Cherry fruit doubling and spurs are caused by adverse environmental conditions the previous growing season.

Identification

Fruit is doubled when two fruit are fused together and share a single stem. When only one of the fused fruits grows to a mature size, the fruit remaining immature and undersized is called a spur.

Disorder Development

Fruit doubling and spurs are a result of poor flower development, or pistil doubling. The cause is excessive tree stress the previous growing season, commonly high temperatures during mid- to late summer and possibly water stress. Doubling or spurs the following growing season are commonly induced during the 4 to 6 weeks after harvest because this is when flower bud (pistil primordia) differentiation occurs, the time when immature reproductive tissue separates into individual fruit buds.

Damage

Fruit spurs are unappetizing but are easy to remove by hand before eating the attached, ripe fruit. Doubling and spurs can make fruit more susceptible to decay, such as during storage. Some varieties are more susceptible to doubling and spurs than others. For example, Bing, Early Burlat, Royal Ann, and Van have a high doubling potential. Growing locations where temperatures exceed 100°F during late July to early September are most likely to produce doubling and spurs of cherry fruit. However, a week of temperatures in the high 90s°F or higher during late June can acclimate the buds to heat so that high temperatures later are less likely to induce fruit doubling or spurs.

Solutions

Provide trees with good growing conditions and proper cultural care so they grow vigorously and experience less stress. Appropriate irrigation is especially important.

References

Adapted from Doubling Potential of Sweet Cherry Cultivars, California Agriculture, University of California.