Husker Hort

A Nebraska View of Horticulture

Enjoy Roses: flowers, thorns, bugs and all

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No doubts about it, roses were hit hard this winter. Whether you had hybrid tea roses or the tough-as-nails shrub roses, they all took a beating. Don’t let your roses suffer any more damage this summer, be on the lookout now and catch these common rose problems.

Japanese Beetles

Japanese Beetles

Japanese beetles are a common pest of roses. They will feed on most anything, but they have a love for roses. These insects are related to the May/June beetle and can be a major pest of roses. The immature form of the beetle is a grub that can do some damage to turfgrass. The adults hungrily devour roses and cause the most feeding damage. The front of this beetle is a dark metallic green and the wing covers are a dark tan or coppery color. The main identifying characteristics for these beetles are five small tufts of white hair along each side of the insect. They feed in clusters during the day on leaves or on the blooms. Adult Japanese beetles can cause the leaves to have a skeletonized appearance, ragged holes, or in some instances, the leaves are completely eaten.

Rose Chafers

Rose Chafers

Rose chafers are another beetle pest of roses. The adult beetles are slender, 1/2 inch long, and are light tan colored. They lack the tufts of hair that the Japanese beetles have. The long burnt-orange legs are the distinguishing characteristic that sets them apart, as they clumsily walk around. The adults feed on the foliage and flowers of roses, while the larvae feed on roots of grasses and alfalfa. Adults may feed together and can cause skeletonized leaves or ragged holes in the flowers.        

There are a few ways that you can control Japanese beetles and rose chafers on roses. If the infestation is light, hand picking is an option. Pick the beetles off in the early morning and drop them in a bucket of soapy water. There are also some deterrents that can be used like neem oil. Several insecticides are labeled for control of these pests with active ingredients like carbaryl, acephate, and chlorpyrifos. Keep in mind that these beetles are mobile and often new beetles take the place of those killed by insecticides. Try to avoid applying the products to the flowers or during times when bees are present because they can harm honeybees.

Black Spot on Roses- photo courtesy IANR Pubs http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=674

Black Spot on Roses- photo courtesy IANR Pubs http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=674

Some disease names lack imagination. Black spot of roses is one of those. This fungal disease causes the rose leaves to turn yellow then develop black spots, hence the name black spot of roses. The leaves that are affected might fall off, which can affect the appearance of the shrub. It can also reduce plant vigor, cause stunted growth, and increase the chance of winter kill. The fungal spores overwinter on fallen leaves and diseased canes. Rain splash or sprinkler impact easily spreads the spores onto healthy new plant material.    

Prevention is the best method for dealing with black spot. Following good sanitation practices like cleaning up rose beds in the fall will make sure to get rid of any old plant debris that could overwinter spores. Replacing old mulch with new, if black spot was a problem in the past in that location, as well as looking for and selecting rose varieties that are resistant to black spot will help to reduce or eliminate the need for a spray program.

Fungicides are another option for black spot control. For best results, most fungicide applications should be applied preventatively to healthy foliage to keep the leaves from becoming infected. Throughout the growing season, infected leaves should be removed as soon as symptoms begin to appear. On plants with a history of black spot, fungicides can begin to be applied as soon as the foliage begins to emerge in the spring and continued throughout the summer. Read and follow label instructions for application and reapplication recommendations. For best results, a fungicide should be used in combination with good cultural and sanitation practices.

With a keen eye, you can catch these issues before they become a pest in your rose bed.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.

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Author: Elizabeth Killinger

A Nebraska Extension Educator out of Hall County with a focus in horticulture and sustainable landscapes.

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