Management of citrus establishment with white and

red-dyed kaolinChristopher Vincent, Myrtho Pierre

civince@ufl.eduTree Ecophysiology

Citrus Research and Education CenterUniversity of Florida, USA

Horticulture - Particle films

• Properties• Reflection• Shading• Redistribution of light

within the canopy• Reduce sunburn • Increase whole canopy

photosynthesis• Increase leaf level water

use efficiency• Kaolin

Kaolin effects on ACP• Physical deterrence• Optical “repellant” • Some colors more effective than

natural white

Objectives• Compare red-dyed kaolin,

undyed kaolin and foliar insecticides for:• Effects on ACP• Effects on infection rate• Effects on growth, photosynthesis,

and horticultural characteristics• Subsequently interactions with

disease.

Study design• New planting from day 1

• Randomized complete block • 6 blocks• Location

• Plots• 20 treated trees• 6 data trees

• Treatments• White kaolin – Surround applied “as needed” +

”sticker” adjuvant (SKH)• Red kaolin – dye added with binding agent + ”sticker”

adjuvant• Foliar insecticide – Calendar and psyllid pressure basis• Untreated control – systemic insecticides for leaf miner

control

• Variables• Reflectance• ACP counts weekly

• All ACP on each tree• PCR CLas detection quarterly • Stem caliper• Flowering• Gas exchange

• Photosynthesis, stomatal conductance, transpiration• Amax : with PPFD 1,000 µmols m-2 s-1 , VPD -1.6 kPa, 400

ppm CO2

1 Plot (1 Replication of 1 Treatment)

Results – Stem Diameter

Treatment

Mean flowers per tree

Foliar Insecticide 5.8 bRed Kaolin 8.2 a

Untreated Control 0.4 cWhite Kaolin 3.3 b

10

15

20

2017-07 2018-01 2018-07date

Dia

met

er (m

m) treatment

Foliar insecticide

Red kaolin

Untreated control

White kaolin

a

b

a

b

Results - Photosynthesis

0

5

10

Foliar Insecticide Red Kaolin Untreated Control White KaolinTreatment

A (µ

mol

m-2

sec

-1)

Results – ACP counts

0

5

10

15

20

May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18

Mea

n ps

yllid

cou

nt p

er p

lant

Treatments Foliar Insecticide Red Kaolin Untreated Control White Kaolin

2017 2018

Floral flush

Results – ACP –Dec 2017

Insectide Control

Untreated Control

White Kaolin 95 97

Red Kaolin 97 98

0.0

0.5

1.0

1.5

Foliar Insecticide Red Kaolin Untreated Control White Kaolin

Mea

n ps

yllid

cou

nt p

er p

lant

a

b

cd

Percent control of ACP in kaolin treatments vs. chemical or untreated controls

0

1

2

Foliar Insecticide Red Kaolin Untreated Control White Kaolin

Mea

n ps

yllid

cou

nt p

er p

lant

Results – ACP -as of August 2018 b

c

80% percent control of ACP in kaolin treatments vs. untreated control

a

c

0.00

0.25

0.50

0.75

1.00

Apr 2017 Jul 2017 Oct 2017 Jan 2018 Apr 2018Treatment

Pro

porti

on o

f pla

nts

infe

cted

treatmentFoliar Insecticide

Red Kaolin

Untreated Control

White Kaolin

Results – CLas infection

b

aa

a

b

b

a

b

c

c

b

a

Preliminary conclusions

• Kaolin particle films improve ACP management and reduce disease pressure• Red-dyed kaolin superior to date

• Both red and undyed kaolin films increase growth• Photosynthetic increase lesser in red• No difference in overall growth

Future Questions, Next Steps

• Kaolin• Continued long-term field evaluation• Different light qualities (dye colors)• Effects on HLB symptoms vs. CLas transmission

• Effects of color treatments on acclimative photochemistry*infection

• Whole canopy vs. leaf-level water relations• Stickers/rainfastness

• Tree architecture• Flush phenology

Thank you!

Questions?

Results - reflectance

0

25

50

75

100

400 600 800 1000Wavelength.min

Reflectance.mean

Treatment Control

Red Kaolin

White Kaolin

-20

-10

0

10

400 600 800 1000Wavelength.min

value

variabledelta.red

delta.white