Nursery Location:
120th & Maple, Omaha, NE

Our Hours:
Mon–Sat 8:30am–8pm
Sun 10am–6pm

4th of July
8:30am-4pm

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Common Fruit Tree Diseases

Cedar-Apple Rust

Cedar-apple rust is one of the most noticeable and destructive diseases of apples in Nebraska. It occurs wherever apple and juniper trees are grown in close proximity to each other.

The cycle begins when corky, brownish-green galls are seen on infected cedar trees in the fall. After spring rains the woody galls form, and spores (fungus seeds) are released. These spores are carried by the wind to apple trees where they germinate and produce the typical rust lesion on leaves, fruits and occasionally on twigs.

During June and July, yellow to orange spots develop on the upper surface of leaves. Later, many small, cup-shaped structures are produced on the underside of the leaf directly below the upper surface lesions. The "cluster cups" can also occur on fruits, marring their shape and appearance.

RUST REACTION OF SELECTED APPLE VARIETIES

Resistant	Intermediate	Susceptible
Red Delicious	Golden Delicious	Jonathan
Early McIntosh	Haralson

When lesions develop on fruit, the quality of the apple is reduced even though it remains edible. This reduction is due to the uneven or knobby appearance caused by the developing lesions. Trees that have been exposed to severe rust infections are often weakened and have a reduced fruit set the following year. On occasion, they may fail to set any fruit the following season.

If rust is a recurring problem, fungicides may be applied on a routine spray schedule. Correct timing of the fungicide application is critical, since the fungicides are preventive and will not cure an infection once the fungus has become established. The first application should be at flower bud break or early pink bud stage followed by a second application at petal drop. Three of four additional applications at 7 to 10 day intervals usually provide good control of the disease for Cedar-apple rust.

If you follow the Mulhall's Fruit Tree Schedule for apples, you will use Ferbam or Mancozeb on application number three, four, and five added to the regular orchard spray you have chosen (multi-purpose orchard sprays do not contain Ferbam or Mancozeb). You will then make three more applications timed 7 to 10 days apart with just the Ferbam or Mancozeb. Continue using the multi-purpose orchard spray, but apply at slightly different intervals.

Recommended fungicides for cedar-apple rust control

Chemical	Rate / Gallon	Rate / 100 Gallon	Time before harvest
Ferbam 76 WP	2½ Tbs.	2 lbs.	7 days
Mancozeb	2 Tbs.	2 lbs.	30 days

Peach Leaf Curl

Peach leaf curl is the most common and widespread disease of peaches. The disease is favored by the milder, wetter climate of Eastern Nebraska. Peach leaf curl is quite easy to recognize because of the curling and crinkling of the leaves as they unfold in the spring. Usually the entire leaf is affected, but sometimes only small areas of the leaf may be involved. In addition to the curling, diseased leaves are thickened and often turn red or purple.

As the season progresses, the diseased leaves turn gray and appear powdery. Eventually, the leaves turn yellow or brown and drop. This disease may also attack the fruit, blossoms and young twigs. Infected fruits seldom remain on the tree until harvest. Fortunately, peach leaf curl is one of the easiest fruit diseases to control. In most years leaf curl can be prevented effectively with a single application of Dexol's Ferbam, Natural Guard Bordeaux, or Ortho's Lime-Sulfur. Because infection occurs when the bud begins to swell, the fungicide must be applied during the dormant season. In Omaha this can be done in the fall, after the leaves have dropped, or in early spring before buds begin to swell. Temperatures should be at least 40 º Fahrenheit when spraying and remain above freezing for 12 hours afterwards.

Apple Scab

Apple scab is one of the most damaging diseases of apples in Nebraska. Scab is at its worst when humid, cool weather prevails during the spring months. The earliest evidence of scab appears on the underside of the leaves shortly after they emerge in the spring. The disease symptoms begin as faint olive-green spots somewhat darker than the normal leaf. The color darkens and the size of the spots increases with age. Later in the season the disease can be observed on both upper and lower leaf surfaces as well as on the fruit.

On apples infected fruit may be scabby, cracked, or misshapen. However, in most cases the damage is superficial and although unsightly, the edible portion of the fruit is not affected. Badly infected fruit may drop prematurely.

Jonathan and Yellow Delicious are fairly resistant to scab; however, Red Delicious and McIntosh are highly susceptible to the disease. When spraying these two susceptible varieties use a higher rate of fungicide for the first three cover sprays to ensure clean fruit. By following the Mulhall's Fruit Tree Spray Schedule, scar should be held under control. Stick to the schedule, a few applications could be a waste of effort and money. Infected leaves should be raked up and destroyed each fall.

Fireblight on Apples and Pears

Fireblight is a bacterial disease that is very difficult to prevent, but can be reduced by good sanitary practices and spraying properly with streptomycin (following package directions). Fireblight seems to be a serious problem on Jonathan, Rome Beauty, Wealthy, and Transparent apples. It is also a problem on Barlett, Clapp Favorite and Bosc pears. Other varieties are susceptible, but are generally not severely damaged.

Examine trees, especially susceptible varieties, once a week from blossoming time through July. If infected twigs are found, remove them by cutting infected portions off at least 6 inches below the visible infection. If removal is made with a knife or pruning shears, dip the blades in a solution of ½ cup household bleach to one gallon of water after each cut. Burn, bury or place diseased materials in refuse cans.

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