Laurel wilt disease, incited by Raffaelea lauricola, has resulted in the death of more than 300 million laurel trees (Lauraceae) in the United States. One such tree is the commercially important avocado (Persea americana), the second largest tree crop in Florida other than citrus (Citrus sp.). This disease affects the industry in South Florida and two larger avocado industries in Mexico and California have taken notice. Trees succumb soon after infection, and once external symptoms are evident, the disease is very difficult to control and contain as the pathogen can spread to adjacent trees via root grafting. Presently, there is no viable, cost-effective method of early diagnosis and treatment. This study was undertaken to evaluate the use of scent-discriminating canines (Canis familiaris) for the detection of laurel wilt–affected wood from avocado trees. Three canines, one Belgian Malinois and two Dutch Shepherds, were trained and studied for this ability. In addition, prevailing weather conditions were recorded and evaluated to determine their effect on canine performance. The results of this evaluation indicated that canines can detect laurel wilt–affected wood and the laurel wilt pathogen and may be useful in the detection of laurel wilt–diseased trees in commercial groves.
The invasive redbay ambrosia beetle (Xyleborus glabratus) was first detected in Savannah, GA, in 2002. This tiny beetle and its symbiotic fungal partner (Raffaelea lauricola) have led to one of the most devastating new plant diseases in recent times affecting laurel trees (Lauraceae), laurel wilt. In Florida, this devastating disease has also affected the agriculturally important avocado (Persea americana), and once symptoms are visible (i.e., wilting leaves), it is too late to save the infected tree. However, prophylactic systemic treatment with propiconazole can protect the trees from the disease for ≈12 months. This study evaluated the novel approach of using scent-discriminating canines (Canis familiaris) trained on the volatiles of laurel wilt pathogen as a proactive management tool for grove owners. Canine deployments in groves resulted in the detection of 265 presymptomatic avocado trees during two trials. In trial 1, 155 presymptomatic trees were treated with propiconazole and, over the subsequent 14-month monitoring period, 97% remained asymptomatic. In trial 2, the canines detected 100 presymptomatic trees that were not subsequently treated and 22 progressed to wilt within 2–5 weeks, and the remaining trees were removed, thus halting the observation period at 6 weeks. The canines have proven to be an effective proactive management tool.