I've had numerous raspberry plants for about 15 years and they have always produced a good crop of raspberries, until last year, when there were none. This year a few of the plants have berries, but the majority don't. The plants are very healthy looking, so I don't know what the problem is. Are my plants too old or what can I do to get raspberries again. Thank you, Cathy Shaner
Here are a few reasons why your plants have stopped producing.
Sun. Have some trees grown up around them, cutting off the daylight?
Fertilizer. Not too little, but too much. Too much nitrogen makes the plants produce a lot of green foliage at the expense of flower and fruit.
Bees. If you have flowers but no fruit, perhaps something has reduced your bee population.
Here is an interesting reference that will give you a few more possibilities: