Production Practices & HLB

Impacts on Fruit Marketability

Mark RitenourUniversity of Florida

Indian River Research and Education Center

The Importance of High Packouts

• Higher packouts = more $$ to grower

• There comes a point when economics dictate taking the

crop straight to the processor

VS

What Influences Packout?

• Age of Trees

• Climate & Weather

• Disease

• Cultural Practices

• Harvest Practices– Spot picking = lower packouts in subsequent picks

• Postharvest Handling Practices

The Importance of Satisfied Markets

• Claims or

rejected loads

at destination

markets are

EXTREMELY

COSTLY!

Three Focus Areas

• Peel Breakdown

• Fruit Decay

• Pesticide Residues

Diplodia stem-end rot

Stem-end Rind Breakdown

Possible Causes of Peel Breakdown

• Water stress?

• Nutrient

Imbalances?

• Low RH postharvest or

sudden changes in

relative humidity (“RH

shock”)?

Water Stress Results

• White grapefruit harvested 48 days after withholding water,

held for 3 d at 70F (60% RH), washed (no wax), and then held

under ambient conditions on the air-conditioned room floor

~73F.

Days after

harvest

Treatment

13 Control 91.33 az 3.33 1.33 3.33 2.67 3.33 6.00 a

Water def. 78.67 b 5.33 4.67 5.33 10.00 6.00 16.00 b

Significance

25 Control 81.00 a 4.67 1.33 5.33 3.33 a 13.00 14.33

Water def. 60.00 b 15.33 6.00 17.33 11.33 b 13.33 24.00

SignificancezValues within each column followed by unlike letters are significantly different by Duncan's multiple range test at P < 0.05.

yIrrigation and rain witheld for 49 days prior to harvest.

NS,*Nonsignificant or significant at P < 0.05, respectively.

Stem-end rind

breakdown (%)

Total peel

breakdown (%)

Marketable

(%)

Stem-end

rot (%)

Penicillium

(%)

Total decay

(%)

Peel pitting

(%)

NS *

* NS NS NS * NS NS

* NS NS NS NS

Roots & HLB

Johnson et al., 2014

weig

ht

sta

rch

weig

ht

sta

rch

weig

ht

sta

rch

Roots & HLB

Johnson et al., 2014

density

sta

rch

density

sta

rch

density

sta

rch

LAS detected

Treatments

• Control – normal grove practices

• Foliar MKP Treatments (23.5 lb MKP/acre + 4 lb/acre

low-biuret urea, 125 gal/acre)

– 8 lb K2O/acre

• Foliar Magnesium (6% Epsom salts)

• Foliar MKP + Mg

• Vapor Gard® (1% or 2%)

• WashGard (1%)

• Polymer Delivery System (1%)

Results – Foliar MKP• Star Ruby red grapefruit harvested two weeks after commercial

MKP application, held for 4 d at 73F (60% RH), washed (no wax),

and then held under ambient conditions on the air-conditioned

room floor ~73F

Harvestz

(weeks)

Days after

harvesty

Treatment

2 25 Control 70.50 ax 1.00 1.00 27.50 a 27.50 a

MKP 86.50 b 1.00 1.50 11.00 b 11.00 b

Significance

3 27 Control 82.58 10.25 1.67 7.67 a 9.33 a

MKP 85.70 9.66 0.67 2.64 b 2.97 b

Significance

4 12 Control 64.32 b 2.52 6.87 25.32 a 32.10 a

MKP 72.89 a 3.19 4.61 18.89 b 23.50 b

Significance

Marketable

(%)

NS

Total peel

breakdown (%)

** NSNS ** **

Total decay

(%)

Pitting

(%)

Stem-end rind

breakdown (%)

*

*** NS NS *** ***

NS NS *

Results - 2009

• Fruit held 2 to 4 days at 70F (60% RH), washed & waxed

(carnauba), and then held under ambient conditions on the air-

conditioned room floor ~73F

Peel Breakdown (%)

Grapefruit 1 Grapefruit 2 Valencia

Control 40.3ab 46.2 33.9a

MKP 29.1abc 28.2 22.7ab

Mg 21.6abc 27.8 19.5b

MKP + Mg 2.6c

Vapor Gard® 12.5c 17.6 10.7bc

• Postharvest peel breakdown can be promoted by tree water

stress before harvest

• Since HLB damages tree roots, it may also increase tree/fruit

water stress and peel breakdown– THIS NEEDS TO BE TESTED!

