356 Diseases of Greenhouse Crops 



generally carried from year to year as chlamydo- 

 spores in remnants of infected tissue in the soil or in 

 the compost pile. 



Control, The fact that the harboring of chlamy- 

 dospores in the compost is one of the means by which 

 the causal organism is brought into the greenhouse 

 at once suggests soil sterilization as a means of con- 

 trol. This disease is often carried unconsciously 

 with affected cuttings. From there the sand used 

 for rooting the cuttings becomes infected. If the 

 same sand should be used over again it will infect 

 all cuttings planted there. Where there are no fa- 

 cilities for soil sterilization the grower should make 

 it a practice to use virgin sand every year. How- 

 ever, a safer method is to disinfect the soil with 

 formaldehyde. Reddick recommends the use of 

 1 pint of commercial formaldehyde (40 per cent 

 pure) to 125^ gallons of water. This solution is 

 then used at the rate of 1 gallon to each square foot 

 of bed space. Lime should not be used for violet 

 beds, because lime favors the development of Thie- 

 lavia. Careful attention should also be given to the 

 watering of the plants. An excess of moisture in the 

 soil favors the disease. It is doubtful that spraying 

 will have any effect in controlling this trouble. 



Anthracnose 



Caused by Glceosporium viol(Z B. and Br. 



This disease attacks the edges of the leaves, start- 



♦Reddick, D. Trans. Mass. Hort. Soc: 85-102, 191 3. 



