Spraying  

If I could find varieties of modern roses that never contracted diseases or attracted bugs, I'd happily omit this chapter.  If there were no such thing as mildew to turn leaves white or rust to color them orange or hosts of other garden gourmets waiting to devour your succulent bushes, I'd skip ahead to the more alluring sections on cutting and exhibiting.

But I can't skip this chapter, and you can't skip spraying.

The perfect climate or terrain for growing roses doesn't exist.  Every spot has soil, temperature, moisture, or vegetation that will encourage some of the many rose scourges to wreak havoc on your garden if you don't get there first.

Fungus Diseases

These head the list.  The big three of these depressing afflictions are mildew, rust, and blackspot.  How severe they are will depend on where you live.  For instance, I've never (knock on wood) had blackspot in San Francisco or Petaluma, but I've sure dealt with my share of mildew and rust.

Mildew is the worst of the fungi for me, and it probably will be for you; it seems to transcend locale.  Classically, it's caused by warm days and cool nights, but less obvious weather extremes can produce it also.  Mildew thrives on overcrowded plantings and in damp shady gardens where air circulation is poor.

Crinkling leaves with no color changes are the first sign of mildew.  Then small round patches of mold appear and later become powdery areas of fungus filaments that harbor spores.  Mildew appears on foliage, stems, thorns, or on everything.

Rust, well described by its name, appears on the undersides of leaves as reddish orange pustules that look like warts.  Left un-checked, rust will work its way to leaf topsides and eventually defoliate the entire bush.  Moist conditions such as winter rains, summer fogs, and heavy dew bring on rust.  Supposedly, leaf surfaces must remain wet for four hours for spores to germinate.

Rust disappears during hot summer spells since spores can't survive temperatures in excess of 80 degrees for longer than a week.  Insects, wind, and rain spread the disease spores, most rapidly when fallen leaves are allowed to dampen.

Blackspot occurs mostly in humid weather and in areas of abundant summer rainfall.  Blackspot affects both sides of leaves with black rings that may be surrounded by yellow fringes.  As the fungus develops, leaves may lose all their green and turn yellow.  Rain or watering will accelerate its spreading, and its spores live through winters if they remain in cane lesions or on fallen leaves.