Garden Pests and Diseases: My Phoenix Robilini is under attack, 1 by nipandjas

nipandjas wrote:
Hi we have been battling an unknown pest that turns leaves black ,new fronds grow and are healthy for awhile but then succumb to the same fate ,it is now in all our palms , started in one we removed and destroyed it and them it showed in the rest , have watered ,fertilised ,mancozareb fungicide but to no avail. Can any members advise of what my photos are showing and how to deal with it.The white powdery on underside of leaves we have never noticed over the 3 years . We are unsure if this is contributing or is a new pest.