• Foliar application of K can significantly reduced peel

breakdown

– BUT NOT ALWAYS!

• Vapor Gard (1% or 2%) has performed well over several

seasons in reducing postharvest peel breakdown

Conclusion

Fruit Decay - on Tree!

• Diplodia (Lasiodiplodia theobromae)causes fruit stem-end rot and was:

– Consistently detected in the abscission zone and juice of HLB-infected fruit

– Greater abundance of Diplodia was positively correlated with lower fruit detachment force

– Fruit ethylene production is positively correlated with Diplodia infection levels

Zhao et al., 2015, 2016

Preharvest Materials Tested

• Benlate (Benomyl) – 2 lb/acre

• Topsin M (Thiophanate-methyl) – 2 lb/acre

• Topsin F (Thiophanate-methyl) – 16 oz/acre (liquid)

• Headline (Pyraclostrobin) – 16 oz/acre

• Kocide DF (Copper) – 4 lb/acre

• Abound (Azoxystrobin) – 16 oz/acre

• Enable (Fenbuconazole) – 8 oz/acre

• Aliette (Fosetyl-Al) – 5 lb/acre

Preharvest Materials Tested

• Phosphorous acid (Nutriphite or Phostrol) – 4 pints/acre

• Pristine (Pyraclostrobin + Boscalid) - 18.5 oz/acre

• Actigard (Acibenzolar-S-methyl) – 100ppm + 0.025% Silwet

• Scholar (Fludioxonil) – 8oz/acre

• Switch (cyprodinil & fludioxonil) – 14 oz./A

• Bravo (chlorothalonil) – 6 pts./A

• OxiDate or HDH Peroxy (H2O2) – 1%

• PAA (15%) – 85 ppm

Compound

Control 42.5 aw

48.2 79.9 18.8 a 21.2 a 34.1 ab 37.8 ab

Ferbam 43.7 a

Acibenzolar-S-Methyl 65.5 78.8 16.2 a 15.6 a 51.2 a 45.1 a

Fenbuconazole 51.6 a 50.6 76.2 18.7 a 24.3 a 37.0 ab 46.0 a

Fosetyl AL 59.9 a 50.2 77.6 16.4 a 14.1 ab 30.0 b 34.1 abc

Phosphorous acid 29.3 ab 44.7 84.8 20.9 a 36.4 a 51.6 a 22.0 bc

Copper hydroxide 39.6 a 48.2 78.7 13.3 a 37.9 a 40.6 ab 26.0 bc

Azoxystrobin 39.7 70.2 13.5 a 25.5 a 37.2 ab 38.0 ab

Benomyl 6.2 b 40.1 74.0 3.0 b 1.4 b 2.9 c 18.2 c

Significance * *** **

41 d 86 d 79 d

--- --- --- --- --- ---

58 dx

34 d 78 d 77 d

*v

NS NS **

---

---

23 Nov.y

20 Sept. 9 Oct. 13 Dec. 21 Dec. 19 Mar. 2 Apr.

18 Sept. 2000 11 Dec. 2000 16 Mar. 2001

'Sunburst' 'Fallglo' 'Sunburst' 'Marsh'

