AMES, Iowa – Fall is almost here, and one of the best parts of the season is the apple harvest. Apples are a delicious, fun part of autumn, but care must be taken with harvest time, storage and potential blotches.
Iowa State University Extension and Outreach horticulturists can help answer questions about apples, storage and other issues.
When should I harvest my apples?
The harvest period for apples varies from one cultivar to another. For example, Jonathan apples are normally harvested in mid-September. The harvest season for Red Delicious apples is normally late September. However, the harvest time may vary by one or more weeks from year to year due to weather conditions during the growing season. Therefore, gardeners should base the harvest time on the maturity of the apples rather than a calendar date.
There are several indicators of apple maturity. Mature apples are firm, crisp, juicy, well-colored and have developed the characteristic flavor of the cultivar. Color alone is not a reliable indicator of maturity. Red Delicious apples, for example, often turn red before the fruit are mature. Fruit harvested too early are astringent, sour, starchy and poorly flavored. Apples harvested too late are soft and mushy.
When harvesting apples, pick and handle the fruit carefully to prevent unnecessary damage. Sort through the apples during harvest. Remove and promptly use bruised or cut apples. Discard apples that are seriously damaged or show signs of decay.
What are the proper storage conditions for apples?
The storage life of apples is largely dependent on the temperature and relative humidity during storage. Optimum storage conditions for apples are a temperature near 32 degrees Fahrenheit and a relative humidity between 90 and 95 percent. Apples stored at 32 F will keep two to three times longer than those stored at 45 to 50 degrees Fahrenheit. If the humidity during storage is low, apples will dehydrate and shrivel. When stored under optimum conditions, apple cultivars (such as Red Delicious) may be stored up to three to five months.
Small quantities of apples may be placed in perforated plastic bags and stored in the refrigerator. Perforated plastic bags maintain a high relative humidity, while they prevent the accumulation of excess moisture inside the bags.
Large quantities of apples can be stored in a second refrigerator, cellar, unheated outbuilding or garage. Place the apples in perforated plastic bags or plastic-lined boxes/crates. Apples should be moved from unheated outbuildings and garages prior to extremely cold weather as storage temperatures will likely drop well below freezing. Apples will freeze when temperatures drop below 30 F. Frozen apples deteriorate rapidly once thawed.
What are the black spots or blotches on my apples?
The problem may be sooty blotch and flyspeck, two different fungal diseases that often occur together on apples. Sooty blotch appears as dark brown to black, ½ inch or larger smudges on the surface of the apple. Flyspeck produces clusters of shiny, round, black dots. Individual dots are about the size of a pinhead. Environmental conditions that favor disease development are moderate temperatures and an extended wet period in late summer/early fall.
Sooty blotch and flyspeck live on the surface of the fruit. Damage is mainly cosmetic. The apples are still safe to eat. They’re just not very attractive.
Cultural practices and fungicides can help control sooty blotch and flyspeck. Proper pruning of apples trees and thinning of fruit promote drying and help reduce disease severity. Fungicides also may be necessary.
If control measures fail, sooty blotch and flyspeck can be removed with vigorous rubbing.