Publications - Faculty - Recently Submitted Faculty Publications 2009

Albrigo - Proc. Florida State Horticultural Society

In-Place Elimination of HLB Infected Trees Through Application of Phytotoxic Chemicals

L. G. Albrigo, Steve Smith, and Kyle Register

Abstract. As part of the scouting procedure for huanglongbing (HLB) affected trees, current recommendations call for removal of the infected trees as soon as possible after each scouting, of which there may be four per year.  Tree removal is labor intensive, costly and difficult to schedule during the harvest season.  An alternative would be to kill the infected trees in-place and remove them at a convenient time and not more than once per year.  Experiments were conducted to determine the effectiveness of herbicides and their method of application for killing mature citrus trees. Canopy sprays that included Remedy (trichlorpyr) were effective while LandmasterII (glyphosate + 2,4-D) did not kill the trees, but both resulted in canopy damage to adjacent trees.  Spraying the inside canopy from under the tree was effective if the spray covered the more extended growth towards the row middle.  Remedy again was more effective than LandmasterII.  Spraying cuts on the four sides of the trunk with concentrated herbicide worked well with Arsenal (imazapyr)  or Clearstand (imazapyr+ metsulfuron methyl), but Remedy, LandmasterII and 2, 4-D alone were not very effective.  Commercialization of this method will probably require a vehicle mounted attachment to make the cuts and spray the chemical.  Tests were also conducted with soil injection of the fumigant Midas (Iodomethane).  This procedure worked fairly well on small to medium size trees, but further testing is needed to increase consistency of tree kill on large trees.  Successful application of the trunk herbicide or soil fumigant method should be cost effective as a replacement for stumping HLB affected trees, but these chemicals are not cleared for use in citrus and require pesticide use labels.