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<pre>It would be possible to determine both nematode levels and fungus infection
with appropriate tests. My preplanting assay for nemetodes indicated a
possible problem, and it had been pasture for 70 years.
In Victoria, Crop Health Services can analyse material
Peter Wilson

At 11:28 AM 7/18/00 +1000, you wrote:
>
>> 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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</pre>
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