Percent Total Decay

4 Nov. 1999z

Compound

Control 60.0 71.8 ay

41.7 a 31.8 a 30.5 60.2 a

Pyraclostrobin 51.8 50.8 b 36.5 ab 17.7 ab 28.3 48.2 a

Phosphorous acid 46.4 45.9 b 29.1 ab 16.7 ab 29.9 47.2 a

Thiophanate methyl 45.1 47.2 b 14.1 c 6.1 b 17.2 15.0 b

Benomyl 42.4 41.3 b 22.5 bc 14.2 ab 12.3 14.0 b

Significance

25 Apr. 6 May.6 Dec.y

18 Dec. 27 Feb. 11 Mar.

NSw

* * * NS **

122 d84 d 118 d 123 d 133 d81 dx

25 Feb. 2002 23 April 20024 Dec. 2001z

'Sunburst' 'Marsh' 'Valencia'

Percent Total Decay

Summary of ExperimentsPreharvest application

Healthy fruit 1999-2005

Treatment Tangerine Orange Grapefruit

Benomyl 4z/6

y 1/2 5/6

Thiophanate-methyl (WSB) 2/3 1/2 3/5

Thiophanate-methyl (FL) 1/1

Pyraclostrobin 1/1 0/1 1/3

Phosphorus Acid 1/4 0/1 0/4

Pyraclostrobin + Boscalid 0/2

Copper hydroxide 0/3 0/1

Azoxystrobin 0/2 0/2

Fenbuconazole 0/3 0/1

Fosetyl AL 0/3 0/1

Acibenzolar-S-methyl 0/2 0/1zNumber of trials the treatment resulted in significantly (p <0.05)

more healthy fruit than the control in at least one of the two harvests.yTotal number of trials the material was tested.

Quadris Top

(Azoxystrobin & Difenoconazole)

• Applied 4 time (twice each in spring and fall) each on 5 different cultivars of citrus

• Diplodia levels

– Significantly reduced in ‘Early Gold’ orange and ‘Murcott’ tangor

– Tended to reduce in ‘Midsweet’ orange

– No significant differences for ‘Navel’ orange and ‘Ray Ruby’ grapefruit

• There was a consistent positive correlation between Diplodia infection and fruit drop

Zhao et al., 2016

Conclusions• Benlate and Topsin

= best, but no longer available

– Efficacy unknown in HLB era

• Fludioxonil products (Scholar & Switch – not

registered) = occasional control

– Efficacy unknown in HLB era

• Quadris Top = intermittent control under HLB

conditions

• Further work is needed

Pesticide Residues & Fruit

Marketability

• Maximum Residue Limits (MRLs)

– Represent the legal tolerances for residues of

different chemicals (often pesticides) on fruit &

vegetables

– Country specific

FL Fresh Grapefruit Shipments

Source: FDOC-EMRD

0%

10%

20%

30%

40%

50%

60%

1987 1992 1997 2002 2007

Domestic Canada

Europe Japan

Other Pacific Rim Other

Source: FDOC-EMRD (Economic Market and Research Department)

2013

3%

8%

20%

42%

27%

MRLs & Different Countries

• A variety of MRLs for different countries greatly

complicates pest control choices for growers and

packers

• Japan (2006)

– Implemented positive list for MRLs

• EU (2008)

– MRL Harmonization Regulation (EC) No 396/2005

MRLs & Different Countries

• South Korea

– Now switching to a positive list system

• China

– Moving to a positive list system

• Taiwan

– Has many missing MRLs (backlogged) and a

restrictive sanctions policy

MRLs & Different Countries

• Industry vigilance is required when MRLs for

export markets are lower than U.S. MRLs

– Especially critical because countries change

MRLs periodically

– Limited knowledge of how fast residues of various

compounds decline under different

production/postharvest conditions

Secondary Standards

• Even more confusing can be individual buyer residue tolerances that are more restrictive governmental MRLs

– These include food processors

• Such tolerances are not widely reported, but must be obtained through communication directly with the buyer

– Close and frequent communication with buyers is essential

http://irrec.ifas.ufl.edu/

postharvest/

GlobalMRL.com

Thank You!