Happy Memorial Day Weekend, lawnkid. From your comments, I started thinking that maybe it is powdery mildew or a thrip infestation but then I noticed that I could not view your pictures. Can you make sure that you are sharing your album (i.e., the album is public)? Thanks, Luis

I could view your photos OK but couldn't see any powder. I did see leaves with white areas between green veins.

Yellowing of a leaf between dark green veins is called chlorosis and is usually caused by an iron deficiency. Many conditions can be responsible for an iron deficiency. Poor drainage, planting too deeply, heavy soil with poor aeration, insect or fungus damage in the root zone and lack of moisture all induce chlorosis. After these conditions are eliminated as possible causes, soil testing is in order. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency or magnesium deficiency. Iron is most readily available in acidic soils between pH 4.5-6.0. When the soil pH is above 6.5, iron may be present in adequate amounts, but is in an unusable form, due to an excessive amount of calcium carbonate. This can occur when plants are placed too close to cement foundations or walkways. Soil amendments that acidify the soil, such as iron sulfate or sulfur, are the best long term solution. Foliar sprays of iron sulfate or chelated iron can reduce symptoms. A combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Chlorosis caused by magnesium deficiency is initially the same as iron, but progresses to form reddish purple blotches and marginal leaf necrosis (browning of leaf edges). Epsom salts are a good source of supplemental magnesium. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer.

This problem can also be caused by chemical injury, such as drift from cleaners, paints, or chemicals used to kill moss on roofs. Sometimes the results of such injury may not show up for weeks or months.

Thanks for the quick responses.

Luis - I dont know what to do so you can see these, but if you have any other suggestions how to post them I'll try it. Check the Http address at the beginning or the end. Sometimes the addresses do not copy well.
I still have not figured how to include photos on my postings on gardenweb.com forums.

Rhodyman - Do you know how to treat this?

I planted all my rhodys and azaleas last fall around my porch. I want to have combination of different flowering colors. My aim is to have these grow to their mature size and form globular hedges, particularly with the azaleas.

If you like to see more pics please go to:

This is the diseased Rose Greeley in front of Rhody Chionoides:
http://s211.photobucket.com/albums/bb319/dmichelen/?action=view&current=IMG_3893.jpg

This is the diseased and dried Klondyke in front of Rhody Capistrano:
http://s211.photobucket.com/albums/bb319/dmichelen/?action=view&current=IMG_3904.jpg

This is Rosebud in front of Rhody Roseum Elegans:
http://s211.photobucket.com/albums/bb319/dmichelen/?action=view&current=IMG_3950.jpg

This is Purple Gem in front of Rhody Purpureum Elegans:
http://s211.photobucket.com/albums/bb319/dmichelen/?action=view&current=IMG_3905.jpg

This is Stewartstonian in front of Rhody Vulcan Flame:
http://s211.photobucket.com/albums/bb319/dmichelen/?action=view&current=IMG_3894.jpg

I actually know this was present in a plant I purchased last year, azalea Klondyke. Obviously it was my big mistake, I actually noticed something on the leaves when I purchase it, but my inexperience did not help me pass on not getting it. I wanted to get a yellow azalea and this was the last plant they had. I planted it in the fall last year only to watch the leaves completely get filled with this stuff. I striped the plant of all it leaves couple of months after I planted (maybe November 2006) in hope I could save the plant and eliminate the problem. To my disappointment the plant did not flower this spring, but started to send more new healthy shots from the base of the plant and the lower branches. So it is still alive and it does not look like the new growth has the disease yet. This spring after I noticed the buds did not do anything I assumed they were dead and I cut the plant to about 8" from the ground to give it a new start. Well see what will happen with it.

It the meantime during the winter I had another azalea (Laura pink flower ) that browned and died. For this one I did not even consider trying to save it because it was happening during the winter. By the time the temperature started to warm up here it was completely browned. Then I noticed another azalea close to it, started to get the stuff. The Rose Greeley azalea which I selected for its white flowering, and it was listed as a proven performer in my area on the Rhododendron society site. The plant past its bloom couple of weeks ago, and I deadheaded the spent flower. New grow immediately followed. Old growth petals had some of this white and brown stuff before it bloomed. Now I noticed yesterday the new growth is getting it too.

I contacted my local cooperative extension, and even brought them some samples of the plants. Unfortunately they have not responded to me.

This is extremely disappointing. It seems to be a disease that is moving from plant to plant. I have all my Rhodys and azaleas around my porch and I am afraid this is going to continue to spread. Before I set all this plants I did research how to prepare the beds, fertilizing, mulching, watering etcI really want to get to the bottom of this.

