Roses are the world's favourite flower, and black spot is the scourge of rose growers. Black spot is a fungal disease and it thrives in warm humid climates. It starts off as a black spot in the leaf and then it turns yellow and eventually the leaf falls off, and if it's really bad, the plant can die.
When the black spot spore lands on the leaf, it germinates and sends its little root system through the cell wall into the sap stream below and it proliferates. If you thicken that cell wall, the spore lands on the top, the root system germinates and it goes halfway through and then fizzles out, and so you get less black spot. But how do you thicken that cell wall? It's easy - just use sulphate of potash and give them about 100 to 150 grams per bush about four times a year – this should guarantee a lot less black spot.
Nutrition and spraying will control most black spot but from time to time some bushes will be chronically affected. The only thing to do is to rip these out so they don’t infect any of the others.
No comments:
Post a Comment