Q:

What's causing this severe yellowing and spots on areca palm leaves?

I've got an areca palm that's around 3 years old, and until the end of summer last year it was thriving.
Fed, watered and misted regularly over summer months, with watering reduced over winter months but misting maintained.
Summer 2018 it was thriving with lots of new growth, however around October time it took a big down turn, and the leaves started to turn and die as pictured below, and now my palm is about a third of the size it used to be.

There doesn't look to be any root rot, I can't find any pests/bugs on it, the soil has never been allowed to dry out, yet the sheer brightness of the yellow, the dark spots, and the lack of green in the leaves in the last picture has got me stumped. Any ideas?

A:

This is two common problems for areca palms: over watering and spider mites.
The brown circular spots are fungus/virus/bacteria which thrive when the growing medium is kept too wet.  Reduce the frequency of watering until the top inch of soil is dry.  Then water enough that water runs out the bottom of the pot.  Do not let it sit in water.
Increase the amount of light and keep it drier and the plant will outgrow this problem.
On the underside of the leaves you will see tiny grains of salt which are spider mite egg cases. The pin prick look on the leaves is where the mites have sucked out the plant juices. You might need a magnifying glass to see them.
Take cloth or rag and soak in about 10 to 15 ml of dish soap to one litre of water.  Then rub the underside of every leaf with the cloth.  Do the whole plant and repeat three times every six days.  Repeat the three treatments if necessary.  
It is important to remove the soapy film from the leaves. You can rinse with a cloth soaked in water or put the plant in the shower.