I really appreciate help.
Thanks

Most of you plants look good. The klondike is a deciduous azalea and has nice big buds. It should be coming out in bloom now.

I gave you the best advice I can. Compare the symptoms with the problems. Also, get a soil test to see what is causing the chlorosis.

If it is chemical injury, then it will have to go away on its own. All you can do is try to keep them healthy.

My website should help do that.

Thanks for the quick follow ups,

Unfortunately the Klondyke got some serious attack last fall with the stuff I am trying to control. Those large buds did nothing this spring, heartbreaking. They are dried.

I continued looking for information online to see if I could get more about this problem. I stumbled into some photos that looked very similar to what I see on my plants.

Look under lace bugs:
http://www.turfdoctorinc.com/common_lawn_prob.htm

Also:

http://www.keystonetree.com/pest6.htm

http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/HORT/FLOR/CP/GN2004_18.PDF

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7429.html

This site says that damage can have the look of chlorosis too:

http://county.ces.uga.edu/cobb/Horticulture/Factsheets/AzaleaLaceBug/azaleabug.htm

Upon reading I detect that lace bugs or thrips seem to be the problem. All symptoms in my plants are consistent to the descriptions on the above sites. I have access to microscopes. I cut a branched an examined it, and definitely I noticed some bugs under the leaves that resemble the photos I see of lacebugs.

Since there is a possibility any of these two might be causing the damage, can somebody suggest what products to applied and when? Hopefully it is as simple as applying a systematic or spray insecticide.
I will greatly appreciate suggestions
Thanks
David

Whitish specks on the upper surface of leaves and dark spots varnish-like on the bottom are symptoms of Rhododendron Lace Bugs, Stephanitis rhododendri, and Azalea Lace Bugs, Stephanitis pyrioides, small insects with transparent wings on under-surface of leaves.. This insect hatches early in spring as the new foliage begins to mature and its numbers may build to damaging levels with successive generations. Lace bugs reach their peak in late summer and do their worst in sunny, exposed sites. Spiders are important predators of lace bugs and since they shy away from sunny, hot places, plant your azaleas where there is some shade. Insecticidal soap, horticultural oil, or a systemic insecticide may spare your azaleas the damage if applied in spring when the first hatchlings are noticed. Care must be taken to spray the lower surfaces of the leaves where the lace bugs live. Moving a plant to an area with more shade may alleviate the problem. Lace bugs are more prevalent on certain varieties. The following azalea cultivars have resistance to azalea lace bug: Dawn, Pink Star, Ereka, Cavalier, Pink Fancy, Dram, Seigei, Macrantha, Salmon Pink, Elsie Lee, Red Wing, Sunglow and Marilee.

Rhododendron Lace Bugs, Stephanitis rhododendri, and Azalea Lace Bugs, Stephanitis pyrioides adults are about 1/8-inch long. The body is pale yellow. The lacy wings (very distinctive) are held flat over the back and are transparent with two dark spots present. The nymphs are black, spiny and smaller than the adults. The eggs overwinter partially embedded in leaf tissue. The eggs hatch in May. The nymphs mature into adults in June and lay eggs during late June and July. The second generation of nymphs appears in August. The overwintering eggs will be laid when these nymphs become adults. Lacebug adults and nymphs feed on the undersides of leaves by piercing the leaves with their mouthparts and sucking the plant juices. This causes a mottled, silvery or white discoloration, known as stippling, on top of the leaf where the chlorophyll has been removed. The undersides of leaves are covered with dark brown to black, sticky spots of excrement. Plant rhododendrons in shade to maximize the activities of beneficial insects. Varieties that are attacked by lacebug will recover if moved to shadier areas. They only get lacebugs in full sun.

The National Arboretum warns: "Excess nutrients (fertilizer) may promote larger than normal populations of azalea pests like lace bugs

Thrips, Thrips imaginis: This insect is a seasonal pest, causing most damage in mid to late summer. Signs of damage include silvering of the foliage and distortion of growing points and flower buds. The underside of leaves may be covered with excreta of the insect, which are like brown tar droplets. There are no effective specific biological controls and thus control can be difficult to achieve. Thrips are preyed upon by ladybirds and lacewings but these predators cannot control thrips in plague situations.

You might want to read up on all the uses of Neem oil. It is natural and safe to use and treats many pest problems as well as fungi.

That master gardener, Paul James, loves that stuff.

Perhaps you mean the insecticide, miticide and fungicide: "hydrophobic extract of neem oil". Don't be too awed by "natural". Arsenic and crude oil are natural. All materials need to be tested, even natural ones. Natural chemicals such as neem oil that kill a broad spectrum of insects also kill the beneficial insects, so this is not as attractive insecticide as a biological or other more specific controls.

