You can use dish detergent instead of insecticidal soap to treat aphids on roses (Rosa spp.). For homemade aphid sprays, use liquid dish soap meant for hand washing dishes, not detergents formulated for grease removal, citrus-based or scented soaps, nor dishwasher or laundry detergents, as these may harm rose bushes. Always test homemade spray on a small area of a rose bush and check for harm the next day before applying a soap you haven’t used before to an entire rose bush.
Aphids on Roses
All kinds of aphids like roses, including the main rose-attacking aphids, rose aphids. Aphids suck the sap out of the rose tissues and they excrete a sweet material, called honeydew, that attracts ants and ants protect aphids from some of their natural predators. The honeydew promotes black mold on roses bushes. Although a healthy rose bush can withstand a moderate number of aphids, they reproduce quickly and extensive infestations can cause substantial harm. In warm climates, aphids may reproduce year-round. Roses grow in U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on variety.
How Soap Sprays Work
Soap may kill aphids by removing the waxy protective layer that holds in their body moisture. While homemade sprays mean fewer unpleasant chemicals, you have to apply them more carefully. The aphids need to be covered by the spray for it to work. Regular dish soap doesn’t harm beneficial insects including bees and ladybugs. Ladybugs eat aphids and control their populations. Commercial insecticidal soaps are safer for plants than dish soap because they’ve been designed not to remove the plant’s waxy cuticle the way dish soaps might, notes horticulturist Jeff Gillman in his book “The Truth About Garden Remedies: What Works, What Doesn’t, and Why.” Rose bushes have a waxy surface that protects them from dehydration. If the rose leaves look dull after they are rinsed and dried, the soap may cause dehydration.
The Basic Recipe
The usual concentration of soap is about 2 percent, which is 5 tablespoons of soap in 1 gallon of water. For best results, plan to use your soap spray on the roses early in the morning or in the evening. This reduces dehydrating qualities of the solution and allows it the most time to work on the aphids. This same soap spray helps control other soft-bodied garden pests, including spider mites, psyllids and mealybugs.
Going in for the Attack
Put on a heavy, long-sleeved shirt and leather gloves to protect yourself from thorns. If you’ll be spraying rose bushes that are taller than you are, wear a hat use a step stool. If your spray bottle has an adjustable spray, set it for a wide spray, not a narrow stream. Although a narrow spray may knock some aphids off the plant, for the soap to work on them you need to wet them with it. On roses, aphids often congregate on buds and the undersides of leaves, so concentrate on those areas. Spray the aphids from within 12 inches, beginning from the lowest point where you see aphids and working your way up the rose bush. Apply the soap spray every five to seven days until the aphids are gone.
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