Pest and Disease Control for Roses

by Don Trotter

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Hello Fellow Earthlings and welcome to the second of our five part series on rose care. This discussion will be focusing on pest and disease control. Let's get a look at those roses.

It is widely known that roses can be a real pain if they want to be or are in any way not attended to. This is not so of a rose that is allowed to grow under natural condition without nitrogen fortified chemical fertilizers and harmful insecticides and fungicides. The truth of the matter is that roses can be very easy to tend to if they are cared for with a light hand during the growing season. The fewer things that a gardener does to shock a natural balance of things the fewer problems will arise as a result of that shock.

Natural Pest Control for Roses by Using BT and Neem Oil

Chemical insecticides are only effective until the target pest develops a resistance to that chemical. Then it becomes necessary to alternate harmful substances to control an insect population that continually gets worse because of lack of competition and natural predators due to high concentrations of chemicals. The major rose pests that we encounter here in your rose garden can be controlled by establishing populations of two beneficial insects and periodic treatments with a bacterium and a tree sap extract. The two beneficial insects are the Green Lacewing and Trichogramma Wasps. These two insects will guard your roses against everything from Aphids to some Scales and Spider Mites. Lacewings are very active and voracious feeders whose host or target prey are aphids, mealybugs, whiteflies of some species, juvenile scale insects, and some spider mites. The tiny Trichogramma wasp is a parasite of caterpillars some species of budworm and will antagonize a number of other butterfly and moth species. These parasites do not have a stinger (no need to fear them), they have an ovipositor that lays her eggs inside the host. As the wasp larvae develop they use the host as a food supply.

The bacteria that I spoke of are Bacillus thuringiensis, variety Kurstaki or Berliner. This product is often referred to as BT and is a paralyzing bacterium that affects many species of worm and caterpillar including the leaf skeletonizer worm. By paralyzing the stomach of its host this bacteria is very useful against its target pests.

The tree sap that I was referring to is Oil of the Neem Tree of India. The active substance in this sap (seed oil) has been named Azidirachtin after the botanical name of the tree. The extracted oils from the tissue and sap of this tree are very effective at repelling and keeping your rose bushes free of any sign of insects. Although it smells like hazelnuts to us it has the most repellent affect on pest insects. Neem oil is sold under the name Bio-Neem under the Safer label and Rose Defense under the Green Light label. These two products can be found at any garden supply store. The very best Neem oil product I have ever used is manufactured by a Dr. Robert Green at 760-598-6050. It is a super concentrated material and it really keeps the pest insects at bay as well as function to keep disease pathogens from getting too prolific. Just ask Dr. Green for the same Neem soap Don Trotter uses, and he'll mail it anywhere in the country.

Control Infections in Roses with Balanced Soil

Controlling diseases in your rose garden is really not very difficult at all. There is no need for harmful fungicides that can cause severe physical problems or have a negative affect on outdoor pets and bees as well as wipe out entire earthworm populations from a single spraying. Balanced nutrition and a couple of minerals can keep your garden disease free without weekly exposure to chemicals.

Most diseases of plants will leave a healthy plant alone. It is the same with us, if we're healthy we don't get sick. Plants also have immune systems. This is where a balanced diet that contains the proper amount of copper, sulfur, potassium, magnesium and calcium will ensure that certain very commonplace and damaging fungi don't get a foothold in your garden.

Potassium is very important for resistance against powdery mildew and rust on roses. Not in some crazy amount that is available to the plant in five seconds after application but instead long lasting natural sources from mineral deposits or from other natural source. When potassium is broken down in the soil by a healthy soil it will actually help to prevent the onset and spreading of powdery mildew and rust, which are tough problems for most chemical gardeners to control. High calcium levels along with an abundance of naturally available magnesium will cause your roses to produce thick healthy canes without problems with of slow root development in our heavy soils. Copper and sulfur are the two elements, which I use as a spray fungicide if absolutely necessary. Other than dormant spraying minimal spraying should be necessary to prevent fungus and disease if the roses are fed naturally.

Got Questions? Email the Doc at
Check out Donald Trotter's books Natural Gardening A-Z, The Complete Natural Gardener and Rose Gardening A-Z at

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