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Pumpkin Bacterial Spot

Spots on your pumpkins? The following information will explain what it may be.

Nashville, Ark. – With fall fast approaching and hopes of cooler temperatures pumpkins are a fall favorite for many. Bacterial spot of pumpkin caused by the bacterium Xanthomonas campestris pv. cucurbitae, can cause more than 50% yield losses in severely infested fields. Cucumber, pumpkin, summer and winter squash, watermelon, and gourds are all susceptible.

The first symptoms on leaves are small yellow spots. The spots become small, dark, angular lesions surrounded by a yellow halo. The centers of the lesions become dry and translucent with age. As the lesions expand, they follow the veins making large necrotic wedges on the leaves.

However, the most damaging symptoms appear on the fruit. Fruit lesions begin as small, slightly sunken, circular spots, 1/16 to 1/18 inch in diameter. As the lesions enlarge, the cuticle and epidermis crack. Larger lesions may have a scabby appearance with tan, raised blisters. Saprophytic fungi often colonize the older lesions, giving them a pinkish-white or green color depending on the species of saprophyte involved. The unsightliness of the lesions diminishes the marketability of the fruit as well as leading to significant rot in the field and in storage. The pathogen is seed-borne and can also survive in crop residue. Bacterial spot is more of a problem during high temperatures coupled with rainy weather or overhead irrigation. Inoculum is splashed onto young fruit before it develops its protective waxy cuticle.

Good sanitation and crop rotation with non-cucurbit crops help limit inoculum in the field. Only clean seed should be used; therefore, it is advisable to not save seed from a previous crop. Copper fungicides may be applied during early formation and fruit expansion to protect developing fruit. Once bacterial lesions are observed on mature fruit there is nothing to be done except to practice ruthless culling of diseased fruit.

For more information, you can visit, or send an email to Howard County Extension office is still working and is there for all the residents in Howard County during this time. 

By Samantha Kroll
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture

Media Contact: Samantha Kroll
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
421 N. Main Nashville AR 71852
(870) 845-7517


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