Experts Battling to Save Coconut Palms in Hawaii pg.3
Many diseased palms have been observed in wet windward areas of Kauai, the Big Island and Oahu and Maui. Growers should avoid collecting coconut-planting material from these areas. Since mature palms may be infected, yet remain without symptoms for many months, careful selection of clean nuts and healthy seedlings and plant stock is necessary.
Stock plants or young seedlings should be grown in relatively dry areas to minimize establishment of the pathogen on new plants. Because the epidemiology of the disease in Hawaii is not known, the exact means by which the pathogen spreads is not specifically known.
Based on studies of other Phytophthora diseases however, wind-driven rain, insect feeding and movement or activities of other small animals are probably important factors in the spread of the disease. Moisture strongly favors the growth, spore production, spread of the pathogen, and disease development by Phytophthora.
Sexual spores of the pathogen occur in large numbers within diseased husks and trunks. These thick-walled resistant structures allow the pathogen to survive for long periods in a dormant state. The pathogen is seed-borne, as sexual spores are common in the husk of the diseased fruits.
The removal of nut clusters and heavy leaf pruning of large palms have probably aided disease spread. Microscopic spores from diseased tissue will contaminate cutting tools and infect healthy ones during subsequent pruning operations. Furthermore, wounding the stem base by cutting off green fronds exposes highly susceptible plant tissue to pathogen infections.
When feasible, trimming should be done during dry weather. Tools should be cleaned, then immersed in a disinfectant after trimming operations on each are completed, especially at sites known to have the disease.
