Oops. No photo. Wants me to sign in.

Root rot (Phytophthora) is common. So is inadequate summer watering. And they don't like hot sun beating on the roots, even if watered. Another widespread thing here now is foliage mildew. This often causes premature dropping of leaves, has become pretty serious. I haven't planted a new rhododendron on my place for years, it seems the most interesting kinds are the most susceptible.

If they had been planted rather close to the house, it's quite possible the soil is not sufficiently acidic for their liking. Concrete (house foundations, driveways, walkways, etc.) leaches lime indefinitely (decades) and this can raise soil pH in the immediate area significantly. While NW soils tend to be acidic, most are only slightly acidic - sufficiently so for most rhodies in most situations, but not if receiving the effect of this lime leaching. You see this situation all the time with foundation plantings of rhodies that are struggling and the lack of adequate pH will result in chlorosis and in extreme cases, leaf drop.

The other common problem is planting too deeply. Rhodies and azaleas should be planted so that the top of the rootball is slightly above existing soil level. Mulch lightly to cover and to hold in soil moisture. Too deep a planting will result in a slow failure of the plant over time.

Phytophthora is usually fatal. If you have been having this problem for some time, then phytophthora is probably not the problem, though wet roots could still be the problem. Mildew is a real possibility. Also, chelated iron is not always a cure for chlorosis.

Mildew
Light green or yellowish patches on leaves sometimes accompanies by brown spots on the back side of leaves is a sign of Powdery Mildew (Microsphaera azaleae). One of the puzzling aspects of this fungal problem is the fact that two different affected rhododendrons vary in appearance. Rhododendron cultivar 'Unique,' for instance, shows almost no upper leaf changes, other than occasional very faint lighter yellowish areas, while the underside of the leaves will be completely covered in brown spots. A deep green leaf may begin to show lighter green patches, and these areas will gradually become more yellow. Another cultivar, 'Virginia Richards,' gets brownish purple spots on both tops and bottoms of leaves. This common disease is named Powdery Mildew despite how little the symptoms resemble the familiar fungal disease often seen on roses and azaleas. Usually the disease doesn't produce the familiar white powder-like spores, although late in the summer some may become visible. The disease manifests instead as color changes in the leaves, followed by defoliation toward the end of the growing season. Many rhododendrons, if basically healthy, will coexist with the disease and seem to outgrow or at least survive the symptoms. Last year's leaves, once they have been hit by the disease, will always have it, with symptoms persisting from year to year until the leaves drop off. High relative humidity at night and low relative humidity during day with 70-80 F (22-27 C) temperatures is ideal for the disease to flourish.

* Keep rhododendrons healthy to help them manage this problem. If you notice symptoms on last year's leaves, consider protecting the new growth with a fungicide . Apply it now to the new growth as it expands, before symptoms appear on this spring's leaves. Fungicides won't get rid of the existing problem on old leaves. A new fungicide, 'Remedy,' which is a potassium bicarbonate (made by Bonide Company), is registered for the problem. Thorough leaf coverage is necessary with all fungicides. Fungicides containing sulfur (such as Safer Garden Fungicide RTU) are also registered. Others are Funginex (sold as Ortho RosePride Funginex Rose and Shrub Disease Control Concentrate.) Be very careful to read all label instructions, and wear protective goggles and gloves. Funginex can be corrosive to eyes. For more information see the section above on 'azalea powdery mildew'. The symptoms are different, but the organism and control are the same.
* Rhododendrons that have been hybridized with Rhododendron cinnabarinum as one of the parent plants do get the disease severely. Two of those are 'Elizabeth' and 'Lady Chamberlain.' The Cornish Cross hybrids, including 'Virginia Richards,' 'Seta' and 'Mrs. G.W. Leak' seem vulnerable also.

Chlorosis
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.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

Old hybrid rhododendrons here often have old knobbly swollen stem portions where Phytophthora attacks to the stems have deformed them. Some of these deformities look like they go back for some years. I doubt rotting of the roots by water molds promptly kills the whole shrub, even where there is a branch dieback that gradually eats the top of the rhododendron away this can drag on for years.

bboy, you are correct there are many types of phytophthora. Some attack stems and others kill roots.

