Causal Agent:
Phytoplasma

Vector:
Brown Leafhopper (Orosius argentatus)

Distribution:
Australia, Brazil, India, Israel, Russia, USA

Symptoms:
The primary symptom of this disease, and the one for which it is named, is the enlargement and abnormal development of the flower buds. Sepals may not separate as the flower opens, and the buds will be swollen and green. Other symptoms include a thickening of stems, proliferation of small side-shoots and aerial root initials. Shortening of the internodes, an erect growth habit and the development of an overall yellowish appearance of the plant may also occur. Fruit may be small and deformed.

Conditions for Disease Development:
This phytoplasma can survive in crops such as hot pepper, lettuce, eggplant and potato, as well as weeds such as dock, lamb's-quarter, nightshade, sowthistle and jimsonweed, and is readily transmitted to tomato by the common brown leafhopper. Transmission occurs when leafhoppers carrying the phytoplasma migrate to tomato and feed.

Control:
Big Bud is generally only of occasional importance. Removing host weeds adjacent to tomato plants and controlling the leafhopper vectors with an insecticide program are usually sufficient.

Enlarged swollen flower buds.

Close-up of enlarged flower bud.

Fruit symptoms showing deformations.