Pasquesi: Garden Care - Roses (Coping with Common Rose Pests and Diseases)

COPING WITH COMMON ROSE PESTS AND DISEASES

Roses are susceptible to a wide variety of insect attacks and diseases that can rapidly destroy a beautiful garden. To keep plants healthy it is essential to follow a regular pest control program.

Consistent effort and some basic rules will ensure pests and diseases are kept at bay.

Guidelines

Spray or dust with fungicide every seven to 10 days throughout the growing season
Dust in the evening, or when wind is absent
Spray both the upper and lower surfaces of leaves with a fine mist
Apply pesticides early in the day to prevent the foliage from burning in high temperatures
Follow manufacturer's instructions

Preventing Disease and Insects

Proper site selection will encourage healthy roses. Roses need adequate air circulation and direct sunlight to discourage fungal infection.

Fungal spores need a film of water to germinate. When watering plants try to keep the foliage as dry as possible by concentrating the water stream near the base of the plant.

Ensure roses are planted in an area that receives at least six hours of full sun. This will help the leaves to dry should they become wet from rainfall.

Air movement will dry the leaves quickly as well. Place plants at least three feet from walls or fencing to allow the air to circulate.

Pruning

Spring pruning is a rose's spring cleaning. Pruning during early spring helps to remove all dead and diseased wood. It also encourages air and light to penetrate.

Identifying and Treating Common Rose Diseases

PROBLEM	DISEASE	APPEARANCE	WHAT IT DOES	TREATMENT
Black spots on leaves.	Black Spot	Circular black spots with fringed edges on leaves. Initially may appear as yellowish spots.	Causes leaves to yellow. Lower leaves are affected first.	Remove leaves. Spray with a garden fungicide, such as Funginex, every seven to 10 days.
Purple-red spots on canes. Entire plant is dying.	Brown Canker	Fungal spots on canes that later turn brown may spread around the stem.	Fungus can cause entire plant to die once it encircles the stem.	Prune can below diseased area. Dip pruning tools in alcohol to prevent the fungus spreading.
Tumors appear on crown or bud union below the soil level.	Crown Gall	Rough, rounded tumors caused by soil bacteria.	Eventually kills entire plant.	Dig up and discard infected plants. Replace the soil surrounding infected plant.
Young canes are stunted and malformed.	Powdery Mildew	Fungal disease covering leaves, buds and stems with white powder spread by wind.	Leaves curl and turn purple.	Spray Benomyl or Funginex every seven to 10 days.
Underside of leaves have "blisters" or orange spots.	Rust	Orange-red blisters that turn black in fall.	Attacks new growth in spring. Is able to survive winter.	Collect and discard infected leaves in fall. Spray Benomyl or Funginex every seven to 10 days.
Stunted or malformed foliage and blooms.	Aphids	Small soft-bodied green, brown or red insect clustered under leaves and flower buds.	Suck plant juices from tender new grown and buds.	Spray with malathion or diazinon.
Foliage, flowers and stems are chewed.	Beetles (various species)	Small hard-bodied insects found all over the plant.	Eat foliage, stems and flowers.	Pick beetles off plants by hand. Spray plants with Sevin.
Mottled, yellow-spotted leaves.	Leaf-hoppers	Very small yellow-green, jumping insects usually hiding underneath leaves.	Suck plant juices.	Spray with Orthene or malathion.
Canes are hollow or appear to be rotting.	Pith-borers	Insect and larvae difficult to spot as they live inside the rose cane. Check canes for external damage.	Bore into cane and lay eggs. Larvae eat their way down through the cane.	Cut cane off below the infection. Or prune back to expose wood. Seal wounds and entry points with nail polish, glue or prune compound.
Foliage is weak and dark in appearance. Leaves drop prematurely. Canes have brown spotted appearance.	Scale	Small insect that look like brown or gray dots on canes and stems. Also appear as tiny "seashell" marks.	Suck juices from canes and stems.	Prune and discard infected stems. Spray with Orthene or malathion.
Mottled and weak leaves. Tiny white webs under leaves.	Spider mites	Tiny, green, red or yellow spiders on the underside of leaves.	Suck juices from leaves.	Apply Isotox or Orthene.
Flowers don't open or they open deformed. petals are flecked with brown.	Thrips	Slender, brown-yellow insects with fringed wings nesting in flower buds.	Suck juices from flower buds.	Cut and discard infested flowers. Apply malathion or Orthene in spring before buds have developed.

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