Phytophthora Root/Crown Rot, Phytophthora cinnamomi: The fungus Phytophthora causes one of the most common disease problems in the landscape for rhododendrons and azaleas. This fungus is a "water mold," and thrives in poorly drained or wet conditions. A wilted plant is usually the first sign of trouble. Rhododendron leaves will curl inward and droop. This is a serious, widespread and difficult-to-control fungus disease affecting a wide range of plants . The symptoms of Phytophthora root rot vary with the cultivar. Some cultivars fail to grow or grow very slowly with pale green foliage and may die after several years. Others suddenly wilt and die within a few weeks. Roots are reddish-brown, brittle and often limited to the upper portion of the media in a container or very close to the soil surface (upper 2 inches). The reddish-brown discoloration advances to the larger roots and eventually to the lower part of the main stem. Phytophthora root rot is favored by high soil moisture and warm soil temperatures. The disease does not occur as frequently and may not be as severe on well-drained sandy soils as in heavy clays or poorly drained soils, etc. The disease is common and severe in areas where run-off water, rain water from roofs, etc. collects around plant roots. Setting woody plants deeper than the soil level in the nursery or container, over-watering plants, or long periods of heavy rain also favor disease develop especially in shallow soils with underlying rock or compacted hard pans. Phytophthora root rot must be prevented as chemicals are often ineffective in controlling this disease after aboveground symptoms appear. This root rot is the major killer of rhododendrons and azaleas. It develops when roots are growing in wet conditions and is more prevalent in warm summer conditions. Plants infected with crown rot have roots which become clogged with brown fungi internally. When the roots get blocked and the plant wilts and dies. There is not much of any cure for crown rot. Some varieties of rhododendrons are vulnerable (Chionoides, Catawbiense Album, Nova Zembla) and some are resistant (Roseum Elegans, Scintillation, PJM). Sphagnum moss and bark dust combined with good drainage seem to prevent crown rot, but do not cure it.

Phytophthora Dieback, Phytophthora cactorum or citricola: Dieback of hybrid rhododendron is a foliar disease caused by several species of the fungus Phytophthora. In North Carolina, P. cactorum, and P. citricola have been isolated from diseased plants. Rhododendron dieback is primarily a problem on container-grown hybrid rhododendrons in nurseries. This disease is very rarely observed in the landscape. The fungus survives in the soil and cannot be eradicated once an area is infected. Lesions first appear as chocolate-brown spots on young, expanding foliage and stem. If the leaf spots reach the midrib of the leaf as they grow, the fungus will grow into it, and down the petiole until it reaches the stem. On the stem, a diamond shaped canker is formed. This will continue to grow until it completely surrounds the stem. The portion of the stem above the canker then dies, and turns completely brown. On older plants, the fungus may grow down the stem into a healthy leaf, causing a narrow brown band to appear along the midrib. This band will expand in a V-shaped pattern, with the widest portion at the base of the leaf. These leaves usually fall off within 1 to 2 weeks. The fungus grows from initial lesions down the stem into older leaves. Lesions on mature leaves are characteristically wedge-shaped, extending from the petiole toward the leaf margin. Infection spreads rapidly in warm days. The fungus progresses slowly in older woody stems, but can kill any size plant. Phytophthora dieback is favored by hot, wet weather during the summer months. The fungus is spread from infected plant debris on the container base and between plants by spores in splashing water. Free water on the leaves is needed for infection by the spores. Infection occurs on the lower surface of expanding new leaves. Nurseries where rhododendron are grown under shade and irrigated by overhead sprinklers provide ideal around plants often occurs in nurseries using pine bark or plastic as a container base and increases the spread of the fungus by splashing. Excessive use of nitrogen fertilizer, which increases plant succulence, particularly during August, increases plant susceptibility to Phytophthora.

applekin, I'm not finding the photo of your plants available either.

As gardengal mentioned, planting too deeply so that the surface roots cannot function can cause nutrient deficiency, eventual death. The same results take place when the rootball isn't loosened well enough at planting time - when the nutrients in the potting medium are exhausted, the plant will fail (or the potting medium becomes so dry that the plant dies from drought even though the surrounding soil outside the compacted rootball is moist)

Chlorotic symptoms can also reflect the lack of elements other than iron - Magnesium deficiency can be determined by spraying the foliage with 2 T Epsom Salts (magnesium sulfate) per gallon of water.

Anything that can damage roots (leaving too few remaining roots to supply top growth with nutrients) can cause chlorosis - root weevil larvae (you would see the damage from adults, notching of leaves), fertilizer burn, poor drainage.

I would liked to have seen the photo...but if you've moved your shrubs, best treatment may be to mulch them well, keep them adequately watered (if we do come to the point where it stops raining:)), see what they do in their new site.

