I have an Azalea inherited from the house we bought last year (not sure what kind of Azalea this is) it was blooming very well with orange flowers this spring, but I notice the foliage color is too yellow-ish comparing to the Azalea pictures on google. and the new leaves are even more yellow. in addition, it is not bushy at all.
Is this Azalea sick or have some sort of nutrient deficiency?Can I use those shrubs spikes to give it some nutrient? Also, what pest is eating it?
Your azalea looks like one of the Northern Lights Azaleas. There are a couple that are in the orange to salmon colour range. Yellowed leaves, known as Chlorosis, is caused by a nutrient deficiency. Azaleas and Rhododendrons need an acidic soil. If the pH is too high i.e. alkaline, then the plants cannot take up some nutrients, especially iron and manganese. You can buy a simple pH testing kit at a nursery or some hardware stores. If the pH is above 6.5, then you should add sulfur or iron sulfate to the soil or use a sulfate spray for a more immediate result. Check the link below for good information about how to care for your azalea including how to deal with various problems like Chlorosis.
The notched leaves could be caused by a Black Vine Weevil or by a Leaf-cutter bee. A previous question on our site provides information regarding weevils as well as other Azalea pests. However if the notches are caused by bees, keep in mind that these bees are important pollinators. They are solitary bees and simply cut off bits of leaves to line their nests so are unlikely to cause more than minor damage to your plant.
https://www.torontomastergardeners.ca/askagardener/northern-lights-azalea-hybrids-caterpillar-pest/