Thanks all for the follow ups,

This is what I did:
I sprayed underneath the leaves with "Dual Action Rose & Flower Insect Killer Ready-To-Use" from Bayer.
After 5 days I applied the systematic insecticide "Tree & Shrub Insect Control" from Bayer. I also applied this to all other azaleas and rhodys.

I also sprayed with "Gardensafe Fungiside 3" Neem oil.

I removed the largely damage leaves. It seems that the infestation is out, but the plant looks stressed. Hopefully it bounces back during the summer with new foliage before the cool sets in.

Well see how it does.

Perhaps you mean the insecticide, miticide and fungicide: "hydrophobic extract of neem oil". Don't be too awed by "natural". Arsenic and crude oil are natural. All materials need to be tested, even natural ones. Natural chemicals such as neem oil that kill a broad spectrum of insects also kill the beneficial insects, so this is not as attractive insecticide as a biological or other more specific controls.

I'm not awed by the term natural. I'm awed by the fact that Paul James, a master gardener who is extremely particular about the controls he uses and recommends, highly recommends it.

Neem oil kills beneficial insects. James uses neem oil for cucumber and Colorado potato beetles.

Here is what Paul James actually said:

"For most bugs and beetles--those that eat plants, that is--he relies on insecticidal soap first. If that doesn't work, he uses a pyrethrum-based product or a product containing neem, a relatively new control that comes from the neem tree." [Episode GBY-608]

"Rather than reach for a product that's likely to destroy every bug in sight, try to target the specific pest with a specific product. James recommends BT for caterpillars; Neem for cucumber and Colorado potato beetles; horticultural oil or insecticidal soap for scale, mites and aphids. In fact, with BT, Neem, horticultural oil and insecticidal soap, you can control virtually any and every pest problem." [Episode GBY-1102]

"Think twice before using certain garden products, especially those that are oil-based such as horticultural oil or neem oil." [Episode GBY-1303]

Well I was referring to another episode, GBY 1402:

Pest-Controlling Oils
Today's horticultural oils are effective, low in toxicity and can be applied just about any time of year.
Gardening by the Yard : Episode GBY-1402 -- More Projects »
Products made from various oils have been used in the garden for centuries. Ancient Romans used mineral oil to control plant pests, while the American colonists relied on whale oil.

Beginning in the 1930s, the oil of choice was a petroleum product known as dormant oil, so named because it was applied during the dormant season. It was used primarily to control scale insects and mites on dormant trees and shrubs.

Today new superior oils also called highly refined oils or simply horticultural oils have replaced dormant oil. Theyre effective, low in toxicity and much lighter (that is, not as viscous). These oils can be applied just about any time, even during the growing season, and control not only pests but various diseases too, in particular fungal diseases.

The key to using horticultural oils during the growing season is to make sure the plants youre spraying arent water stressed; if they are, some damage could occur. So simply water the plant well the day before you spray.

Neem oil is an excellent product for controlling pests and diseases. "Its derived from the tropical neem tree," says Paul James, "and it works better than any other oil-based formulation Ive ever used."

Within the category of herbicides, new products seem to pop up every year, says Paul, including one introduced in 2005 that is made from clove oil. "In my experience, these oils control weeds best when temperatures are warm, say in the 80s or 90s," he says.

horticultural oil (Concern/Necessary Organics) - Woodstream Corporation
clove oil - St. Gabriel Laboratories
neem oil - Safer Brand

For more gardening tips from Paul James, visit the HGTV Video Center.

For neem to harm beneficials, the insect must come into direct contact with the product while still wet. Once dried, neem remains harmful only to those insects that feed on leaf tissues or sap. It is an anti-feedant, working as a growth regulator. It has also shown definite systemic action, both against feeding insects and certain fungal disorders.

laurabs,

Are you saying that Paul James was wrong before? When do we believe him? Shouldn't we consider the sum total of what he said rather than a quote out of context?

There is a place for Neem oil, but it is a broad spectrum insecticide and will kill natural predators such as the predators for scale insects. Natural predatation is the best control for scales, not neem oil. I am not an organic gardener, but I know the pitfalls of using broad spectrum insecticides. They create many new problems, especially scale problems. I personally seldom ever use any sprays or oils on my rhododendrons and azaleas and they have been doing well for 40 years. There are two reasons for me not spraying, 1) there hasn't been any reason to, and 2) I have a shallow well and don't want to poison my drinking water.

Not all problems should be solved by a spray. Many times the spray just creates a problem that wasn't there.