The yellow leaves with green veins are definitely not caused by insects. They are strictly a nutritional problem. By spraying with insecticides indiscriminately you may give yourself a bad case of Lace Bugs. One of the main ways to control Lace Bug is with natural predators, i.e. spiders. That is the reason Lace Bug is a problem in sunny locations is because spiders don't like sunny locations. Unfortunately some of the most severe problems in the yard start by using a chemical that causes more harm than good. There is a very long list of such chemicals. The chemical companies love people who do this. Every time they create a new problem, they buy more chemicals. The best advice is to identify the cause of any problem. Then determine if it is worth doing anything about. If so, then find a solution that doesn't cause more problems. Definitely don't go by the information from the company or store selling the products. Common sources of good information are your county agent and local horticultural clubs.

Some of them were planted in October, and some were planted in March. I watered them everyday for the first month or so. If I didn't, they would begin to droop. Now, they get watered 3 times per week with the water sprinkler, and I use a soaker hose on them for about 2 hours once a week.

This is not the best time to use a systemic. Your efforts might best be used to apply horticultural oil a few times during the fall and winter season, making sure that you get the spray on the underside of the leaves, and down the stem. Get rid of the fallen leaf debris over the winter, as eggs may be embedded in those, as well as the leaves still on the plant. That's why a systemic is not effective at this time of year...you need to concentrate on the eggs! Early next spring, begin treatment of ALL of your azaleas. You could continue with the oil sprays and you could use insecticidal soap, or you could go ahead with your systemic application if you feel that you must. The secret to lacebug control is catching an outbreak before it gets to the point where the leaves are turning yellow and falling off. Lacebugs are easy to spot, and can be located even on seemingly healthy plant if you keep your eyes open. Imidacloprid, the active ingredient in the Bayer systemics, is under very severe scrutiny all over the world, and some countries will probably ban it before too long. It is believed to be causing severe problems with honey bees and other pollinating insects. Just a thought.

Yellow leaves with green veins is a well understood condition called chlorosis. However, it is so well understood that it has many causes. Although it indicates an iron deficiency, the most common cause is lack of acidity and powdered sulfur is a remedy. A soil pH test will verify this. Powdered sulfur is slow acting but long acting which is a good combination. Do not use Aluminum Sulfate. They use it on hydrangeas but it will kill rhododendrons and azaleas. The desired pH is 5.5. 3 Tablespoons of powdered sulfur per square yard will lower the pH by about 1/2 a point. The other causes of chlorosis are: 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, magnesium deficiency or too much phosphorus in the soil. 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. For a quick but only temporary improvement in the appearance of the foliage, ferrous sulfate can be dissolved in water (1 ounce in 2 gallons of water) and sprinkled on the foliage. Some garden centers sell chelated iron that provides the same results. Follow the label recommendations for mixing and applying chelated iron. 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.