Have had problems with aphids residing on the underside of leaves of my Kentia and have treated the plant with diluted dish washing liquid spray which seems to have done the trick in removing them. However, the Palm is not doing well, the leaves are generally browning and look distinctly unhealthy. I did repot the palm about 6 weeks ago and felt that the palm was becoming pot bound so trimmed some roots away, that could have been a serious mistake given its appearance now.
Balcony Kentia Palm
Certified GKH Gardening Expert
This has undergone some very harsh treatments. There is a chance that it will recover, but trimming the roots on these is never recommended. They will prefer being rootbound.
The dish soap works on many plants, but also many plants are sensitive to this treatment. This would be one of them. I recommend neem oil for aphids. Alternatively, you can slice and boil hot peppers in water. Let this cool, strain, and spray. This is a much more gentle, and effective treatment.
Unfortunately, there is very high chance that this plant will be on its way out now. If you are very careful, and give it absolute perfect care, then there is still a chance for it.
This article will help you in the care of these in the future: https://www.gardeningknowhow.com/houseplants/kentia-palm/howea-forsteriana-kentia-palm.htm
Many thanks for your answer and advice. I'll give it some tender loving care over the next days and weeks and see if I can bring it back from the brink...........