The plant's own resin
Not a problem. Tomatoes, and to a lesser degree aubergines and some herbs, are covered in glandular hairs that release a sticky aromatic resin when brushed. It transfers to hands and clothing, smells strongly of the plant, and is present on a completely healthy specimen — it is the reason a tomato plant smells of tomato. It is routinely mistaken for honeydew from an insect that is not there.
What brings it on
Stickiness on the stems and the undersides of leaves, strongest on the growing point and on the side shoots, on a plant growing vigorously in warm weather. It is most obvious when tying in or pinching out, and there are no insects, no black sooty deposit and no sticky film on the floor or the leaves beneath.
source
Horticultural consensusmoderate confidence
- Royal Horticultural Society: Tomatoes — growing
Checked 2026-08-13
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Nothing to prevent. Recognising it is the point: the alternative diagnoses all lead to spraying a crop that is in flower, and the resin is a defence the plant produces on purpose.
source
GrowingHQ editorial positionhigh confidence
A framing decision about what the differential is allowed to conclude rather than a horticultural fact.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13
Dealing with it once it is there
- Nothing. Wash your hands — the stain is stubborn but harmless. If you want to be certain it is not an insect, look at the UPPER surface of the leaves lower down the plant and at whatever the pot is standing on: honeydew falls, so it collects there, and resin does not.
source
Horticultural consensusmoderate confidence
- Royal Horticultural Society: Tomatoes — growing
Checked 2026-08-13
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.