Trunk injection has been highly effective at managing specific pest problems, such as Dutch elm disease, in urban trees and forests across the northeastern United States. However, the technology is inherently expensive, both in terms of equipment and expertise as well as the cost of high specification formulations able to successfully enter a tree’s vascular system. Based on recent experience, trunk injection also has potential to battle Red Palm Weevil in southern Europe, a pest which has spread to the region from Asia and is now present in Italy, southern France, and Spain.
Insecticidal sprays are the main form of treatment though these are problematic for trees serving an ornamental function in public spaces. Trunk injection on the other hand is able to overcome this problem whilst maintaining efficacy. Relevant suppliers of this product include Chemjet (Australia & UK), Fertinyect (Spain), and Arborprof (Italy).
Trunk Injections and Agricultural Biotechnology
Chemjet is the largest company able to deal with Red Palm Weevil through trunk injection, though their equipment is largely used for protection of root rot in avocados. Fertinyect has the largest market share in Europe and the Middle East for Red Palm Weevil, and also has distributor deals in the United States. Arborpof supplies both canisters for purchase and use by the general public as well as services that deploy a high pressure (3 bar) cylinder system implemented by trained professionals able to immunize a tree in just a few minutes.
The Fertinyect system is by far the easiest to use. A small hole drilled quickly into the side of the tree allows the canister outlet to be inserted; a squeeze by hand gets the liquid moving and the pressure gradient created through evaporation of water from tree leaf stomata does the rest. In time, the tree’s natural defense system will cover the hole and protect it from infection or pest invasion.
The Red Palm Weevil (Rhynchophorus ferrugineus) is a particularly large beetle up to 4 cm long with an appetite for the inner core of young palm trees. The adults feed on palms, but most of the damage is caused by beetle larvae burrowing into the center of the palm trunk. It is the soft inner trunk of palms that allow the grubs to burrow so deep; a palm is in fact a very large plant, and does not have the hard inner core associated with the sapwood of softwood and hardwood trees.
An infested palm can be identified visually through signs of uneven wilting, as opposed to the uniform wilting associated with dehydration or nutrient deficiency. Infestation can also be detected through bioacoustics, which uses high sensitivity microphones in combination with machine learning to identify the pest. It is also possible to identify the palm weevil through the use of specially trained dogs. Undetected and untreated, the palm will eventually die, no matter if an agricultural palm (such as a date palm) or ornamental species.
Trunk injection technology undergoes continuous research. Problems such as tree damage following injection have been surmounted through plug-less technology and five or six groups of researchers worldwide are looking at new formulations able to take existing biological and chemical active ingredients used in sprays and engineer them for trunk injection applications. Such research strives to develop formulations with solubility and viscosity similar to tree sap to ensure effective injection.