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<pre>> From: Mohamed El-Kholy
>
> Dear Allan & Judith
>
> No your trees are definitely not dying. Further and based on the
> symptoms you have described (among which: leaves are turning black
> and falling off and stakes exhibit same oiliness appearance), I do
> not believe that you have a scale problem on those very specific
> trees. In fact they shall not be infected with scale for quite some
> time until they recover as they are currently drying out of their
> natural sap, which attracts such pests.
>
> You have been totally right. Increased oil concentration at the end
> of each 20 liters tank application has caused this and therefore if
> you look at your grove with a hawk eye, you will find the unhappy
> trees in distinctive spots. If your trees are similar in size meaning
> that they consume similar amounts of the spraying solution, you will
> even find that these spots have a symmetrical repeatable pattern
> (i.e. every certain number of trees). If you can memorize your
> spraying operation, you will ascertain that these trees were the last
> sprayed ones from each tank. For many different reasons and whatever
> growers are spraying, I always recommend that they should mark the
> last sprayed tree of each round with a ribbon for future assessment
> and data base establishment.
>

Mohamed,

I paid a visit to Judith's gove on the weekend, and your diagnosis is spot
on!

It seems that the oil and water separated towards the end of each pass of
spraying, so the least few trees took quite a heavy dose of oil. This is
causing the stickiness and dust is starting to stick to the oil. There is no
real damage to the trees, and the spraying was done late in the season after
the hot weather so there is no burning or "frying" of the leaves in the oil.

There does seem to be another, probably unrelated problem with a couple of
the trees, I suspect it is just a coincidence that thet were also oil
affected. My opinion is that there is some form of root disturbance causing
the trees to drop leaves. They are very young trees, to about 1.2m - 1.5m
and have kept the end of the branch leaves, but lost the leaves lower down
the branches. This is the same symptom I had with my Kalamata which turned
out to be a root fungus problem, so Judith will be spraying the trees with a
systemic fungicide (Alliette) next week to see if that clears it up.
It worked well on my trees about 18 months ago and they have recovered
fully.

>
> Oil affected trees do not easily surrender and die, unless they were
> originally unhealthy, and therefore they have sap traces in their
> drying out organs. To recover quickly they need your help. Prune them
> as per my last article of AOG issue 17 as I have already addressed
> this case. The degree of pruning will be proportional to the degree
> of oil and defoliation damage. The worst case might demand drastic
> pruning. After pruning and on the hope of removing some of the oil,
> which is choking them, wash them with a mild water jet, which should
> not cause more defoliation.

Much of the oil has now washed off, the only evidence is a darker, oily mark
on the trunk and on the stakes (plastic). We haven't had much rain recently,
so a wash would probably be a good idea.

My suspicion is that the oil they used wasn't misible. I have had no
problems using petroleum based white oil not "organic" vegetable oil. Alan &
Judith were advised by a local citrus grower not to bother with "expensive"
white oil and just use "organic" vegetable oil as it did the same job. I beg
to differ.

>
> Your more thinking and second diagnoses was right and this is a true
> example of new growers who have to be more self-confident and must
> trust their instincts.
>
> Prof. Stan Kailis of UWA has identified some of the causes for olive
> leaf loss and I would like to add two more to his list:
> Ø Ageing, which should be clearly identified by growers so that
> they do not get panic and ask for a remote advice over a distance,
> which might cause unnecessary harm. Here I am also giving an advice
> over a distance like many others, so please be cautious.
> Ø Draught.
>

Not aging ... trees are still very young and most of the grove is vigorous.
Probably not drought as the block is irrigated, however water stress might
be a factor.


> I might also add to Prof Kailis comments that nematodes cause leaf
> loss but do not cause defoliation. In this case the leaves will
> completely dry but will remain strongly attached to their branches.
>

Nematodes are unlikely as the ground is virgin territory and unlikely to
have built up any significant nematode population.



>
> TO UNSATISFIED OZ MANZANILLOS GROWERS: Again be patient and give your
> trees another chance for a season or two as I said before. I have
> been looking at oil yield figures of other cultivars from the same
> regions having problems with the Ms. Surprisingly none of them
> although purely oil varieties are yielding their promissed figures.
> In fact they are far behind! I am just wondering: are these varieties
> going to face same destiny? You need more time for appraisal
> researching!
> One thing I am sure of and that is (without hard feelings): Many
> growers who claim to have fully irrigated groves need to develop
> their practices of grove management as well as their targets.
>

This is very true. I am taking my irrigation schedule to fit in with my
vineyard irrigation schedule (I can't run both at once) and the vineyard
takes priority as the vines are a lot more finicky. I really should have a
good hard think about how much water and when.

Regards,

Mike Wilson
Twin Trees Cottages, Hunter Valley.
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