Disease Translocation Risk Mitigation – Ganaderma zonatum
Ganaderma Spore Translocation Avoidance Procedures (GSTAP)
Ganaderma zonatum is an incurable disease that affects various species of palms. The mature basidiocarps produce spores that become airborne and that may survive on organic material in soil for long periods of time. To mitigate the risk of disease translocation, it is essential that action be taken to stop the distribution of these spores wherever possible. There is no precise data on exactly how Ganaderma is spread but we do know that spores produced by mature basidiocarps are the likely initialization element and that physical translocation of the spores via a variety of means, natural and unnatural, is the likely vector. The goal of a Ganaderma Spore Translocation Avoidance Procedure (GSTAP) is to stop the movement of the spores until such time as the infected host can be removed from the property. This is a very simple procedure that requires a degree of diligence and little else.
One very important point; it is most likely that the spoors that invaded the currently infected palm came from somewhere fairly near the site. The spoors will move on air currents but we do not consider it likely that they will move any significant distance by that means. A more likely cause of broader spoor distribution would be site translocation on the shoes/boots of workers operating near an infected palm that is demonstrating one or more mature basidiocarps. Finding the original spoor source and taking steps to eradicate that source will go a long way toward avoiding additional disease translocation events.
Ganaderma Spore Translocation Avoidance Procedure (GSTAP)
1. Host species palms growing on or near sites where Ganaderma has previously been identified should be visually inspected on a bi weekly basis for the presence of emerging basidiocarps. These are mushroom-like fruiting bodies that are also known as “conks”. Each basidiocarp may produce millions of spores which will be shed primarily from its underside and contaminate the soil under & around the conk. The spores will also float on air currents potentially causing a translocation of the disease to an uninfected host palm. The conks may emerge at any point along the trunk but they are most commonly found near ground level just above the root/trunk interface. Careful inspection from the top of the trunk to the bottom is required.
2. Where conks are observed, immediately drench the entire conk with undiluted Chlorine Bleach and if possible & permissible, perform a soil drench on the soils within 18” of the conk using a 50/50 mix of Chlorine bleach and water. Bleaching the basidiocarp will act to kill its spores and will cause a pronounced darkening of the conk but it will not kill nor even harm the disease inside the palm. Performing the soil drench will not necessarily eliminate all of the spores in the soil; it will only destroy those that it comes into contact with. This being the case, we consider this to be a sensible translocation risk mitigation step but we do not believe it likely that a 100% kill will be achieved. In infected palms, the conks will continue to emerge and should be bleached as soon after emergence as possible to avoid spoor distribution and contain the disease within the already infected palm.
3. Remove the host palm from the site as soon as is possible. Prior to removing the palm, bleach any existing conks and then carefully separate them from the trunk and contain them in a zip lock bag. Once the conks are removed, load the trunk(s) and dispose of them at a landfill. Leaving the infected host in a “dead” pile at the back of a nursery or landscape contractor’s yard is a very bad idea; new conks will emerge and spoor distribution will occur.
4. Though professional opinions vary rather widely on the subject, here at Groundworks we are willing to install and warranty new host species palms in locations where Ganaderma infected palm(s) have been recently removed. When operating under these circumstances, we employ a specialized site preparation and re-installation procedure that I developed for use on sites where infected palms had previously been growing. We have susceptible host species palms planted in such sites and in many cases, the new palm(s) have been onsite in excess of 10 years without a reinfection event occurring. We have achieved a 100% success rate (zero incidence of re-infection) using this protocol but would not plant into a Ganaderma site without employing these special measures. If we were to, we believe that reinfection is likely.