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 colored or water-soaked spots symptom occurred. The spots darken and coalesce into larger necrotic patches and the leaf will drops. The disease can be minimized by spacing the seedlings more widely, maintaining good drainage and avoiding excessive watering in the nursery. Remove the infected seedlings. Use the sterilized 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
1.3 WHITE ROOT DISEASE
The white root disease in durian are caused by Rigidoporus lignoses a type of fungi. This soil-borne disease occurred 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 color 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. THANKS FOR THE INFORMATION.
|At durian farm in Muar, Johor.|
(1 January 2013)
(1 January 2013)