Client Request:  Could you help us with identifying the problem with our rose bushes. I used Bayer all in One Rose & Flower Care this Spring but it didn't do much good. What should we do? Thank You. 

MGCC Help Desk Response:  Thank you for contacting the Help Desk of the UC Master Gardener Program of Contra Costa County. Based on the photo you provided, it is likely that your rose are infected by Powdery mildew (Podosphaera pannosa). This fairly common fungi produces mycelia and spores on leaves and shoots, and sometimes on flowers. It looks like a gray (older infections) or white (newer infections) powder on both sides of the leaves, differentiating from Downy mildew, which tends to appear only on the underside of the leaves.

Powdery mildews spread with windblown spores. They do not need water to germinate and die when wet for an extended period. They like moderate daytime temperatures (60-80 degrees F), cold nights and shady and low light conditions. UC Agriculture and Natural Resources (UCANR) recommends a number of measures to control infestations but once a plant has extensive infections it is usually too late to control and prevent damage to the plant. It is hard to determine from the photo how badly infected your rose is, but the following recommended measures may be helpful in managing it.

1. Prune during the dormant season to increase air circulation and light penetration. Trim or remove adjacent plants to avoid crowding.
2. Remove infected plant parts to reduce spore production. This should be done when the plant is wet and the spores can't generate.
3. Irrigate using an overhead sprinkler in the morning when the spores would otherwise be released.
4. Some infections may require fungicides, these usually only prevent new infections and may need to be applied repeatedly when conditions favor disease development. Use less toxic pesticide products wherever possible and carefully follow instructions on proper use, storage and disposal to reduce adverse impacts to other species and the environment. Mild to moderate infections can be treated with horticultural oil or plant-based oils, such as neem oil. Do not apply in bright sunshine or when outside temperatures are 90 degrees or more as it may burn or otherwise damage the plant and some beneficial insects. Also, read instructions carefully on preventing harm to bees.
5. Disease prevention can also be effective with the application of sulfur products, especially ready-to-use soap like surfactants. These are not effective once the disease has appeared.

If your plant is substantially infected, consider removing it and growing a more resistant cultivar and species. Some examples are Meidiland shrub roses, Rosa rugosa, glossy-leafed hybrid teas, grandifloras, that are trademarked as Care-free, Knock Out, and Home Run. Plant in a sunny location and provide ample adjacent open space for air circulation. 

For additional information please see this link to UCANR Integrated Pest Management Program Pest Notes: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7463.html

We hope this information is useful.  Feel free to contact us again if you have any further questions.

Help Desk of the UC Master Gardener Program of Contra Costa County (NHP)

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Note:  UC Master Gardeners Program of Contra Costa's Help Desk is available almost year-round to answer your gardening questions.  Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone:  (925) 608-6683, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Biog.

 

Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Gardener's Help Desk Request: What should I use to seal rose canes after pruning? Is a dot of Elmer's Glue OK, or is something else more effective?
 

Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your questions about sealing the pruning cuts of your rose bushes.
 
There is no need to seal the pruning cuts of your roses with Elmer's Glue, or any other product. Rose canes will seal themselves, especially if pruned during their dormant season, roughly mid-December to mid-February at a 45 degree angle. If you have added any sealant, you would be better off re-pruning those canes.

Here is a link to a UC Master Gardener guide to rose pruning, including a chart about “Rose Care by the Month”, that you might find helpful. http://ucanr.edu/sites/mgslo/files/272360.pdf

Please do not hesitate to contact us again if you have more questions. And here's to a great rose year in Contra Costa County.

Help Desk of the UC Master Gardener Program of Contra Costa County (JJM)

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 Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone:  (925)646-6586, 

 

 

 

 

Home Gardening Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request: I have several roses in my garden that seem to bloom forever and well into late Fall/Winter. I'm confused on when to prune them compared to others that stopped blooming a month ago or so and are already going dormant. Would you provide me some guidance on when to prune these late blooming roses?

MGCC' Help Desk Response:  Thank you for contacting the UC master Gardener Program Help Desk with your questions about pruning your roses that are acting like it is springtime in November!

As we discussed earlier today on the phone, in our mild climate, it is not unusual for some roses to bloom well into November and even December, so you should not prune those roses until later in winter. UC's article on rose care says that in most of California, pruning should be done in winter before buds swell, although it may be delayed where late spring frosts are common. So, as discussed, enjoy your roses until they go dormant within the next couple of months and then prune!

