Tips For Handling Rose Pests And Diseases Organically

When roses are attacked by pests or disease, it is not necessary to use poisonous chemicals to solve the problem. There are organic alternatives.

Unfortunately, even with the best care, roses, not unlike other plants, can have problems with pests and diseases. But before you race for a poisonous cocktail that you have to spray while wearing protective clothing, take the time to identify exactly what is bugging your roses and quickly employ some effective organic controls

There are a number of different pests known to wreak havoc on roses, but it's not necessary to spray them with toxic chemicals that are as dangerous to humans as they are to the pests. Consider organic alternatives for the following pests:

Aphids

Aphids are soft-bodied green, red, pink, brown, or black sucking insects about 1/8 inch long. They are commonly found in early spring on soft new growth, where they cluster on the tips of young leaves, stems, flower buds, and blooms. Their feeding dwarfs and disfigures foliage and flowers. To control aphids, employ preventative measures such as applying dormant oil in late winter or early spring to destroy eggs. Use less nitrogen fertilizer, and introduce lady beetles, which prey on aphids yet do not harm rose plants. If, despite your preventative measures, aphids appear, wash them off plants with strong sprays of water or insecticidal soap. Heavily infested sections should be pruned and destroyed.

Beetles

Beetles are chewing insects with hard wings that eat rose leaves and flowers. Their grub-like larvae feed on the roots. You can treat your lawn with milky disease to destroy beetle larvae in the soil, but this can take a few years to have much of an impact on the population. In the meantime, you can place traps about 50 feet downwind from your garden to destroy adult beetles or try the age old tradition of picking them off by hand in the early morning when they are inactive. Simply drop them into a can of soapy water to finish them off. You may also want to spray infected plants with a mixture of 1 tablespoon isopropyl alcohol to a pint of pyrethrin mixture every 3 to 5 days.

Bristly Rose Slugs

Bristly rose slugs are the slug-like larvae of sawfly wasps. They are light green and up to ½ inch long. These pests feast on the undersides of rose foliage, turning leaves into mere skeletons. They are especially destructive in the early growing season. The best way to eradicate these pests is to spray foliage with an insecticidal soap, or hand-pick them while wearing gloves.

Cane Borers

There are various types of larvae that enter stems and canes from cut ends or by puncturing them, thus causing shoots to wilt, be stunted, or die back. Damage by cane borers is mostly cosmetic. The best way to prevent them is to paint pruning cuts with wood glue or shellac. If they have already invaded the plant, prune the canes below the infested part and destroy.

Caterpillars

Butterflies are beautiful, but their larvae are not. These wormlike creatures completely eat leaves or leave just skeletons of leaves behind. They also eat buds and flowers. The solution is to hand-pick caterpillars and destroy them and to spray weekly with BT until the caterpillars are gone.

Scale Insects

Scale insects have round or long and narrow white, gray, or brown hard shells about 1/8 inch wide. They suck sap from plants. Early signs of scale infestation are wilted and darkened leaves, then dropped leaves and stunted growth. If the infestation is severe, the canes become encrusted with scales. Light infestations can be treated with a cotton swab dipped in isopropyl alcohol. For heavier infestations, spray your plants every 3 days for 2 weeks with a mixture of 1 tablespoon isopropyl alcohol to a pint of insecticidal soap. Prune and destroy any thickly encrusted canes.

Spider Mites

The microscopic spider mite is a red, brown, yellow, or green sucking mite that causes leaves to be stippled with yellow, red, or gray; to curl up; and to fall off. Often webbing will appear on the underside of leaves. Spider mites are more prevalent during hot, dry weather. There are several ways to prevent spider mites. Clean up the garden well in fall or early spring because mites overwinter on weeds and garden trash. Destroy overwintering eggs by spraying plants with dormant oil in late winter. If the weather is hot and dry, wash foliage with water once or twice a week. If an infestation occurs, wash the foliage three days in a row; if it is heavy, spray foliage with insecticidal soap every three to five days for two weeks.



Thrips

Thrips are tiny yellow, black, or brown piercing-rasping insects that feed on flower buds, causing petal edges to brown or buds to remain closed. New plant growth may be deformed, damaged, or mottled. Thrips are worse during dry weather, and they are especially attracted to white and yellow roses. To detect them early, use yellow sticky traps four weeks after the last frost. If you find them, spray your plants with insecticidal soap every three days for two weeks.

You may have garden pests under control, but your rose plants may still be susceptible to a number of damaging, and even fatal, diseases. Should you find yourself dealing with some type of bacterial or fungal disease, keep the dangerous chemical sprays and dusts on the shelf. There are safe alternatives.

Blackspot

This is a fungal disease that forms black circles with yellow margins 1/16 to 1/2 inch in diameter. These circles may eventually blend to form blotches on leaves and canes. In severe cases, the entire leaf will become yellow and fall. Leaves less than two weeks old are most susceptible to blackspot, and it is most common in areas with hot, humid, summer climates. To prevent blackspot, plant disease-resistant cultivars. Avoid wetting the leaves when you water, and prune plants to improve air circulation. In the fall, gather and destroy leaves and pruned canes. At the first sign of damage, prune damaged foliage. If necessary, spray every 7 to 14 days with fungicidal soap or wettable sulfur.

Canker

Canker is a fungal disease that causes lesions or swollen, discolored areas on canes. In severe cases, it causes dieback from the tip. It enters the plant through pruning cuts and insect wounds. You can help prevent canker by painting pruning cuts with wood glue or shellac. If it appears, prune the canes below the infested part and destroy them. Dip your shears in disinfectant (such as isopropyl alcohol) between cuts.

Crown Gall

Crown gall happens when soil-borne bacteria enter the plant near the bud union or the roots and cause rough, swollen growths. A plant that has been infected with this bacteria will experience poor growth and flowering. To control crown gall, avoid wounding rose stems or roots. Check new plants for infection before buying, and remove and destroy infected parts on established plants. If the disease reappears, remove and destroy the entire plant. You should then select a different location for replanting.

Powdery Mildew

This fungal disease starts on young plants as raised blisters. Eventually, new growth and flower buds will be covered with a thin, white, powdery substance, and the growth will become deformed. Powdery mildew is found just about everywhere, but it is worse in areas where there is little rainfall. Prevent the disease by planting mildew-resistant cultivars. In the spring, start checking daily for signs of the disease. Prune infected parts immediately and spray the plants weekly with fungicidal soap or wettable sulfur. A mixture of baking soda and water works well too.

Rust

Rust appears as small orange spots on the underside of leaves and light yellow spots on the upper side. Long, narrow spots may also appear on young canes, and leaves may drop in the summer and fall. Optimum conditions for rust include temperatures between 640 and 700 F and continuous moisture for 2 to 4 hours. To treat rust, start checking foliage in early spring and cut diseased leaves. When the conditions are ideal for rust, spray roses weekly with fungicidal soap or wettable sulfur.

If you have chosen roses suitable for your location, selected a good site, planted them properly, and given them a reasonable amount of care, you should have very few problems with pests and diseases. For the occasional problem that does arise, know that you can safely treat your plants without danger to beneficial insects and very importantly, without danger to yourself.

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