Trunk Injection: Difficulties and Considerations

Ute AlbrechtUF/IFAS Southwest Florida Research and Education Center

ualbrecht@ufl.edu

2020 Florida Citrus Grower’s Institute

What is trunk injection?o A targeted application of pesticides, plant

resistance activators, fertilizers, or other materials into the stem or trunk of a woody plant as an alternative to spraying or soil drenching (“Endotherapy”).

o Injection occurs into the xylem (not the phloem), from where the materials are then distributed throughout the plant with the transpiration stream.

Advantages of trunk injectionso Precise delivery of crop protection materialso Elimination of spray drifto Reduced risk for worker exposureo Reduced risk for non-target organismso Reduced pesticide load into the environmento Lengthening of the duration of time that applied

materials are biological active

Trunk injection useso Insects (leaf beetles, leaf hoppers, leaf miners, lace

bugs, psyllids, mites, scales, aphids, thrips, whiteflies, mealy bugs, etc.)

o Nematodes (wood nematodes)o Fungi (powdery mildew, blight, rust, scab, etc.)o Bacteria (bacterial blight, bacterial leaf scorch, Xylella)o Phytoplasmas (lethal yellows/bronzing)

o Imidacloprido Emamectin benzoate o Acetamiprid o Abamectin

Materials used for injectionSuppression of insects, mites, and nematodes of ornamental trees, non-bearing fruit and nut trees, coniferous trees, palm trees, and shrubs.

Residential and commercial landscapes and other private and public areas, urban areas, forest areas, and other uncultivated non-agricultural areas.

o Propiconazoleo Phosphoric acid

Materials used for injectionSuppression of fungal diseases

Non crop-bearing ornamental trees, large woody shrubs, and palms in urban environments and residential areas.

o OxytetracyclineSuppression of bacterial and Phytoplasma diseases

o Nutrientso Growth regulators

Plant growth

Diseases treated by trunk injectionsForestryo Oak wilt disease (fungal disease affecting the xylem) o Dutch elm disease (fungal disease affecting the xylem) o Emerald ash borer (feeds on the bark)o Pine bark beetle (feeds on the inner bark)o Sudden oak death (Phytophthora)

Diseases treated by trunk injectionsAgricultureo Apple - scab and fire blighto Avocado - root rot, thripsViticultureo Grapevine downy and powdery mildewOrnamentalo Palm lethal yellowing/bronzing

Methods of injection

Most technologies are drill-based. Few are no-drill (needle)-based. All require relatively large injection holes.

Drilling (→ large holes)o Risk of permanent damage to the sap wood (embolisms,

callusing and compartmentalization of the vascular system)o Loss of chemicals due to untargeted nature of applicationo Easy entry side for pests and diseases o Reduced tree vitality in the short and long term

Needle or blade injection (→ smaller holes)o Less risk of permanent damage to the sap woodo More targeted application to the active zone of transport

Drill vs. needle injection

Fast high-pressure injection

Slower medium pressure injection

Methods of injection

Low or no pressure transfusion

Concerns about any type of injectiono Logistical problems (time, labor, cost)o Wounding of treeso Vessel destruction, cavitation and embolimso Secondary infectionso Impact on long-term tree vitalityo Impact on pollinatorso Residues in fruito Consumer perceptiono Time and resources to get label for use

Tree physiology

Phloemo Made up of living tubes (sieve cells and companion cells)o Transport of sugars and other organic compoundso Transport is bidirectional from source tissue (e.g. leaves)

to sink tissue (e.g. roots and fruits)Xylemo Made up of non-living tubes (vessel elements and tracheids)o Transport of water and nutrientso Transport occurs from roots to stems to leaves

Long distance transport in plants

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Xylemo Passive transporto Driving force is transpiration

Phloemo Active transporto From source tissue (high sugar

content) to sink tissue (low sugar content)

Directions of transport

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Transpiration stream(Xylem)

https://www.anatomynote.com/plants-and-trees/wood-and-tree/tree-sectional-structure-in-detail-layer-structure/

Anatomy of a tree trunk

Anatomy of xylem and phloem

Xylemvessel

PhloemCLas

Xylem and phloem exchange is via the rays

Ray parenchyma

Dye injection studies

High pressure injectionAboveBelow

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Natural uptake through roots

Natural transport is in the outer zones of the trunk, close to the bark.

Comparison

Injection Root uptake

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High pressure injection

Injection site Above injection site

Longitudinal trunk section Immature fruit

Phloem

High pressure injection

Uptake studies

Low pressure transfusion

0.5 cm 2.0 cm

Uptake is influenced by the depth of delivery.

Low pressure vs passive transfusion

More material is taken up when pressure is applied.Low pressure Passive

Uptake volume

More injection ports increase the volume that can be delivered into the tree.

Safranin O

Acid fuchsin

Mobility depends on the chemical properties

Mobility depends on the chemical properties

Trunk injury

Wound healing

Closed Open Mostly closed but bark cracking

NecroticOpen, bark cracking

Width: 3.175 mm (0.125” Depth: 5 mm (0.2”)

Wound healing

Bark cracking occurs frequently.

Take home messageso CLas resides in the phloem (not in the xylem).

o Trunk injections deliver materials into the xylem (not the phloem) from which the materials are distributed through the tree by the transpiration stream.

o Different chemicals will vary in their mobility through the xylem and translocation to the phloem.

Take home messageso Trunk injections will injure a tree.o Phytotoxicity may occur.o Xylem vessels may embolize.o Secondary infections may occur at the injection site.o One-time injections will not prevent recurrent insect

colonization and pathogen infections.

The impact on long-term tree vitality or viability is unclear, especially when conducting repeated injections.

Development of an automated delivery system for therapeutic materials to treat HLB infected citrus

USDA-NIFA-SCRI-006650

Funding

PD/Co-PDsDrs. Ozgur Batuman, Yiannis Ampatzidis, Ute Albrecht

(UF/IFAS SWFREC)CoPIs

Drs. Fernando Alferez (UF/IFAS SWFREC), Tara Wade (UF/IFAS SWFREC), Nabil Killiny (UF/IFAS CREC), Amit Levy (UF/IFAS CREC),

Veronica Ancona (Texas A&M), Louise Ferguson (UC Davis)

Leigh Archer (PhD student)

Ute AlbrechtUF/IFAS, Southwest Florida Research and Education Center

ualbrecht@ufl.edu