Question: We have noticed during the last two Augusts that our globe willow has spots of a white foamy substance on the trunk and branches. When we investigated, we saw small worms. At the same time, there were large amounts of sap running down the trunk and dripping off the branches. The smell from this sap was sickeningly sweet. Is the sap causing the worm issue, or are the worms causing the sap? G.W., Fort Worth

Answer: The smell could indicate disease. The worms may or may not be part of the problem. Remove any soil covering the base of the tree and follow my Sick Tree Treatment 

If the foam is coming from smooth-sided holes, borer insects are working on the tree and should be treated. Inject full-strength orange oil or d-limonene into the holes and seal the holes with my Tree Trunk Goop mixture (one-third compost, one-third soft rock phosphate and one-third natural diatomaceous earth; mix with water to make a paste). Stop using synthetic fertilizers.