Pests and Diseases Affecting Roses
In the British Isles there are few rose pests, and they are relatively easy to control. Aphids and thrips or thunder flies are the chief offenders. They are mainly active during warm, sunny spells, especially in late spring and early sum-mer. Caterpillars and leaf hoppers may also be troublesome, although attacks rarely assume epidemic proportions. Tackle all pests by spraying promptly with a suitable insecticide.
Black spot occurs mainly in country gardens, as the fungus thrives in pure air. No variety is immune, although some are resistant. Spray with a captan fungicide, to anticipate reinfection. Mildew occurs at times in practically every garden, particularly in dry seasons after sudden temperature changes, but varieties with glossy leaves often tend to be fairly resistant. Preventive spraying is again essential to control the disease. Use a Karathane fungicide. Rust is restricted mainly to south-west England, the Midlands and Northern Ireland. Frequent preventive spraying with a thiram fungicide is imperative since this is the most difficult of all rose disorders to keep in check.