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