Main diseases of Aloe barbadensis Miller in Bali

Aloe (Aloe barbadensis Miller) has been planted in Bali since 2006 with the total area of 170 hectares. The leaves of this plant is processed into gel for further use such as pharmaceutical, food and beverage, cosmetic etc. During the plant growth in the plant field, there are several diseases that have been found to be associated with aloe plants, however, there is no information available on the main disease and the cause of the disease. This research was conducted in order to know the main diseases associated with the aloe plant and the causal agents that are responsible for the diseases. This study was done from January to June, 2010 in five agencies in Bali, namely Buleleng, Karangasem, Bangli, Gianyar and Badung. Three observation points were determined in each regency, except for Buleleng Regency,whereas only one observation point was determined. Observation of the disease was done by evaluating 20% of the total plant population in each observation point to determine the disease occurrences. For identification of the causal agent of the disease, plant samples were collected from diseased-plants. Koch's postulate procedure was applied to determine the causal agent of the disease. The first main disease found in aloe plantation was the leaf rot disease with the occurrence by 7.04% and the second one is black spot disease with the occurrence by 4.64%. There are four species of fungi isolated and identified from the diseased-plants, namely Fusarium sp., Cladosporium sp., Colletotrichum sp., and Helminthosporium sp. Among these fungi, only two fungi i.e. Fusarium sp., and Cladosporium sp. can infect aloe plant or artificial inoculation and produced the same symptom as found in the field, while two fungi i.e. Colletotrichum sp., and Helminthosporium sp. could not infect aloe plant. Fusarium sp. was confirmed as the cause of the leaf rot disease while Cladosporium sp. was the cause of black spot disease.