Observations on pests and diseases affecting a eucheumatoid farm in China

Pests and diseases of eucheumatoid farming were studied in Lian Bay, Hainan Province, China, from March 2009 to December 2013. Neosiphonia savatieri, ice-ice disease, and the herbivorous fish Siganus fuscescens were found to be the dominant pests and disease. Infections of N. savatieri increased severely in May 2009 and especially so in August 2009. Then, they remained severe the whole year round, until all the Kappaphycus spp. in the bay was wiped out by October 2010. The outbreak pattern of ice-ice disease was the same as that for N. savatieri. Based on our results, the period mostly from May to August and also into October was the period of frequent outbreak of the epiphyte and ice-ice disease at this Kappaphycus spp. farm. Different from the Kappaphycus spp., Eucheuma denticulatum showed more resistance to N. savatieri and ice-ice disease at the same time and location. A reduced occurrence of N. savatieri and ice-ice disease infections in Kappaphycus spp. was observed when Kappaphycus spp. were co-cultured with E. denticulatum during July-August but not during September-October. The fish S. fuscescens swarmed into the bay from the outside sea from April to May, when the seawater temperature increased to above 26 A degrees C. Interestingly, the S. fuscescens usually prefer N. savatieri to Kappaphycus alvarezii, and they grazed on K. alvarezii only after the amount of N. savatieri became insufficient to meet their needs. From these observations, we suggest managing the S. fuscescens with different nets at different seasons but not bombs and poison.