<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>Here's a description and control pf Peacock Spot from California. So far,
Copper is OK for organic growers here.

Olive Leaf Spot

Olive leaf spot, peacock spot, and bird's eye spot are names for the disease
caused by the fungus Spilocea oleaginea (Cast.) Hughes. Worldwide, it is
known as olive leaf spot; in California, it usually is referred to as
peacock spot. The disease occurs in all olive-growing regions of the state.
Cultivars vary in susceptibility, but all are subject to infection.
Outbreaks are sporadic, and the disease may take several years to become
serious enough to cause alarm.


Symptoms. Leaves, fruit, and fruit stems may be attacked, but lesions are
observed most often on the upper leaf surfaces. Lesions first appear as
small sooty blotches 1/16 to 1/4 inch (2 to 6 mm) across; these later become
muddy green to black spots (color plate 18.2). Some lesions develop a yellow
halo and remind people of the "eye" spot on a peacock's tail feathers;
hence, the vernacular names peacock spot and bird's eye spot. Many lesions
may occur on a leaf. Most infected leaves fall prematurely, which weakens
and kills small wood and eventually reduces productivity. New infections
are first seen in late winter and early spring; by summer, most affected
leaves have fallen, leaving partially defoliated shoots with healthy leaves
on the tree. The disease is usually most severe in the tree's lower part
and north side. Old lesions become crusty and whitish and seldom produce
many conidia.


Disease cycle. Not all infected leaves fall, and the fungus survives on
those that remain in the tree. These holdover lesions produce very few
conidia during summer, and in fall, the lesion margins expand and a new crop
of conidia is produced. In Spain, young leaves were found to be very
susceptible in spring. Many young leaves infected in spring remained
symptomless until fall when they became the main sources of inoculum through
autumn and winter.
The conidia are picked up and spread by moving water, which is why the lower
parts of trees are most commonly infected. Lateral spread is very limited
and even adjacent trees may exhibit vastly different amounts of disease.
Conidia germinate only in the presence of free moisture, and germination,
infection, and mycelial growth proceed readily over a wide range of
temperatures, 70oF (21oC) being optimal. Most infections take hold during
the coldest part of California winters; temperatures above 86oF (30oC)
restrict germination of the spores. Infections established in winter take
longer to become visible as lesions than do those initiated in spring.
Inoculum buildup appears to play a major role in the severity of olive leaf
spot. It may take several years for this disease to cause economic loss.


Control. Olive leaf spot is controlled by a copper-containing fungicide
applied once in late fall before winter rains begin. A second application
is of questionable value; if used, it must be applied before mid-January.
Later treatments, as recommended for olive knot, offer no protection against
olive leaf spot.

Steve Sibbett
U.C. Farm Advisor Emeritus
Phones:
Office: 559.734.4607
FAX: 559.734.2708
Mobile: 559.280.0666
e-mail: sibbett@lightspeed.net



-----Original Message-----
From: Stan Kailis [mailto:kailis@ca.com.au]
Sent: Wednesday, October 03, 2001 12:49 PM
To: OliveOil@yahoogroups.com
Subject: Re: [OliveOil] Peacock Spot


Dear all

The procedure should be

Ç Harvest
Ç Prune
Ç Apply copper sprays

All these are done between late autumn ans Winter, well before the
evolution of flower buds.

Regarding Boron - remember that with any nutrients added to soil to
check soil pH. Nutrients can be present but unavailable to the plant
because of pH or lack of water.

Stan Kailis



-----------------------------------------------------------------
Inviting others to join this group is simple: Just ask them to
send an empty message to: OliveOil-subscribe@yahoogroups.com
-----------------------------------------------------------------
For more information: http://groups.yahoo.com/group/OliveOil
Post message: OliveOil@yahoogroups.com
Subscribe: OliveOil-subscribe@yahoogroups.com
Unsubscribe: OliveOil-unsubscribe@yahoogroups.com
List owner: OliveOil-owner@yahoogroups.com
------------------------------------------------------------------

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/





[Non-text portions of this message have been removed]
</pre>
</td></tr></table>