Master Gardener April 2005


Thursday, April 28, 2005


Dr. Vera Krischik

    Quiz 2: 2005 Rose galls
Quiz 2 Instructions
  From your readings on the websites below and other websites, please answer the following questions. Cut and paste or attach your answer into the email message and add "MG" and your name and quiz number to the top of the answer. Answers should be emailed to MGADVANCED@LISTS.UMN.EDU. All enclosures must be labeled "last name, quiz #.doc."
Quiz 2 Assignment
  Discuss in several paragraphs how to manage cynipid rose galls and how to differentiate between cynipid galls and buprestid damage. Do you think systemic imidacloprid will manage the wasps and borers?
Quiz 2 Online Resources

Mossy rose gall, Diplolepis rosea; Spiny rose gall, Diplolepis bicolor:

1. Insect pests of roses (Kevin Stroom, Jody Fetzer,  and Vera Krischik, U Minnsota Extension Service)

2. Insecticide Suggestions to Manage Landscape Tree and Shrub Insects (U of Minnesota Extension Service)

3. Roses for the North (Kathy Zuzek, Marcia Richards, Steve McNamara, and Harold Pellett, U Minnsota Extension Service)


Rose Stem Borer

The rose stem borer, Agrilus aurichalceus, damages rose canes when larvae tunnel in a spiral fashion beneath the bark, girdling and killing the canes (figures below). Their presence is indicated when a cane dies above the point of borer tunneling. Leaves on the infected cane turn brown as they die, creating a “flag” among healthy, green-leaved canes. On close observation, a swelling or gall on the infected cane can be seen below the dead tissue, indicating where the borer’s tunneling occurred. The gall formation weakens canes and it is common to see infected canes broken off by wind. The quickest and most effective control is removal and disposal of infected canes in fall.


Mossy Rose Gall

Mossy rose galls are caused by Diplolepis spinosa, a cynipid gall wasp. These galls are common on wild roses of North America, from Ontario to Alberta in Canada and throughout most of the northern United States. They are becoming common on Rugosa cultivars.17 The presence of these insects is indicated by the formation of spherical, golf ball-size, spiny galls on the canes of host plants.


The development of these galls is stimulated in the spring by newly hatched larvae. The galls encase the larvae until adult wasps emerge the following spring. The galls are unsightly and alter the plant’s shape. They also stress the host plant, behaving like nutrient sinks, drawing nutrients away from the rest of the plant. Large numbers of galls on a plant can kill the plant.


Insecticides have no effect on the wasp that causes mossy rose gall. The most effective control is physical removal and disposal of galls in autumn after leaves have dropped and galls are visible. It is important to dispose of all galls since even a single missed gall can produce and reintroduce 30 to 40 mature wasps to the garden the following spring.

Mossy rose galls caused by Diplolepis spinosa on rose canes. Hybrid Rugosas are particularly susceptible to this disfiguring gall.


New for 2004!


3 PRODUCTS IN ONE - insect protection, disease protection, fertilizer

New product from Bayer Advanced will revolutionize rose and flower care! No more bi-weekly spraying!


Bayer Advanced Garden™ All-in-One Rose & Flower Care's exclusive formula feeds and protects against insects and diseases in one easy step. It provides six weeks of protection against the major problems of Roses, Hibiscus, Iris and other flowers and shrubs. No spraying is necessary, just mix it in a bucket or watering can and pour this formula around the base of the plant. Root uptake starts the systemic process that distributes the product throughout the plant.


All-in-One Rose & Flower Care contains a Bayer proprietary fungicide (tebuconazole) and an insecticide (imidacloprid), plus a fertilizer (9-14-9) for strong roots and blooms! The product controls all major insects and diseases through systemic protection!

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Last Revised: April 28, 2005
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