Preliminary survey of pests and diseases of eucheumatoid seaweed farms in the Philippines

Farmed eucheumatoids are the top aquaculture commodity in the Philippines, contributing more than 60% of total national aquaculture production by volume. Despite significant production losses observed in recent years due to pests and diseases, data relating to the temporal and spatial geographic distribution, seasonality, prevalence, and etiology of these critical problems at the farm level are lacking. Here, we assessed the prevalence of pests and diseases at 16 farm sites within several major seaweed growing areas, including Luzon (Palawan), Visayas (Bohol), and Mindanao (Zamboanga City, Davao del Norte, and Tawi-Tawi). Prevalence of pests and diseases were recorded by assessment of individual seaweed plants in situ, comprising >= 5% of the total number of seaweed plants on each farm. Results from this survey revealed ice-ice disease (IID) at all sites, albeit at low prevalence rates of below 25%, the exception being one site where prevalence was 100%. No significant difference in the prevalence of IID was found between farms in shallow (approximate to 0.5 m during low tide) and deep water sites (depths exceeding 4 m during the lowest tide) (p>0.05). Moderate prevalence (26-50%) of the macro-epiphyte pests Sargassum and Ulva was reported in Luzon. Further, epiphytic filamentous algae (EFA), black spots, and evidence of grazing were recorded in several farms with low prevalence (0.2-11.2%). The three farms with the highest prevalence of IID and EFA were evaluated to determine the severity of cover on the thallus of infected plants. A very high severity of IID (76-100% coverage) was observed on the secondary and primary branches, while for EFA, low severity (<= 25%) was found in all regions of the thallus. Our results suggest the widespread occurrence of yield-limiting diseases and pests affecting eucheumatoid farms in the Philippines. Strategies for the diagnosis, surveillance, and management of yield-limiting pests and diseases are needed to ensure maintenance and sustainable expansion of this important aquaculture sector in the Philippines.

Automated summary

Farmed eucheumatoids are the top aquaculture commodity in the Philippines, but have suffered significant production losses in recent years due to pests and diseases. The study found ice-ice disease to be widespread across all sites, although prevalence rates were generally low. Further strategies for diagnosis, surveillance, and management are needed to ensure the sustainable development of this important aquaculture sector in the Philippines.