Seeing the Light: An Update on the Use of Particle Films and Shading to Manage Citrus and Citrus Pests

Christopher Vincent, civince@ufl.eduAnirban Guha, anirbanguha@ufl.edu

Tree Ecophysiology Lab Citrus Research and Education Center University of Florida

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Main points• Stay cool: High light and leaf temperature

combine to reduce citrus growth and yield

• Shade reduces stress of citrus trees

• Horticultural goal depends on balancing stress with flowering and fruit development

• In establishment period kaolin particle films can:

• Increase growth and yield • Reduce psyllids• Delay HLB infection

• Red-dyed film is optimal

• Particle films and red colorant are commercially available

Kaolin

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https://redcrossphillyblog.wordpress.com

Citrus and Light

• High light leads to high leaf temperatures• Mild shade keeps leaf temperatures down

Leaf

tem

pera

ture

(°C

)

0:00

1:25

2:50

4:15

5:40

7:05

8:30

9:55

11:2

012

:45

14:1

015

:35

17:0

018

:25

19:5

021

:15

22:4

0

0S 50S

98°F

113°F

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Time (hh:mm)

Feral citrus in central Florida• No psyllids found in multiple

observations• Only 3 of 60 trees found to

be HLB infected • No HLB symptoms• Greater shade improved

photochemical responses

Full study:

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https://link.springer.com/article/10.1007/s00468-021-02147-2

Taking it to the field

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(2018 Oct – till date)

Hamlin trees grafted on Swingle citrumelo

2019 20200

20

40

60

80

2019 20200

5

10

15

Fruit no per tree Fruit weight (kg) per tree

No.

tree

-1

Kg tr

ee-1

Yield

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This year (2021) – Flowering & fruit drop data

• Where is the balance between stress, growth, and yield?

• What kinds of shading are useful?

• What about impacts on psyllids?

Photo courtesy of Graham Berry

Can shade become part of citrus production?

Netting structures in South Africa

Citrus grown under nets in South Africa

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Particle films• Properties:

•Reflection•Shading•Redistribution of light within the canopy

• Reduce sunburn • Increase whole

canopy photosynthesis

• Kaolin• Red dye

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While particle film on sweet orange trees, FL

Mandarin tree, Central Valley, CA

Red and white kaolin

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CLas infection

a

b

dc

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Trunk growth

a

b

c

d

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Canopy GrowthJuanpablo

Salvatierra-Miranda

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No insecticide Foliar Insecticide

White kaolin

Cloudpoint data from Agerpoint

Red kaolin

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a

a

bb

ab

Yield

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Lemons – Ventura Co., CA

• Red-dyed formulation ideal:• 35 lbs/acre Surround• 2.5 fl oz Colorback /lb Surround

(87.5 fl oz/acre)• Or equivalent concentration with

100 gal:1 acre.

• Red-kaolin mix superior:• Growth• Yield• Psyllid reduction• CLas infection delay

• Fruit drop?• Does it work the same with

mature trees?

Lessons in using kaolin

Our new paper on psyllid mgmt. with kaolin: Pierre et al. 2021, Crop Protection

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Thank you!Twitter: @treecophys

Website: Treephysiologylab.com

Thanks to Myrtho Pierre, Ronnie Holmes, Dacia Lopez, Juanpablo Salvatierra, Becky Ebert, Nabil Killiny, Lauren Diepenbrock

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