Nguyen Sy Giao
Nguyen Thi Nham
INTRODUCTION
The so-called “weak-yellow disease” is a very serious disease for P.merkusii seedlings in the nursery. This disease could cause the death of from some ten-thousands to one million seedlings in a production organization wich was main reason why many areas could not fulfill their yearly planting plan for P.merkusii. During the period 1971 to 1976, the Forest Research Institute carried out research work on this disease.
RESEARCH CONTENT AND REMARKS
1. Investigate symptoms of the disease and suggest a new name. Because the disease has two main features: yellow crown and weak growth, we suggest calling it “weak-yellow disease” of P.merkusii seedlings.
2. Causes of disease : By carrying out observations on the root system of young pine seedlings in some years at many locations, it was shown that most seedlings suffering weak-yellow disease had no mycorrhiza (98.5%). On the contrary, most of seedlings having green crowns and normal growth showed existence of mycorrhiza (86%). Experiments to cause artificial disease by eliminating mycorrhiza in soil with 3 different methods have shown that disease was present in all cases. On the contrary in the control, seedlings were grown normally. Based on that fact, it was concluded that one of the main reasons for this weak-yellow disease on P.merkusii seedlings is that their root systems did not have mycorrhiza in symbiosis.
Latest news
- Project: Study on integrated management of insect pests and diseases on Docynia indica in northern Vietnam
- Project: Study on integrated pest management of major leaf insect pests and stem borer beetles in Acacia hybrid, A. mangium and A. auriculiformis in Vietnam
- Project: Research and develop an integrated management program for control of cinnamon pests in some main cinnamon growing areas (Northern mountainous region and Quang Nam province)
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- Project "Research on selection of varieties and intensive afforestation techniques of Prunus arborea (Blume) Kalkman for providing lager timber in the Northeast and Northwest regions, Vietnam"
Oldest news
- species and provenance trials of pines (1981 - 1985)
- study on the establishment of a site table for pinus kesiya in lamdong (1983 - 1985)
- research on the increment law for thinning and maintenance of pinus merkusii forest
- study on soil mixtures used as the medium for raising p.merkusii seedlings for large-scale production (1972 - 1975)
- preliminary research on use of some pure symbiotic fungi to make mycorrhiza with p.merkusii seedlings (1976 - 1977)
