My guess would be you have lacebugs on the leaves, they leave the leaftops looking like they have been heavily salted (white spots throughout the green) and their leavings are on the leaf underside, and are brown. Get an insecticide (I have used Rose ready mixed Insecticide successfully - I think it was Ortho brand) and spray thoroughly, making sure to get the undersides of the leaves.

The yellow leaves could be chlorosis - caused by high soil pH - is your soil acid enough? - use an acid fertilizer this year (like Miracid)

Thank you, scenter! I will try both.

I would encourage you to try less environmentally obtrusive methods to remedy the problems. Ortho products tend to be pretty toxic and Ortho remedies that are registered for lace bugs contain acephate, an organophosphate (attributed to neurological damage). Lace bugs are more prevalent on plants located in bright sunny exposures - locating your azalea in partial shade should reduce their presence as well as be less stressful for the plant. They can also be controlled quite effectively with insecticidal soap or Neem oil, both of which are considered very low toxicity organic controls.

Proper soil conditions are important as well. An acidic, well-draining soil rich in organic matter is ideal. If your soil is not sufficiently acidic, incorporating peat or cottonseed meal or an application of agricultural sulfur can help adjust but be sure to test for current pH levels before amending. It is just as likely that the azalea was planted too deeply or is suffering from sun stress or poor drainage - these can all produce yellowing foliage as well.

If fertilizing is warranted - again test soil before applying - an organic formulation for acid loving plants (Espoma produces one for east coast gardeners, Dr. Earth or Whitney Farms are available for west coast gardeners and there are others as well) is going to be more beneficial for both soil life and the plant than Miracid.

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 azaleas or 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 azaleas, 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 azaleas 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.

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

Anne, a photo would be very helpful in diagnosing your plant so you don't waste time and money with the wrong product if you choose to treat....we try to be helpful but you're leaving us to our own interpretations from your description - which is not a criticism of your wording :)

Something showing the azalea as it's planted, and if possible a second photo representing both the top and underside of an affected leaf?

Many here use Photobucket....

Here is a link that might be useful: Posting a photo GW Computer Forum