Pest Of The Month: Angular Leaf Spot
March 1, 2007 
Identification
Foliar symptoms consist of water-soaked lesions on leaves, which expand until delimited by veins, giving the lesions their characteristic “angular” appearance. Under humid conditions, the water soaking is accompanied by a milky bacterial exudate that dries to form a white crust on the lower surface of the lesion.
Infection can also occur on petioles, stems, and fruit. Lesions often display a crusty, white exudate. Spots on fruit are usually smaller and circular in shape with a tan center. Lesions on young fruit may cause the fruit to curve.
Survival And Spread
Angular leaf spot is seedborne. The bacteria can over-winter in crop residue and on seed. On seed, the bacteria are present beneath the seed coat so that upon germination the cotyledons are infected. The bacteria then spread within the plant and from plant to plant by splashing rain, and also by insects, pickers, and equipment. Spread is enhanced when foliage is wet from rain or dew and through abrasions caused by wind-blown sand.
Mangement
As with most vegetable diseases, problems with angular leaf spot can be reduced using an integrated pest management approach using a number of control tactics. The primary cultural control begins with clean, disease-free seed.
Crop rotation with non-cucurbit crops is helpful for reducing the incidence of angular leaf spot, as is cultivation of the soil during dry periods to reduce the chance of bacterial survival on debris. Where the disease is present, application of copper fungicide, as a foliar protectant will assist in control. During favorable periods for disease development and epidemic conditions, use of copper may be ineffective.
This article was contributed by Gene McAvoy ([email protected]), a Hendry County Extension agent in LaBelle.
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