I've been gone from the recent discussions due to other work, a number of
trips, and an occasional holiday. I note, in my absence, one subscriber's
reference to several weaknesses of California’s "Olive Production Manual".
As one of the editors, I thought some clarification in order.

First (and probably foremost), the University of California’s "Olive
Production Manual" was developed as a practical grower guide for table olive
culture in CALIFORNIA. Although much of the information in the manual
pertains to, and is useful for olives and their culture in general,
including elsewhere, the specifics, based on the five table olive CVs we
grow, were written for the California industry (99.9% of the California
industry is devoted to table olives) based on experimental (not
experiential) data developed here - so, by default, this is a table olive
production manual; in California it doesn't have to be specified as such.

One should not assume that all of the information contained in the manual
pertains to worldwide conditions or, especially the "oil" component of the
world industry. Due to the predominance of the table olive industry in
California, olive oil information is, by design limited in the manual,
albeit the information that does exist has an experimental data-base
developed in California for foundation. A revision of the manual containing
substantially more information for California olive growers (including more
on oil) is currently in progress and it is hoped the 2nd edition will be
ready by early summer (California summer) 2001.

The pollination component of the manual was criticized. I note comments
directed toward the manual such as "The totally misleading statement that
olives are mostly self fertile is repeated again and again as one author
copies the mistakes of the last" or "pollination is poorly covered". First,
I do not find the statement "olives are mostly self- fertile" anywhere in
the manual let alone being repeated "again and again as one author copies
the mistakes of the last". Those comments are simply untrue and reflect
naivety of what information the Olive Production Manual contains. Indeed,
the implicated need for cross-pollination is referenced on pg 35 "pollinizer
placement" and again on pg 54 "factors that reduce fruit set". Secondly, in
response to the statement that "pollination is poorly covered", there is
some truth to this. However, one needs to realize our industry is a table
olive industry. In California, table olive growers are paid based on fruit
size. Excessive crops result in small, low value fruit (sometimes worthless)
that don’t recover harvesting costs and poor cropping can be expected the
following year. The Manzanillo CV (predominant CV grown for table olives
here) has been estimated to produce upwards of 500,000 flowers here. One to
two percent fruit-set results in 3-4 short tons per acre (7.5 – 10 short
tons/ha) – crops exceeding this may have a predominance of small, low value
late maturing fruit forcing the trees to alternate bear. The California
literature often shows up to 2% fruit set of Manzanillo when
self-pollinated; indeed in California there are many examples of blocks of
single CV (Manzanillo) olive trees with a history of profitable table olive
production in areas where only Manzanillos are grown. Note however that the
University of California recommends either inclusion of a compatible
pollinizer CV with Manzanillo (i.e. Sevillano or Barouni - Mission and
Ascolano are not compatible with Manzanillo and vice versa) or provision for
application of supplemental pollen if needed based upon the grove’s past
history. The Olive Production Manual briefly discusses this on pg. 35 and
more pollination information will be added in the revised edition based on
the more recent California work of Cuevas and Polito in ’97 verifying the
work of Sibbett in ‘92. We recommend about 2 pollinizer trees per acre
(based on Griggs, et al work on pollen dissemination) – remember, Manzanillo
is the only CV we want to grow so we are not often interested in solid rows
of another CV.

Several references on olive pollination have been published relating
research done here with the California Manzanillo that we rely upon for
recommendation:

1. Cuevas, J. and V. S. Polito, 1997. COMPATIBILITY RELATIONSHIPS IN
"MANZANILLO" OLIVE. HortScience, Vol. 32(6), October.

2. Sibbett, S., V.S. Polito, L. Ferguson, 1992. EFFECT OF TOPICALLY APPLIED
"SEVILLANO" POLLEN ON NORMAL SEEDED AND PARTHENOCARPIC “SHOTBERRY” FRUIT SET
OF "MANZANILLO" OLIVE. HortTechnology 2:228-230.

3. Griggs, W.H., H.T. Hartmann, M.V. Bradley, B.T. Iwakiri, and J.E.
Whisler, 1975. OLIVE POLLINATION IN CALIFORNIA. California Agricultural
Experiment Station bulletin 869.

4. Bradley, M.V., W.H. Griggs, and H.T. Hartmann, 1961. POLLINATION OF
OLIVES UNDER VARYING TEMPERATURE CONDITIONS. California Agriculture, March.

Many of the pollination questions raised in this forum have been researched
for the CVs grown for table fruit in California and are referenced in these
papers (e.g. distance pollen moves; role of bees; CV cross compatibility,
etc.). In general, there is universal agreement that olive fruit set is
improved with cross pollination – California is no exception as we generally
recommend pollinizers for the California Manzanillo. However, as California
is an example, local experience and experiment should prevail and guide
recommendation.

Steve Sibbett
U.C. Farm Advisor
Phone - office 559.733.6486
Mobil 559.280.0666
FAX 559.734.2708