I live in Montreal and I have a grapefruit tree. It spends the summers outside but when I bring it in for the winter it drips a sticky substance all over everything. It this sap or a bug infection? I do see little black spots on the bark but no bugs flying about.
Hi, Well my guess here is that your tree has Scale, which is an insect that produces a honeydew like substance on the stems and leaves. Scale insects don't really look like insects. Instead they look like flat, tan or bown fingernail type growths on the stems and branches. Scale is VERY difficult to eradicate if it's well established, but you can try using a houseplant insecticide that lists Scale as an insect it will kill. Frankly, when my plants get Scale I toss them because it's such a nightmare to get rid of. If you have only a few Scale on your plant you can attack them with a Q-tip dipped in rubbing alcohol. Of course, another pest that causes a honeydew like substance on leaves and stems are aphids. These creatures look like large grains of salt and pepper and generally can be found on new growth. Aphids are easy to eradicate with Insecticidal Soap which you can buy at garden centers. So, examine your plant to see which of these pests your plant might have, but since this is a long term problem, my money is on this being Scale. Good luck.