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<pre>Dear friends.
I have a traditional plantation of olive trees (Picual variety) in Andalusia
(Spain).
From three years ago a few trees have verticillium (leaves on one or more
branches, often on only one side of the tree, turned yellow and/or wilt).
I often read your discussions and I realize you know a lot of olive tree.
Do anyone know how I could combat this plague?.
Thank you very much.
Regards.
Esteban Enrique Moya Morales
emoya@wanadoo.es
http://perso.wanadoo.es/emoya


[Non-text portions of this message have been removed]
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<pre>Esteban:

We have considerable VERTICILLIUM Wilt (VW) problems with olives here in
California. There is no known cure (eradicant) for problems in established
trees - we simply remove dead portions of the tree once the damage has "run
its course" (mid-summer)- we "live with it". Here are some comments you
might find useful based on our experience followed by what we publish for
pre-plant control:

1) I feel VW here has to infect the tree each year - note, some suggest it
survives in infected trees in the roots although we have no data to support
that. Others (& I) feel it has to infect the tree each year, so, simply
because you see symptoms one year does not necessarily mean you will see
symptoms the next (this type of damage is our experience here which does not
support the root survival theory).

2) There are several strains of the VW fungus. Some are quite severe and
some that only cause minor, small wood damage. Strains that infect cotton
here are the most serious while those that infect tomato are less so. If you
are only seeing small branches dying, you probably have a less severe
strain - note, you should have a local pathologist look at this for you to
be sure its VW.

3) Here, Sevillano (Gordal) is the most sensitive to VW (it can kill large
trees). Manzanillo is also quite sensitive but rarely does it kill the
entire tree - it will kill a limb one year then maybe 2-3 years later kill
another, depending on the strain present (the damaged area re-grows in the
meantime). You may wish to investigate the sensitivity of Picual to
determine degree of future problems you might experience and how to manage
it.

4) As mentioned, there is no control for infected trees. Prune to remove
damage when dying has finished.

5) here are our recommendations for pre-plant methods of controlling VW

OLIVE
VERTICILLIUM WILT
Pathogen: VERTICILLIUM DAHLIAE

SYMPTOMS:
The leaves on one or more branches suddenly wilt early in the growing
season, and this process intensifies as the season progresses. Death of
mature trees infected with VERTICILLIUM is possible. Darkening of xylem
tissue, a key symptom for distinguishing VERTICILLIUM wilt in many crops, is
frequently not apparent in olives.


COMMENTS ON THE DISEASE:
The fungus survives from season to season in the soil and probably in the
roots of infected trees. In early summer the fungus can be readily isolated
from diseased tissue in infected trees - but not later in the season.


COMMENTS ON CONTROL:
When replanting in an area where susceptible perennials were previously
grown, remove as many roots of the trees or vines as possible.


Soil Solarization. Beginning in late spring cover the surface of an entire
block with transparent plastic that has a UV-inhibitor additive. Leave the
plastic on throughout the summer and as long as practical. Inferior plastic
will break down and render the treatment ineffective. Solarization gives
inconsistent results when used in replant spots.


Soil Fumigation. Dry soil by withholding water during summer and using cover
crops not susceptible to VERTICILLIUM wilt such as sudangrass. The drier the
soil, the better for deep penetration of methyl bromide. Deep-till the area
after drying. If the soil is dusty, wait for an early rain before ripping
and fumigating. Ripping a dry soil that is silty can result in large clods
on the surface. Inject methyl bromide 18 to 30 inches deep with chisels and
cover with gas-proof cover. Increasing the dose tends to increase the depth
of penetration, but it cannot be relied upon to penetrate wet soils,
especially if soils are high in clay. Do not remove the cover for at least 2
weeks and aerate 1 month before planting. Treatments may be made from late
summer to early fall. In tree crops, methyl bromide often gives inconsistent
control.


TREATMENT:

Pesticide Amount to Use
(commercial name)
----------------------------------------------------------------------------

Preplant
A. METHYL BROMIDE/CHLOROPICRIN* Label rates
COMMENTS: See notes above.

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

-----Original Message-----
From: Esteban E. Moya Morales [mailto:emoya@wanadoo.es]
Sent: Sunday, July 30, 2000 7:51 AM
To: OliveOil@egroups.com
Subject: [OliveOil] VERTICILLIUM DAHLIAE


Dear friends.
I have a traditional plantation of olive trees (Picual variety) in Andalusia
(Spain).
From three years ago a few trees have verticillium (leaves on one or more
branches, often on only one side of the tree, turned yellow and/or wilt).
I often read your discussions and I realize you know a lot of olive tree.
Do anyone know how I could combat this plague?.
Thank you very much.
Regards.
Esteban Enrique Moya Morales
emoya@wanadoo.es
http://perso.wanadoo.es/emoya


[Non-text portions of this message have been removed]




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