Miniature Roses with Yellow Leaves

Spider Mites

• Spider mites damage rose leaves by feeding on their sap. Mites are tiny bugs that are hard to see, but they leave fine webbing on the leaves which, along with yellowing leaves, are symptoms of infestation. Look for mites by placing a piece of white paper under your plant and shaking the leaves over it. The mites will look like tiny moving dots on the paper. Control mites by spraying your plant with a strong spray of water several times a week. You can also immerse the top of your plant in a solution of soapy water, after wrapping plastic over the top of the pot to hold in the soil. Rinse with warm water.

Powdery Mildew

• Powdery mildew is a fungus infection that shows up as a dusty white or gray powdery coating over the surface of the leaves. Leaves can also turn yellow and die, or look distorted and stunted. Powdery mildew is worse when it’s humid out, or when plants are crowded together or grown in the shade. Control this fungus by cleaning up and destroying infected leaves, reducing humidity and spraying roses with a fungicide.

Blackspot

• The blackspot fungus causes black spots to appear on the upper surface of leaves. A yellow halo surrounds each spot, and the entire leaf can turn yellow as the spots grow and blend together. Purple and brown marks appear on canes. Prune infected canes, and remove and destroy diseased leaves. Fungicides can help prevent infections, but won’t cure infected plants. Avoid watering plants from overhead.

Anthracnose

• Anthracnose symptoms include the appearance of small red, brown or purple spots on the leaves. The center of the spots turn white, and may fall out of the leaf. As the disease progresses, the leaves turn yellow and fall from the bush. Apply fungicides to prevent infections, and avoid overhead watering.

Mosaic

• Rose mosaic virus causes the leaves to become streaked with yellow. Plants don’t grow as fast and flowering is reduced. Mild cases may clear up by themselves. Plants that are severely infected should be removed. There is no chemical cure.

Watering

• Yellowing leaves, especially bottom leaves, may indicate that your roses aren’t receiving enough water. Water indoor roses thoroughly, whenever the top inch of soil is dry, until the water runs out of the drainage holes in the bottom of the pot. Pour off excess water. Provide outdoor roses with 1 or 2 inches of water every week. Mulch to retain water and avoid overhead watering, if possible, to reduce possible fungal infections.

Nutritional Problems

• Yellow leaves, especially old leaves, spindly roses and lack of flowers can be a sign of nitrogen deficiency. If just the leaf edges turn yellow, it can indicate that your roses need magnesium sulfate. A deficiency of iron and zinc can make new leaves appear yellow between the veins. Nutritional deficiencies can be caused by growing your roses in the wrong type of soil. Roses prefer a pH of 6.0 to 6.5. Test your soil and amend the pH.

Herbicides

• Yellow, curled, small or cupped leaves can also be a sign of herbicide damage. The severity of damage depends on the type of herbicide and the amount your roses receive. Roses are often injured by exposure to glyphosate. If the herbicide is applied in the fall, roses may not show symptoms until spring. Roses may outgrow injury if the exposure was mild.