Gee, all this discussion and no pictures to show what is truly happening.

Root rot is always a possibility with rhodies but so are other things which can lead to few and/or off-color leaves, small new growth, and more.

Applekin -- is it possible to fix the link to your pictures? Likely they would help provide a diagnosis.

I haven't quite figured out the photo loading part.
try copy/pasting this link:
http://www.kodakgallery.com/PhotoView.jsp?collid=864017190110.370266190110.1172971535709&photoid=170266190110&folderid=0&view=1&page=1&navfolderid=2007&;

or this one:
http://www.kodakgallery.com/PhotoView.jsp?collid=864017190110.370266190110.1172971535709&photoid=770266190110&folderid=0&;

Both those links give me the same result; I need to sign in.

...using your login and your password. It is not a public site.

I read the info on problems with rhodies with interest. I planted a beautiful lavender one last fall in front of the house, and it looks horrible. The leaves are yellowing and spotted and, quite frankly, it seems to be dying. We did have a very cold 2 or 3 months, with ice storms, but the plant was sheltered. The green acuba right next to it looks fabulous, and the daffodils are coming up.

So, could it have gotten too wet over the winter? If I trim it down and transplant it, will it survive? I have plenty of well-drained spots in the back yard.

Thanks for all the interesting info.

Yellowing and spotted in not root rot.

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. There is a tonic that remedies some cases of chlorosis.

Yellow mottling on the upper surface of leaves and black sooty mold and transparent insects on the bottom are symptoms of Azalea Whitefly (Pealius azaleae.) and Rhododendron Whitefly (Dialeurodes chittendeni.). These may also cause the following symptoms:

Small white spots on the underside of leaves and small white flies on under-surface of leaves is also an indication in infestation of Azalea Whitefly (Pealius azaleae.) and Rhododendron Whitefly (Dialeurodes chittendeni.). They are more prevalent on certain varieties and on plants grown in protected areas. These small white flying insects look like an aphid with wings and suck on the underside of foliage, leaving white spots where it has been. Heavy infestations cause the margins of terminal leaves to cup. These infested leaves will eventually turn yellowish and appear wilted. The lower leaves become covered with honeydew, followed by sooty mold (a black coating). To check for the presence of whiteflies, shake the terminals of white azaleas to flush out adult whiteflies which look like tiny white moths. Examine the lower surfaces of leaves for the presence of nymphs, which are flat, yellowish green, and resemble scale insects. All stages occur on the under sides of leaves. This whitefly is usually limited to varieties of the snow azalea, Rhododendron mucronatum. If the infestation is light, little or no plant symptoms are evident, and if beneficial insects are present, spray the undersides of leaves with insecticidal soap or a horticultural oil at the 2%summer rate. If the infestation is heavy use a registered residual insecticide such as Malathion, Diazinon or Orthene.

Yellowing of leaves surfaces, often with brownish burned areas, occurring on leaves that are more exposed to sun, is caused by more sun exposure than the plant is able to tolerate. Some varieties need shade, while all plants that have been protected from direct sun will be tender until hardened off by gradual exposure to sun light. Possible solutions are to give the plant more shade or move it to a more protected site.

Yellowing and dropping of leaves is normal toward the end of the second summer on the small-leaved lepidote rhododendrons. These should have dense enough habit that this doesn't matter. The larger-leaved elepidote rhododendrons keep their leaves for 3 or 4 seasons. Like all evergreen plants, rhododendrons and azaleas periodically lose some of their foliage, and the leaves may turn yellow, red, or purple before they fall. Often the only leaves that remain are those that surround the flower buds at the tips of the branches. This characteristic is linked to the genetics of the parents used to breed garden azaleas. The degree of leaf coloration or loss is a function of parentage and not the severity of the winter. In unusually cold winters, certain azaleas may lose more leaves than they would in mild winters.

Uniformly yellowish-green leaves is often just the need for more nitrogen. This will be more noticeable in the full sun. Some less sun tolerant varieties will always be light green in full sun.

Yellowing of leaf edges has been noted in gardens where sandy soil conditions or root competition with other plants caused insufficient soil moisture and nutrients. Usually incorporating organic material in the soil and removing the plants with the competing roots solved the problem. Care must be taken not to disturb the roots of the rhododendrons and azaleas. Hence it is best to prepare the soil adequately before planting. The tops of most competing plants can be removed leaving the offending roots in the ground and the offending roots will simply decay and pose no problem.