If you are losing the battle with bugs and disease, try these environmentally friendly alternatives to pesticides. Many problems can be managed with cultural controls before they get out of hand (like pruning off infected leaves or physically removing pests), but sometimes you need more – especially during cool, wet weather.
Natural solutions require more frequent application to achieve control, but do not pose significant health risks like traditional chemicals. As an added benefit, they are generally inexpensive to prepare. Don’t forget to spray the underside of leaves as well as the upper surface during application.
Aphids, Mites, Scale & Whiteflies
Aphids reproduce rapidly and like tender new growth Aphids reproduce rapidly and like tender new growth
Spider Mites are found on the undersides of leaves and may cause stippling damage Spider Mites are found on the undersides of leaves and may cause stippling damage
Orange Oil Cleaner – Dilute 1 teaspoon per gallon of water. Use as needed by spraying on leaves. Good coverage is important: Wet leaf surfaces to the point of drip.
Soap Spray – Mix ½ teaspoon mild dish soap and 1 teaspoon cooking oil in a 1-quart sprayer filled with water. Spray liberally over entire plant.
Bring in Ladybugs – To keep aphids in check, release ladybugs on the affected plant. They will stay as long as there is shelter and host bugs to feed on.
Blast with Water – Aphids may also be dislodged by a strong jet of water.
Slugs & Snails
Beer – Pour an inch of beer into the bottom of an empty tuna or cat food can. Set it in the garden. Slugs and snails, attracted to the yeast in beer, crawl in and drown.
Handpick – Collect at night and remove from the garden area.
Coarse Sand, ¼”-minus Gravel, or Hazelnut Shells – Apply sand or gravel in trails around roses, or topdress beds with crushed hazelnut shells. Slugs and snails prefer not to cross abrasive surfaces.
Powdery Mildews, Blackspot & Rusts
Baking Soda Spray – Mix 1 tablespoon baking soda and 1 teaspoon cooking oil in 1 gallon of water. Place in spray bottle or tank sprayer and apply liberally. Repeat as needed.
Sanitation – Remove infected leaves and destroy. Do not compost. Keep the ground surrounding your roses free of leaf debris and weeds.
Cold Water – For Powdery Mildew, spray affected leaves with cold water early in the morning and allow leaves to dry in the sun.
Leaves fall when tapped = Too much water.
Leaves stay on when tapped = Too dry.
Crunchy leaves = Too dry and too late to save. Cut back as needed to promote regrowth.
Exceptions: Some rose leaves turn yellow in the fall. This is normal coloration.
Source : http://www.heirloomroses.com/