230 Nebraska State Horticultural Society. 



TWO DISEASES OF PINES. 



By G. W. Pearson. 



This paper will discuss only two pine diseases, namely, the "damp- 

 ing off" disease, and a new leaf disease which has, as yet, no recognized 

 name. Both of these diseases attack pines in their seedling stage, and 

 both are causing more or less trouble in growing pine seedlings in this 

 state. 



THE "DAMPING OFF" DISEASE. 



The disease commonly known as "damping off" is very destructive 

 to young pines from the time they first come up until they are three or 

 four weeks old, there being comparatively little damage after they are 

 one or two months of age. On the forest reserve at Halsey, the Jack 

 Pine has proven to be the most susceptible, as high as 75 per cent of the 

 seedlings in Jack Pine beds being lost in some cases, while, of the Bull 

 Pine, only about 10 per cent are lost. 



The disease manifests itself by the sudden wilting of the young 

 plants. After examination it is found that the trouble is caused by a 

 fungus which attacks the stem just above the surface of the soil, de- 

 stroying the fundamental tissue, and thus cutting off the water supply 

 from the upper portion of the plant. The work of the fungus is very 

 rapid, an entire bed often being destroyed in a few days. In the nurseries 

 at Halsey 75 per cent of the seedlings in a Jack Pine bed have been 

 destroyed in a single day. 



Several fungi are known to cause "damping off," but the most 

 common one is Pythiuni debaryanum. This is normally a saprophyte, 

 living upon decaying organic matter in the soil, but when the mycelium 

 comes in contact with the tender tissues of certain young plants, it be- 

 comes a facultative parasite. The fungus reproduces both sexually and 

 asexually. Most of the conidia germinate immediately after they are 

 formed, but sexual spores, and, even some of the conidia, undergo a 

 resting stage, and may lie in the soil for several months before germi- 

 nating. Most soils contain either the mycelium or resting spores, and 

 therefore seedlings are liable to attack whenever conditions are favora- 

 ble for the growth of the fungus. 



