If you have only a few minis, it is practical to get ‘ready-to-use’ (RTU) products in spray bottles. With larger plantings it's better to use a sprayer and mix your own spray.
Here is a new anti-fungal product that works for us
White, Black or Rusty Spots On Leaves Are From Fungal Diseases.
Black spot, powdery mildew, and rust are the three major disease problems of roses. While mildew is found nationwide, rust and black spot territories seldom overlap. Correct cultural practices can prevent many disease problems on roses. Plant rose bushes so that there will be a chance for air circulation around each plant to help minimize foliage disease problems. Water before noon; do not let water spatter on to the leaves to prevent fungus.
In all three cases the treatment is about the same. As a preventive step, spray vulnerable roses with garden sulfur fungicide as directed on the label during their dormant period in early spring. Check their growing tips and young leaves for signs of fungal disease when temperatures hit the mid 60's and rainfall is sparse. If it appears, prune off the infected parts and begin treatment. Spray healthy leaves and buds with the sulfur fungicide to prevent the spread of the fungus. Continue to remove all the leaves showing disease right away, and prune all branches as soon as a canker is spotted. Strip all leaves from the bushes after the first hard frost, to prevent rust or black spot spores from wintering over from year to year. Anti-transpirant spray products sprayed on healthy foliage show some promise of controlling fungal disease as well. Buy disease resistant bush roses.
Powdery Mildew: It is usually severe only in coastal areas with moderate temperatures, high cloud cover or fog and with minimal rainfall in the summer, such as in the Pacific Coast area. This is a white or gray powdery coating that appears on rose leaves, buds and canes. The disease starts on the young leaves as raised blister like areas that cause leaves to curl, exposing the lower surfaces. Infected leaves soon become covered with a grayish-white powder fungus growth. Unopened flower buds may be white with mildew and may not open. Mildew prefers young, succulent growth. The mature tissue on the plant is usually not affected. Powdery mildew usually occurs in periods of cool nights, humid days and no rain.
Rust: Rose rust is mostly confined to western United States. Small orange or yellow pustules (raised spots) appearing on any green portion of a rose bush indicates the presence of rust. Early infections usually occur on the undersides of the leaves and may be inconspicuous. Later, pustules develop on the upper leaf surfaces and stems and are quite visible throughout the summer. Some bushes will (drop)the infected leaves. It occurs during periods of morning dew.
Black spot: Black spot thrives in moist environments, being most common in the Northeast, Southeast, and in some Mid-western states with warm, moist summer climates. Dark black spots with a surrounding yellow area form on the leaves. The leaves turn yellow-pink and fall off. The young leaves 6 to 14 days old are most susceptible. In severe cases rose bushes can be defoliated by mid-summer. Black spot prefers rose bushes that produce light colored blooms, such as yellow. Red roses are not as susceptible. Black spot begins to appear when the air temperature approaches the mid 60's with abundant rain or high humidity. The spots first appear on the leaves, especially young ones, down low to the ground.
Leaves Are Curled and Distorted From Aphids.
Aphids are soft-bodied, pear-shaped sucking insects, about the size of the head of a pin. They appear on garden roses in May and June and are common in greenhouses. Most of them are greenish, but pink or reddish broods are often present on roses, especially early in the season. They multiply so rapidly that infested flower buds and stalks become covered with them. They are usually found feeding on the undersides of the leaves. They retard or distort plant growth. Leaves on roses may turn yellow or brown, wilt under bright sunlight, or sometimes curl and pucker. Sometimes a sticky secretion can be seen on the tops of leaves that attract ants. Flowers can become malformed.
For light infestations, spray the undersides of the rose leaves vigorously with water three times, once every other day in the early morning to dislodge the pests. f they persist, spray visible aphids with insecticidal soap according to label instructions. Spray affected foliage and buds with a pyrethrin/pyrethrum insecticide product for longer effectiveness. Do this in the late afternoon or evening to minimize its impact on beneficial insects and bees.
For more information see the file on Controlling Aphids
Leaves Discolored and Deformed From Mite Damage
Mites are about 1/50 inch long, about the size of a grain of pepper. They may be yellow, green, red or brown and are always found on the undersides of the leaves. Two-spotted spider mites and the red spider mite stipple and discolor leaves. They spin webs across leaf surfaces and on new growth. As the infestation proceeds, leaves become spotted red, yellow or brown, curl, and (drop)off. Some floribunda roses are so susceptible to mites that they lose their leaves prematurely.
Serious mite infestations can be caused by using certain chemical fungicides sold to control rose fungal diseases. Start control measures as soon as you notice the first stippling on the leaves. Spray infested bushes in the early morning with a forceful water spray to knock mites from leaf undersides. Repeat the water spray daily for three days. If that doesn't do the job, spray the mites with insecticidal soap according to label instructions.
For more information see the file on Controlling Mites
