What are the black spots on my rose bushes?

Those unsightly and damaging black spots on your rose leaves, commonly called “blackspot”, are caused by a wind borne fungus also known as “Diplocarpon rosae”.   You will notice this fungus when your rose leafs have a black round spot, eventually turning the leaves yellow and causing them to fall off leaving you with an unsightly looking rose bush.  This disease can be devastating to rose bushes and if severe enough will weaken your bush and blooms.  

Blackspot is especially prevalent in climates with a lot of rain or high humidity.  Blackspot cannot be cured but there are methods to control the spread of this damaging disease.

One way is to remove the areas affect by black spot and be sure to pick up any leaves or other parts of the plant that still harbor the fungus or it will possibly spread from the fallen leaves.

Using fungicidal soap or Sulphur in dry weather (as rain will rinse these off) is one solution to help prevent further damage.  Both of these can be obtained at your local nursery.  There are also natural solutions that may help slow blackspot disease.  

According to horticultural professor Jeff Gillman, a spray composed of one part milk and two parts water will help when applied weekly.

The best prevention for black spot disease is to space out your roses when planting to allow air circulation.  It is also best to water your roses using a drip or soaker type hose on a day the sun will dry out any possible moisture on leaves.

Whats eating my rose bushes?

Its always hard when your an avid gardener with prize winning roses to go out one day and see holes in your leaves.  A lot of rose bushes around town usually get hit about this time with pesky vermin having your roses as its main course.  There are a number of insects that can be the culprit of the crime.

The most common are aphids, the are small to the naked eye and can be green, red, or brown. The feed on the new buds that are forming. They can usually be controlled by a strong blast of water from your garden hose, begins spraying from the bottom and working your way up making sure to get the underside of the leaves. If the aphids fall from the plant and into the soil, they for the most part don`t crawl back up. There are also good insecticides on the market to control them.

Rose slugs and thrips are the most common leaf eater found in the St. Louis area. They eat the rose leaves leaving small holes and small gray spots that look like scales.  Most of this damage isn`t severe enough to hurt the plant. A good watering daily will help the plant survive while the leaves are eaten. Try to treat early, if so desired, once the leaf damage becomes apparent. 

Most pests on any plant can be dislodged from the plant from a good hose blast, as stated earlier, and daily monitoring of the plant.