Big, beautiful blossoms on roses (Rosa spp.) can be thwarted by voracious pests. Using commercial chemical sprays to douse the pests on the leaves and petals of healthy rose bushes can be harmful to children and pets. But there are a few ways to create an effective and inexpensive homemade insecticide to kill the bugs on rose bushes.
How to Apply Homemade Insecticide
While blasts of water are typically used to take down aphids and other pests seen on leaves and buds, all that water can cause powdery mildew to form on rose bushes. When spraying homemade insecticide for rose bushes, apply the spray in early morning or late in the afternoon when bees aren't present or foraging for pollen.
Make sure to cover the infected area to coat the pests you can see. Spray the top and underside of the rose bushes' leaves as well as the shoots, buds and blooms.
To prevent pests from popping out early, spray the rose bushes with homemade insecticide as soon as spring temperatures reach 50 degrees Fahrenheit.
Using Oils to Eradicate Pests
Oils are often the base of homemade insecticides for rose bushes. Soft-bodied insects, such as aphids and mites, are beaten back quickly with a spray that contains cottonseed, vegetable, mineral, neem or jojoba oil.
Oils are ideal because they don't leave any toxic residue and are relatively safe for beneficial insects, such as honeybees. They can also staunch the spread of diseases to which roses are susceptible, including powdery mildew.
The oil kills soft-bodied insects by suffocating them and penetrates into the pests' eggs to kill off future infestations. Some oils, such as neem oil, also repel other insects from setting up a colony. Cornell University has a formula for removing pests that combines one teaspoon each of horticultural oil, baking soda, and insecticidal soap mixed in a quart of water.
Vinegar to Prevent Pests
The household astringent is a safe and effective rose spray ingredient when used in small amounts. Vinegar can possibly damage the rose bushes' leaves or buds, so don't apply too much to the plant. The mix has a small amount of vinegar paired with other ingredients. Use a light hand so that the oily mixture covers the target pests but doesn't clump in the creases of the petals or the base of buds and damage the potential blossoms.
Start with a concentrated base of 1 cup of water and a tablespoon of vinegar. To this, add 1 1/2 tablespoons of baking soda and 1 tablespoon of liquid dish soap. The mixture may fizz, which is normal. Top this concentrated base with a tablespoon of neutral cooking oil, such as vegetable oil. Pour the entire mix into a gallon of water and stir until it is well combined. Spray it on the rose bushes immediately.
Homemade Insecticide With Natural Ingredients
Dusting rose bushes with flour kills the aphids and other soft-bodied pests. The pests eat the flour and become constipated and die off. A teaspoon of mild dishwashing liquid and a quart of water with a pinch of cayenne can also be used to suffocate the mature bugs. Spray it on the plants every other day or so for two weeks to kill off new pests as they hatch.
Kimberley McGee is an award-winning journalist with 20+ years of experience writing for a variety of clients, including The New York Times, Las Vegas Review-Journal Home section and other national publications. As a professional writer she has researched, interviewed sources and written about home improvement, interior design and related business trends. She earned a B.A. in Journalism from the University of Nevada, Las Vegas. Her full bio and clips can be viewed at www.vegaswriter.com.