Q; Have bay tree in tub on patio – approx 6 years old. White spots appearing on underside of some leaves – look like emulsion paint! Also some leaves turned brown. Is that frost damage?
A: The white is most likely scale insect. If you don’t use it as an edible crop but treat it purely as ornamental you can spray with Provado which should over a period of time eliminate the insect within the white on the back of the leaves. The browning could be winter damage, feed at 2-3 week intervals with a good liquid feed and it should grow out of it.