DURIAN (Durio zibethinus) subject to various pests and diseases throughout the year. Attacked of pests and diseases on durian tree started from seedling stage to harvesting stage that cause serious damage if not properly controlled. Durian diseases divided to Seedling and root diseases,Trunk and branch diseases, Foliar diseases and Fruit diseases. This article I would like to share my knowledge about the durian diseases based on various study in Malaysia, Thailand, Indonesia and other growing durian countries.
1) SEEDLING AND ROOT DISEASES
1.1 DIEBACK AND FOLIAR BLIGHT
This disease is caused by the fungus known as Phythopthora palmivora. Loss of seedlings in nurseries can reach alarming level up to 50% loss if not properly controlled. From my own observation in various private nurseries, infected nursery soils are the main cause of disease. Other reason is the excessive watering of shaded plants which provoke the spread of disease. The infection usually begins at the stems and later extends to the leaves and root zones. If the trunk and branches later girdled by the infection, I saw the seedling dieback ensues. The root are rot and the leaves are off coloured or water-soaked spots symptom occurred. The spots darken and coalesce into larger necrotic patches and the leaf will drops.
The disease can be minimised by spacing the seedlings more widely, maintaining good drainage and avoiding excessive watering in the nursery. Remove the infected seedlings. Use the sterilised in the polybeg. Spraying of selected fungicide are suitable to control this disease. Most nursery owner use fungicide such as metalaxyl, cyprofuram, fosetyl aluminium, milfuram or oxydaxyl to control this problem. The use of metalaxyl are common in Malaysia to control this dieback.
1.2 PHYTIUM ROOT ROT
This root rot disease as I know caused by Phytium vexans a type of fungi. The fungi that attack the trunk of durian are known as Phytium palmivora a different species. This root rot disease is not confined to full grown durian tree but also common in seedling in nursery. The attacked root became necrotic at the root tips. Externally the root appear as normal. but internally the cortex becomes dark brown. New shoot are often produced beneath the dieback of the roots completely damage. To control this disease, several measures are recommended. This include the uprooting and burning of infected trees. Construct trenches around the infected tree and always inspect the adjacent trees. The most common measures that I know very practical is by application of fungicide such as Metalaxyl, fosetyl aluminium, propamorcarb hydrochloride and etridiazole. The use of Trichoderma spp are means of biological control. Another possibility is the use of resistant varieties and improve drainage system in the farms.
1.3 WHITE ROOT DISEASE
The white root disease in durian are caused by Rigidoporus lignoses a type of fungi. This soil-borne disease occured if the durian are planted in the area of ex-tapioca (Manihot esculenta) or ex-rubber (Hevea brazilliensis) plantation. The disease are serius for the first six years of durian establishment. The symptoms shown by foliage wilt and changes colour from green to yellow than brown and finally shrivels. The durian tree as I observed usually dies shortly after showing this symptoms. For this disease I can say that "Prevention is better than cure" due to not many alternative to avoid. Farm preparation is important to burn all the debris of rubber, cassava or jungle trees. Remove and burn all the infected tree and prepare holes drenched with fungicide such as Tridemorph , Triadimefen, propoconazole or triazole. Further treatment, it advised to dust the planting holes with sulfur before planting. The construction of isolation trenches around diseases tree can also helps curb the spread of disease.
This nematode are known as Xiphinema (the dagger nematode) is an ectoparasitic nematode. The nematode feed on the apical tips of the feeder roots and damage them. This caused the root tip to swell and stunted the growth. The infected root only one third of the length of the normal roots. This symptoms is a difficult to indicate because similar to the symptoms of lack of nutrient caused by drought. The impact of nematode attack as I know is quite difficult to access. The use of Nematicides may able to reduce the high population of nematodes in the soils. It is better to check the existence of nematode in the durian area for precaution measures.
Visit durian farm at Tangkak, Johor.
(1 January 2013)
(1 January 2013)