Here is the link to the full UC article on rose care:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7465.html

Also, Sunset magazine says that repeat-blooming roses are usually pruned just before dormancy ends in late winter or early spring. Roses that bloom only once a season are traditionally pruned just after the bloom period ends; strong new growth produced after bloom will bear flowers the following spring.

If you have additional questions, please let us know!

Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/). 

Help for the Home Gardener from the Contra Costa Master Gardener Help Desk

Client's Questions and Problems:
Client lives in a condominium/town house complex in central Contra Costa County that permits individual gardens. The client grows both roses and grapes. Immediately adjacent, the Homeowners Association (HOA) maintains a privacy/sound wall covered in ivy (maybe English or Boston ivy). Client brought samples of the plants into the CCMG Help Desk for assistance identifying the plants' problems and what could be done about correcting them. All the plants look distressed with maybe a fungus or possible insect activity, the roses looking somewhat the same and also with black spots on the leaves, and the grape showing signs of distress including discolored leaves and withering. Several days after the client brought samples of the plant problems, and before CCMG could analyze plants for the problems, the client contacted the CCMG Help Desk again to inform HD that after reading an article in California Agriculture (2014, Jan-June, volume 68, page 20), it appeared that the grape leaves may be infected with Pierce's Disease (PD). Based upon the article, the client was concerned that all the grape vines should be removed. 

 

   

Pierce's disease is caused by a strain of the bacteria Xylella fastidiosa, which blocks the water-conducting system of a grapevine, leading to vine death 1 to 5 years after the plant becomes diseased. (Photos from California Agriculture, 2014, Jan-June, Volume 68, page 20)

 

 

 

CCMG Help Desk Response:
This is a follow-up to your recent discussion with our MG volunteer, and a follow-up voicemail regarding the discoloration and die-back of your grape leaves and roses. 

I. Grapes
You are correct that it looks like your grapes have contracted Pierces' Disease. The photographs you viewed on line and the photos we have viewed in our library certainly seem to confirm the presence of the disease. 

I don't know how many grape vines you have, but in case you have more than the one infected plant, here are some of the symptoms to look for: 

Symptoms
According to our Pest Management resources: 

“In vines that are infected in spring, symptoms of Pierce's disease first appear as water stress in midsummer, caused by blockage of the water-conducting system by the bacteria. The occurrence of the following four symptoms in mid- to late summer indicates the presence of Pierce's disease: (1) leaves become slightly yellow or red along margins in white and red varieties, respectively, and eventually leaf margins dry or die in concentric zones; (2) fruit clusters shrivel or raisin; (3) dried leaves fall leaving the petiole (leaf stem) attached to the cane; and (4) wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark. Delayed and stunted shoot growth occurs in spring following infection even in vines that did not have obvious symptoms the preceding year.  

Leaf symptoms vary among grape varieties. Pinot Noir and Cabernet Sauvignon have highly regular zones of progressive marginal discoloration and drying on blades. In Thompson Seedless, Sylvaner, and Chenin Blanc, the discoloration and scorching may occur in sectors of the leaf rather than along the margins.  

Usually only one or two canes will show Pierce's disease symptoms late in the first season of infection, and these may be difficult to notice. Symptoms gradually spread along the cane from the point of infection out towards the end and more slowly towards the base. By mid-season some or all fruit clusters on the infected cane of susceptible varieties may wilt and dry. Tips of canes may die back; roots may also die back. Vines of susceptible varieties deteriorate rapidly after appearance of symptoms. Shoot growth of infected plants becomes progressively weaker as symptoms become more pronounced.  

Climatic differences between regions can affect the timing and severity of symptoms, but not the type of symptoms. Hot climates accelerate symptoms because moisture stress is more severe even with adequate soil moisture.  

A year after the vines are infected some canes or spurs may fail to bud out, and shoot growth is stunted. New leaves become chlorotic (yellow) between leaf veins, and scorching appears on older leaves. From late April through summer infected vines may grow at a normal rate, but the total new growth is less than that of healthy vines. In late summer leaf burning symptoms reappear.” 

Outlook

Unfortunately, Pierce's disease is a lethal disease of grapevines. It is spread by certain kinds of leafhoppers known as sharpshooters. In our area, the blue-green sharpshooter is the likely culprit (also known as the “vector”) with the potential of the grassy-winged sharpshooter, an even more potent pest.

