Southeastern Apple Production

Plant Pathology

Disease Management

Brooks Spot

Mycosphaerella pomi

Brooks spot, caused by Mycosphaerella pomi, occurs on susceptible cultivars throughout the Southeast. Light infections often go unnoticed since lesions are not very distinct.

Symptoms

Infections by M. pomi are small and are frequently found on the blossom end of the fruit (Fig 1). Lesions are irregular in shape, shallow, and primarily associated with the peel. There is no corking beneath the lesions as found with cork spot or bitter pit (physiological disorders) (Fig 2). Spots appear green to dark green on yellow or green fruit. Spots on red fruit appear as small dark green islands within the skin. Leaves become infected in May and June, but symptoms do not appear until late summer or early fall when small purple spots appear (often near veins)


Fig 1. Infection spots	Fig 2. Corking = NOT Brooks spot	Fig 3. Infected leaf

Disease Cycle

M. pomi overwinters in leaves on the ground and produces inoculum in pseudothecia in these leaves in the spring, much like the apple scab fungus. Spores mature during the 4 to 6 week period after petal fall and are discharged during rain, initiating infections. There are no secondary cycles during the growing season.

Control

Rome, Stayman, and Golden Delicious are the most susceptible cultivars widely grown in the Southeast. New cultivars that appear susceptible include Braeburn, Cameo, Fuji and Suncrisp. Infections occur on Delicious but are not common. Where the disease is a problem, fungicides should be applied on a 2-week schedule from the period beginning at petal fall and extending through second cover. Because the fungus overwinters in leaves on the orchard floor, shredding leaves after leaf fall may help reduce the inoculum. It is very important to maintain mites below 10 per leaf in orchards with a history of the disease in order to minimize defoliation. Shredding leaves or applications of urea to leaves just before or after leaf fall may reduce the inoculum. The strobilurin fungicides Flint and Sovran have shown good activity on the disease when applied in a sequence of three sprays. A threshold for beginning the applications has not been established, but the disease incidence should not exceed 40% before the first application is made.

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.

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Turner Sutton
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Format updated March 29, 2011