In 2012, we are in the 'on' phase of the alternate bearing cycle; consequently, we are expecting (and hoping for) a heavy crop load. A heavy crop load, however, does not come without consequences. A high fruit load will result in reduced vegetative growth during 2012 and exacerbate the degree of alternate bearing in the following 'off' year. Production of a large crop of small fruit may impact profit. Management of fruit size may be achieved by pruning and/or chemical thinning.

Why Thin Your Olives?

Larger fruit. Overloaded trees bear small, unprofitable fruit. If a crop is thinned during the fruit’s early growing period, the remaining fruit will grow larger. The larger fruit command a higher price that more than offsets any reduction in total yield. By thinning the crop, you will bring otherwise substandard-sized olives up to canning sizes. Additionally, recent studies suggest that larger fruit are more compatible with mechanical harvest techniques—a consideration for growers intending to try mechanical harvest in the future.

More consistent yearly crops. Maintaining a modest crop size from year to year may mitigate the extremes within the alternate bearing cycle for olive.

Early maturity. A moderate crop matures earlier than a heavy crop. An early crop is more likely to get a good reception from the handler, has less competition for harvest labor, is less likely to fall victim to cold weather in the early fall, and ensures a good bloom for the next year.

Lower harvest costs. Olive picking costs are figured on a per-ton basis, so the per-acre harvest costs for a moderate crop are less than for a large crop.

(For more, see: Ripe olives boost California economy almost $500 million yearly)

Pruning vs. Chemical Thinning

Pruning removes potential fruit and foliage but does not change the leaf-to-fruit ratio. Shoot growth is stimulated, which will help minimize alternate bearing. Chemical thinning is achieved with use of the plant growth regulator, naphthaleneacetic acid (NAA). NAA is absorbed into the leaves and fruit and is then translocated to the fruit stems. An abscission layer forms during the first two weeks after NAA application, causing some fruit to drop. Only fruit are removed, and the leaf-to-fruit ratio is changed. Therefore, chemical thinning is potentially more effective in mitigating the effects of alternate bearing than pruning. Pruning plus chemical thinning is recommended for crop control in 'Manzanillo'; however, chemical thinning is not recommended for 'Sevillano'.