Tree injection—also known as trunk injection or stem injection,—is a method of targeting a precise application of

pesticides Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampric ...

, plant resistance activators, or fertilizers into the

xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...

vascular tissue of a tree with the purpose of protecting the tree from pests, or to inject

nutrients A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

to correct for

nutrient deficiencies Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues ...

. This method largely relies on harnessing the tree's vascular system to translocate and distribute the active compounds into the wood, canopy and roots where protection or nutrition is needed. Tree injection is currently the most popular method for control of damaging insects, pathogens, and nematodes in landscape tree care.

Description

Trunk injection has been developed primarily for use on large size trees and in proximity of urban areas where ground- and air-spray applications are impractical due to substantial drift-driven pesticide losses or not allowed due to potential human exposure. However, the prime driver of tree injection use has been a wide spread need for control of many invasive tree pathogens and insects pests. The most infamous examples are that of ''Ophiostoma'' fungi that cause

Dutch Elm Disease Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into Americas, America ...

(DED) and insect

Emerald ash borer The emerald ash borer (''Agrilus planipennis''), also known by the acronym EAB, is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash species. Females lay eggs in bark crevices on ash trees, and larvae feed undern ...

(''Agrilus planipennis'') which have specific biologies that lead to severe internal damage of wood and thus tree death, and which make their management extremely difficult or inefficient with classical pesticide application methods. Trunk injection for tree protection is viewed as environmentally safer alternative for pesticide application since the compound is delivered within the tree, thus allowing for selective exposure to plant pests. In landscapes and urban zones trunk injection significantly reduces the non-target exposure of water, soil, air, and wildlife to pesticides and fertilizers. In the last 20 years, tree injection is gaining momentum with the development and availability of new, efficient injection devices and injectable and xylem mobile formulations of pesticides, biopesticides and nutrients. Trunk injection works by adding a

water soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

chemical directly into the lower stem of the tree structure.

Applications

A number of newly occurring and fast spreading invasive insect pests and diseases such as Polyphagous Shot Hole Borer (PSHB) ('' Euwallacea'' spp.), which can vector plant pathogenic fungus ''

Fusarium ''Fusarium'' is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil mi ...

euwallaceae'', and Sudden Oak Death (SOD) caused by an

Oomycete Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...

Phytophthora ramorum ''Phytophthora ramorum'' is the oomycete (a type of protist) plant pathogen known to cause the disease sudden oak death (SOD). The disease kills oak and other species of trees and has had devastating effects on the oak populations in California a ...

'', establish the use of trunk injection as the most efficient tree protection technique in landscapes and urban forestry. In the past and recently, trunk injection of pesticides and plant resistance activators has been investigated in agriculture for control of pathogens and insect pests on fruit tree crops and grapevines. The most investigated are diseases and pests of avocado, apple, and grapevine, such as Phytophthora root rot of avocado ''

Phytophthora cinnamomi ''Phytophthora cinnamomi'' is a soil-borne water mould that produces an infection which causes a condition in plants variously called "root rot", "dieback", or (in certain '' Castanea'' species), "ink disease". The plant pathogen is one of the wo ...

'' and avocado

thrips Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...

''Scirtothrips perseae'',

fire blight Fire blight, also written fireblight, is a contagious disease affecting apples, pears, and some other members of the family Rosaceae. It is a serious concern to apple and pear producers. Under optimal conditions, it can destroy an entire orchard ...

Erwinia amylovora Fire blight, also written fireblight, is a contagious disease affecting apples, pears, and some other members of the family Rosaceae. It is a serious concern to apple and pear producers. Under optimal conditions, it can destroy an entire orchard ...

'' and

apple scab Apple scab is a common disease of plants in the rose family ( Rosaceae) that is caused by the ascomycete fungus ''Venturia inaequalis''. While this disease affects several plant genera, including ''Sorbus, Cotoneaster,'' and '' Pyrus'', it is m ...

Venturia inaequalis ''Venturia inaequalis'' is an ascomycota, ascomycete fungus that causes the apple scab disease. Systematics ''Venturia inaequalis'' anamorphs have been described under the names ''Fusicladium dendriticum'' and ''Spilocaea pomi''. Whether ''V. in ...

'', oblique banded leaf roller ''

Choristoneura rosaceana ''Choristoneura rosaceana'', the oblique banded leaf roller or rosaceous leaf roller, is a moth of the family Tortricidae. It is native to North America, but has been accidentally introduced into other parts of the world. The wingspan is 7.5– ...

'' and

codling moth The codling moth (''Cydia pomonella'') is a member of the Lepidopteran family Tortricidae. They are major pests to agricultural crops, mainly fruits such as apples and pears. Because the larvae are not able to feed on leaves, they are highly d ...

''Cydia pomonella'', and grapevine downy mildew ''

Plasmopara viticola ''Plasmopara viticola'', the causal agent of grapevine downy mildew, is a heterothallic oomycete that overwinters as oospores in leaf litter and soil. In the spring, oospores germinate to produce macrosporangia, which under wet condition release ...

'' and powdery mildew ''

Uncinula necator ''Uncinula necator'' (syn. ''Erysiphe necator'') is a fungus that causes powdery mildew of grape. It is a common pathogen of Vitis species, including the wine grape, ''Vitis vinifera''. The fungus is believed to have originated in North America ...

''. Apple trees are especially interesting as a research model in agriculture since it is known that apple production requires intensive spray schedules for control of pathogenic fungus '' V. inaequalis'' with as many as 15-22 sprays of fungicides per season in humid climate. Trunk injection of pesticides is considered as an option for precise compound delivery which will reduce the negative impact of drift-driven pesticide losses in the environment, that occur after aerial or ground spraying of pesticides. Besides negative consequences of frequent pesticide applications in the environment, stem injection of grapevines is investigated in viticulture for control of pathogens with difficult biologies which infect and destroy woody tissues and that cannot be controlled efficiently by canopy spray applications of fungicides. To increase the efficiency of injected compounds in trees and vines, important considerations are plant anatomy, weather and soil conditions, tree physiology processes, spatial and temporal distribution of injected compound, and the chemical properties of injected compound and formulation.

References

{{Reflist, 30em Forestry