corrective measures to the soil
• “Guaranteed analysis” means the percentage of nutrients or measures of neutralizing capability claimed to be present in a fertilizer
Adulteration Levels for Metals in FertilizersFertilizers that contain guaranteed amounts of phosphates and/or micronutrients are adulterated when they contain metals in amounts greater than the levels of metals established by the following:
Metals ppm per 1% P2O5 ppm per 1% micronutrients
Arsenic 13 112
Cadmium 10 83
Cobalt* 3,100 23,000*
Lead 61 463
Mercury 1 6
Molybdenum* 42 300*
Nickel 250 1,900
Selenium* 26 180*
Zinc* 420 2,900*
What are all of these products and what’s in them?
First Things First
• Foliar applied nutrient formulations are very different from ground applied nutrient formulations
– Very pure, high grade chemicals
– Water soluble powders or liquid formulations
The Laundry List
• Macronutrients
– N, P, K
• Secondary and Micronutrients
– Various chelated products
– MgSO4
– MnSO4
– ZnSO4
– NaMoO4
• Phosphites (PO33-)
– Salts of phosphorous acid
– Fungicide/bactericide?
• SAR inducers
– Salicylic acid
• Biofungicides
– Bacillus subtilis strains
– SAR inducers?
Macronutrients
• Liquid formulations generally derived from:
– Urea, Ammonium Nitrate, Nitrates [KNO3, Mg(NO3)2]
– Phosphorous acid, Dipotassium phosphate, Ammonium phosphite
– Potassium hydroxide
• For HLB, purchasing dry soluble macronutrients is uncommon, although “spray grade” urea is a common additive to enhance uptake of other agrochemicals
Secondary and Micronutrients
• Liquid formulations generally derived from:
– Sulfates (Fe, Mg, Mn, Zn)
– Sodium salts (B, Mo)
– Chelates – most commonly EDTA, but also glucoheptonate, humic acid, amino acids, citric acid
• Dry soluble micronutrients are usually in the form of sulfates
Label Examples
Non-plant Food Ingredients
• Currently an approved term in California and Oregon– Proposed to be struck and use only the terms
“beneficial substance” and “beneficial compounds” (AAPFCO, July 2007)
– Approved as tentative (Feb. 2009)
• No reference to non-plant food ingredients, or beneficial substances or compounds in the Florida Fertilizer Registration and Labeling Guidelines
Phosphites
• Often advertised and sold as fertilizers, but are not
– Phosphite is converted to phosphate too slowly to be of much use as a phosphorous source
• They do control certain fungus-like pathogens of the order Oomycota (Phytophthora and Pythium)
– e.g., Aliette (Bayer) – Al phosphite
Phosphites Used in Citrus
• “TKO” Phosphite 0-29-26 – GP Solutions
• Nutri-Phite 2-40-16 – Biagro
• K-phite 7LP – Plant Food Systems
• AG-phite 57 – Plant Food Systems
SAR-inducers
• Systemic Acquired Resistance – a whole-plant response that occurs after a localized exposure to a pathogen– Associated with the induction of a family of genes
known as “pathogenesis-related” or PR genes– Requires the accumulation of endogenous salicylic
acid (SA)– Can be induced in some species by the exogenous
application of SA or SA analogues (acibenzolar-S-methyl – Actigard)
• Has not been consistently shown to be effective against systemic bacterial diseases
Salicylic Acid
• Two products available for use in citrus that contain SA from G.P. Solutions
– Tiger SA • 10% solution of SA
– Recover RX 3-18-18• 0.5% SA
• Labeled as a non-plant food ingredient
Other Non-plant Food Ingredients
• Humic Acid – derived from humus (decayed organic matter) through alkaline and acid extractions
– Not well defined, no single compound
• Purported to directly or indirectly enhance plant growth
• Alpha-Keto Acids (e.g., pyruvic acid)
– Purported to invigorate plants, improve yields and enhance nutrient uptake
– May be derived from amino acids (exact processes are patented)
Summary
• The majority of products being used are standard plant nutrients – They were used before HLB, but are no doubt
being used much more now
• All products are labeled and comply with state regulations for fertilizers– Intent vs. spirit of the regulations?
• Regulations do not restrict fertilizer use except voluntarily through BMPs
Summary
• Pesticide use has also increased considerably since 2005
– Inert ingredients must be registered with EPA, but do not currently need to be disclosed on labels
• Regulations do limit annual usage of pesticides and MRLs are in place
• Grey areas exist in registration of products as fertilizers or pesticides
Thank you