Hello all.this is my first attempt at posting. We have a 2500 tree grove in Western Australia, close to the ocean. The oldest trees were planted in 2001. Although large and vigourous, many of them have terrible scale infestations so that the current fruit is either sticky with honeydew, or dirty with sooty mould. The scale seem to breed continuously. I spray with white oil mixed with a little Potassium carbonate, but am not having any noticable success in getting on top of the problem. We have natural predators in the grove, like lady bird beetles and predatory wasps, but they aren't winning either. Any suggestions would be gratefully received. Regards, Judith Williams

Hello Judith,

Scale is very hard to tackle, because the scale protects the insects from contact insecticides. Generally they're relatively well controlled by the natural predators , but in your case they're obviously not doing they're job. This is probably due to your spraying.

There is one very effective strategy in controlling these insects, one should wait until the beginning of spring when the younger scalelees insects of the new generation start to move. This is when they're vulnerable to contact insecticides like the ones you've used.
So you are left with two options:

* if your growing the olive organically, you will have to wait for the next spring, there is no point in doing anything now;

* if not, you can treat the plants with conventional insecticides, the best are: Methidathion, Phosmet or Carbaryl (these are the names of the active substances, you will search for the commercial names).

Cheers,

João

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João Correia
Cascais - Portugal
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msn: jorgegranja@yahoo.co.uk

skype: JoaoJCorreia

Hi Judith,
In my experience, the timing of spraying is critical. I use only white oil with 750g/100l of sodium bicarbonate and have had quite bad infestations of black scale. In the last couple of years, I have gained much better control by examining the scale under a microscope before I spray.

There's no point in spraying the adults as the oil can't penetrate their hard shell, which protects the eggs. You need to get them at the crawler stage to have much effect. If you turn the adult scale over, under a miscoscope or magnifying field glass, you should be able to see the coral-coloured eggs. If you tap the adults on to a white sheet of paper, the eggs will show up against the white background, without the aid of magnification.

Hold off your spraying until most of the eggs have hatched, leaving behind the fluffy white remains of their shells under the adult shell. You then have a period of a week or two in which to target the crawlers. You will have to repeat this exercise 2 or 3 times over the season. This year, the eggs were very slow to hatch, probably due to our mild start to summer in WA, so I saved a lot of time and money by waiting. I look on my purchase of a basic stereo microscope as one of my best investments yet. Apart from the obvious benefit, it's very interesting to look at the insects under good magnification.
At the very least, get yourself a good field eyeglass and carry it with you whenever you're in the grove.

I hope this is of some help.
Regards,
Julie

We too have had an ongoing battle with scale in the Southern Tablelands NSW. We have used Eco Oil from Organic Crop Protectants with concentrated Garlic and Pybo (Pyrethrum) which seemed to be effective. However diligence is the key factor. You can only have success getting them in the wriggler stage so several sprays spaced about 2 weeks apart in sep/oct, dec/jan and feb/march could be necessary. We thought we had beaten the buggers this year but got a late outbreak in april. It's an onerous task which I think we will have forever. You can't beat them only minimalise them. Good luck.

Thank you all for your replies. I guess I just have to keep spraying when the crawlers are visible (which in my case seems to be throughout the year in one area of the grove or another). I recently tried to buy some metaphycus wasps, but none were available, and I have ordered some cryptolaemus beetles, which are a type of ladybird, normally used for meally bug control, but they also consume scale crawlers. I was wondering if anyone had used them, and if so, with what success? Regards, Judith Williams

You could always try the "non-chemical" route. I have used ant deterrent tape on some of my trees. It stops the ants from getting into the trees to "farm" the scale insects. That reduces the effect of the sooty mould and a small amount of scale can be put up with.
I have a contact for Aust readers, but will not post here. PM me if you want details.

I have also just started using ant trap material in "semi-liquid" form and will be happy to discuss the results of this with people if they ask. (Give it a while to have an effect, though!).
Cheers
John
Tamworth NSW Au

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"I spent most of my money on booze, women and fast cars, the rest I wasted" George Best (arguably one of the best footballers ever!) R I P

A friend from around here found that the ladybirds went elsewhere after release. Presumably there were better meals provided in the neighbour's paddock.

Don't know of anyone with a ladybird fence??

Cheers
John Attwood
Tamworth NSW Au

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"I spent most of my money on booze, women and fast cars, the rest I wasted" George Best (arguably one of the best footballers ever!) R I P

As I said in my previous post, probably the only period of the year when one can effectively reduce the population of black scale is early spring, when there aren't any adult alive and all the population consists of the young, them you should treat when the crawlers are visible.
(I'm presuming you are in a part of Australia where there is a period of the year you can call winter, when the plant and insect growth stops.)

Cheers

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João Correia
Cascais - Portugal
____________________________________________
msn: jorgegranja@yahoo.co.uk

skype: JoaoJCorreia

I wish the scale only bred in spring. Because of our mild climate and high humidity being near the coast, I seem to have hatchings all through the year. It is winter now in Western Australia, and fresh eggs are still appearing. I have been spraying for months and am no closer to getting control. Are you aware if sooty mould is detectable in the oil from dirty fruit? Regards, judith

Hello Judith,

You should pay attention to the spraying, it might be the cause of your problem.
Contact insecticides aren't very effective against black scale, but their very effective with the black scale predators, like the lady bug. So, at the end, you might be helping out the scale by eliminating its predators.
These type of uncontrollable infestations generally appear only where the predators populations are very reduce due to constant spraying.

As for the sooty mold, I confess that i do not know if it will transmit any flavors to the olive oil. But my educated guess is that it probably will be some substance that is liposoluble and will end up in the oil, giving it some strange flavor.
Also pay attention not to spray to close to the harvest, because you're using an oil based insecticide that will most definitely end up in the olive oil.

Good luck fighting the black scale,
Cheers,

__________________
João Correia
Cascais - Portugal
____________________________________________
msn: jorgegranja@yahoo.co.uk

skype: JoaoJCorreia