Help for a dying palm tree?
I bought an indoor palm tree last year; don't know what variety it is. It's about 7 feet tall. Two months ago it began showing small amounts of dusty white in one or two places. I washed that off. I saw some webby material where the leaves join the main part of each frond, again not much, and I washed it off. I have not been able to trace these or to find any visible insects, but the leaves are still turning brown from the tips and dying back. I have removed more than half of its fronds and it is still ill. I tried misting it with water, and on presumption that it is a pest, spraying it with limonene diluted, and with a very diluted insecticidal soap. These appeared to have no effect. I would hate for my formerly lovely palm to die.
The "webby material" which you described is a sign that your palm is infested with spider mites. Spider mites are very small and difficult to see. The dusty white substance is probably dried sap from the palm fronds where they were pierced by the spider mites which eat the sap. Using insecticidal soap is a good way to control spider mites. Be sure to follow the directions on the container. The application will have to be repeated until you no longer see any evidence of the spider mites.
Palms like warm temperatures and high humidity. They prefer 70 to 80 degrees during the day and 60 degrees at night when actively growing; in the winter they can stand it slightly cooler. Giving the leaves a warm shower now and then is beneficial (for many reasons), as is misting with distilled water. Never use tap water because the chlorine will harm the palm. The browning of the tips of your palm's fronds indicates a lack of humidity.
It is also possible that your palm is suffering from salts building up in the soil. If you notice a crust forming around the edge of the pot, it will be necessary to leach the container. This means placing it in a bathtub or outdoors in summer and running warm water through it to wash out the offending salts. Let the water drain out and then do it all over again a few more times that day. If you decide to use a liquid houseplant fertilizer instead of time-release, leach monthly. It is also a good idea to water the palm with distilled water, not tap water.
Palm trees are tricky houseplants to grow in our northern homes in the winter months.