Management and Control
Control of sharpshooters is not effective, although removal of alternate hosts might help. Some alternate hosts are Bermuda grass, blackberry, and willow. There are many hosts though, so removal of these might not be effective either.

Removing diseased vines as soon as possible when Pierce's disease first appears is critical to help reduce infection of other vines.  I would not recommend putting them into your own personal compost bin. If there is a large volume, you might want to consider burning it. 

Remove the grapevines as they become unproductive. You could replant with less susceptible cultivars such as 'Sylvaner', 'Thompson Seedless', and 'Ruby Cabernet'. 

Certain plants have been identified as preferred breeding hosts for the blue-green sharpshooter (places they will lay eggs). These plants should be avoided if possible.

Blue-green Sharpshooter Breeding Plants
Blackberry	Fuchsia
Eldeberry	Periwinkle
Ivy	Geranium
Virginia Creeper	Liquidamber
Roses

As you can see, roses are one of the preferred breeding plants. Although Pierce's Disease doesn't infect roses, it is quite possible given that the sharpshooter prefers roses, and you mentioned that your rose is close to your grapes, that the plant is showing the effects from sharpshooter feeding. 

Currently, the only other recommendations with respect to plant selection are to plant conifers, or to establish a non-irrigated xeriphytic (i.e., dry) landscape. These plants should not be attractive to blue-green sharpshooters. 

Further information on identifying Pierce's Disease can be found at http://www.ipm.ucdavis.edu/PMG/C302/mt302sppiercedis.html

II. ROSES
From the sample you gave us, and a search of other photos we have, it appears that your rose might be suffering from a couple of things – black spot and the effects of the sharpshooters. 

Black Spot Symptoms
According to our resources, “Black spot causes black spots to develop on the upper surface of leaves and succulent stems. The spots have feathery or fiber like margins and no powdery growth on the undersides of leaves. Small black fruiting bodies are often present in spots on upper sides of leaves. Yellow areas develop around the spots. Leaves may drop.”

   

Yellow areas develop around spots

Solutions
The black spot fungus requires free water to reproduce and grow, so leaves should never be allowed to remain wet for more than 7 hours. (When hosing off aphids, do so in the morning so leaves have a chance to dry by midday.) Provide good air circulation around bushes. Remove fallen leaves and other infected material and prune out infected stems during the dormant season. Black spot is usually not a problem during California's dry summers unless overhead sprinklers are used, but the disease can be serious where rainy summers prevail or in cooler areas. Miniature roses are more susceptible than other types, although a few varieties are reliably resistant to all strains of black spot. A combination of bicarbonate of soda plus light horticultural oil can be used to manage black spot (as well as powdery mildew). Use about 4 teaspoons of baking soda per gallon of water with a 1% solution of narrow-range oil. Avoid getting on open blossoms. Neem oil can also be effective. Preventive sprays of fungicides such as triforine or chlorothalonil may also be effective. 

A UC IPM Pest Note (free), that will give you some more information on rose pest management can be found on the web at http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7463.html 

I hope this helps. Thank you again for bringing this problem to us. It was a lot of fun to research.

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Follow-up:  Further Questions and CCMG Help Desk Response:

From the Client: 
Thanks for all the helpful information. I see that I'll have my work cut out for me in taking out all the vines, cutting back the roses, and trying not to spread this further. I'll let my HOA know also, because I believe there is an extensive outbreak of something that has affected most of the ivy in the HOA's 30 acres. The ivy within a foot of my grape vines has all died off—and within 10 feet is a Liquidamber tree, and of course geraniums – all of the plants you listed as being breeding plants for the insects. My last question is should I be notifying the county ag department or vector control about this infection?

Follow-up Response:  from CCMG Help Desk:
We did some checking and Pierce's disease is not a reportable problem in Contra Costa County, so you don't need to notify anyone. 

We also don't think your HOA's ivy dieback is caused by PD, even though ivy is considered a host plant. There are also other insects and diseases that affect ivy, as well as cultural problems. I've been seeing many patches of ivy in the area that appear sunburned and water-stressed and even many drought-adapted plants are having serious problems this year. Here is information from UC that covers pest and diseases in ivy: http://www.ucdavis.edu/PMG/GARDEN/PLANTS/ivy.html. This may help your HOA trouble shoot the ivy problem.

Please feel free to call again if you have more questions.

Contra Costa Master Gardeners' Help Desk

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Editor's Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523.

We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, and we are on the web at http://ccmg.ucanr.edu/