Wednesday, January 30, 2013

Spring planting season ~ Roses and black spots

A Microscopic Fungus -- Black spots on roses appear mainly due to high humidity, and watering late in the day, which doesn't give the leaves a chance to dry. Although black spots can be transferred to roses for a number of reasons, via the air, the moist conditions are a perfect storm. Prevention is the best to deal with this.

Take advantage of the drying and disinfectant quality of sunlight by watering your rose bushes early in the day, and try to avoid wetting foliage. The fungi spores need at least seven hours of moisture before they germinate, so avoiding wetting the leaves is your first line of defense. Use a fungicide spray---trifloxystrobin, ziram and captan are a few of the chemicals available---and choose liquid solutions rather than dust for better control. To increase effectiveness, add a spreader to the fungicide. Protect plants by spraying regularly and by making sure that all leaf surfaces are exposed to the fungicide.

For an alternative, chemical-free fungicide, use Neem oil or two tablespoons of bicarbonate of soda diluted in a gallon of water. 

Prevent the spread of the fungus by pruning affected leaves and burning them. To avoid cross-contamination, clean scissors after every cut. Make sure the fungus doesn't overwinter by gathering any fallen leaves from around the plant and burning them as well.

A all natural recipe for Black Spot
1 tsp baking soda
1 Tbsp dormant oil
1/2 tsp dish soap
1 gal water

1. Mix all ingredients in a clean bowl or bucket, mix well. Pour desired amount in a spray bottle. In the morning or early part of day spray your rose bushes genereously. It is best to do this in the early part of spring to also prevent the early pests.

  • Give your rose bush plenty of sun. If something is obstructing the rose bush from receiving sun, such as an object or their location, take steps to remove that obstruction or move your rose bush. The black spot fungus is more likely to spread in dark, moist places, which sunlight helps eliminate.

  • Water only the roots of your rose bush. Do not get any unnecessary moisture on the stems, leaves or roses themselves. This will cause the black spot fungus to spread. Always water in the morning so the sun can help dry the rose bush quickly.

    Prune the rose bush as much as possible. The denser the bush is, the more likely the black spot fungus is to spread. Cut away any areas that are already infected with the fungus.

    Spray the leaves of your rose bush with wettable sulphur and a soap-containing fungicide, both available at plant nurseries. This will help prevent the black spot fungus from returning.

    Mix 3 tbsp. of natural apple cider vinegar into 1 gallon of water. Add 1 tbsp. of molasses and spray or pour this liquid onto the roses to rid them of the black spots.
    Use a sulfur spray. In most gardening circles, using sulfur is considered to be using an organic product since it is a naturally occurring element. Find a spray that contains sulfur as the main ingredient and spray it on your roses.

    Spray a milk mixture on your roses. Although it doesn't seem like a likely cure, milk can be used to treat the black spots on your roses. Combine a little milk with water and spray the milk on your roses to treat the roses with this chemical alternative.

    Blend cornmeal with some water until it forms a paste. Rub this on your roses. Let the paste stay on the flowers until it comes off naturally due to the weather and other elements. Cornmeal is a coating substance that can lift the black spots from the flowers.

    Use the "Cornell Formula." The formula was discovered at Cornell University and, like the cornmeal, is used to coat the leaves. Mix 1 gallon of water with 3 tsp. of baking soda and 1 tsp. of  canola oil. Coat the leaves until the mixture naturally dissolves.

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