ROOT COLLAR EXCAVATION WITH TRICHODERMA INOCULATIONS AS A POTENTIAL MANAGEMENT STRATEGY FOR HONEY FUNGUS (ARMILLARIA MELLE A)
Arboricultural Journal, The International Journal of Urban Forestry
Honey fungus (Armillaria mellea) is an important pathogen that can cause severe damage to infected trees and other plants. In this study we investigated the effect of air-spading and/or inoculation with a bio-control fungus as controls for honey fungus. Air-spading uses compressed air to de-compact soil while causing minimal disturbance or damage to the root system. Air-spading can also use compressed air to permanently remove soil from the base of the tree trunk to the depth at which main
... at which main roots originate, a technique known as root collar excavation. The bio-control fungus Trichoderma harzianum strain (Trade name Trianum) is a root symbiont that is known to protect host plants from a range of pathogenic fungi. Raised beds were constructed and artificially inoculated with A. mellea while non-A. mellea infected beds acted as controls. One year later A. mellea infected raised beds were subjected to one of the following treatments i) no treatment ii) air-spading, iii) air-spading + T. harzianum or iv) T. harzianum only. The effectiveness and longevity of air-spading and T. harzianum was determined by potting up strawberry plants cv Cambridge favourite (highly susceptible to honey fungus attack) at month 6, 12, 18 and 24 after treatment. A. mellea infection was then quantified at day 90 after potting up by assessing visual by plant condition, leaf chlorophyll fluorescence Fv/Fm, leaf chlorophyll content (SPAD) values and fruit yield per plant. Air-spading A. mellea infested soil with and without T. harzianum resulted in a two year protective period in which A. mellea failed to re-infect strawberry plants. In addition, failure to re-isolate A. mellea from media after air-spading indicates the air-1 Dr ). 268 ARBORICULTURAL JOURNAL spading process may have eradicated A. mellea from the infected raised bed. Some degree of protective properties against A. mellea was confirmed when applying T. harzianum alone. For example, based on visual plant condition, application of T. harzianum reduced A. mellea severity by 12.5-65.7% over the two year study. Findings of this study strongly indicate that air-spading followed by inoculation with T. harzianum appears to offer promise as a joint cultural/bio-control strategy for the management of A. mellea. Results however, should be interpreted with some degree of caution as experiments were conducted under controlled conditions where soil conditions may vary from that in a woodland, forest or urban environment.