I am a firm believer in Activated Compost Tea.
I have been using it for the last 3 years and it's great. I do not find caterpillars, aphids, in fact I have a shortage of any bugs.
Sprayed on peaches and nectarines will cure 'Peach Leaf curl' I just picked off any damaged leaves, then one wash down with ACT fixed it for the season. A plum tree with aphids, a good wash fixed them completely.
As a general spray or soil drench it does improve the overall growth patterns of all my plants. Google 'Activated Compost Tea' to get the full story.

Activated Compost Tea is promoted as one way to get a good healthy soil that will grow strong and healthy plants that will be better able to ward off attacks from insect pests and plant disease. ie. getting the amount of organic matter in the soil up to optimal. ACT does have fairly large numbers of the bacteria that soils need, but if your soil lacks sufficient levels of organic matter to support them they will not be able to function in the soil.
Take a good look at your soil and add enough organic matter to attain a 5 to 8 percent level, and work to keep the soils pH in a range of 6.2 to 6.8 with balanced nutrient levels.
To control insect pests until the soil gets into that good healthy condition may require using various control measures depending on the insect. A sharp water spray can be useful as can an insecticidal soap mixture. Dormant oil sprays can help as well as a clay spray that disguises the fruits from the insects. Stronger, broader spectrum poisons such as Neem oil and maybe the pyrethrins may be necesary sometimes. Keep in mind that plants and fruits with no insect damage are not normal and are acheived only with very potent poisons.

OK, sounds like getting the Californian worms was a good idea so as to speed up getting the quality soil levels. Looks like I need to find a pH meter.So much to learn - you guys opened another can of worms for me;)

Regarding the ACT or any other organic sprays/treatments - is there any preventive (ahead of problems) spraying I need to plan on / general frequency of doing this (I "try to grow" veggies, citrus, berries)?

Forgot to mention one problem I have - swiss chard/mangold - I always get some infestation from some insect (not sure what it is) - leaves black (partly looks like cob web) - any preventive or otherwise treatment that works (I usually get this spreading on all plants and good bye to crop) ?

There is mounting scientific evidence that the use of compost tea can help suppress some diseases and insects that affect plants.

When looking for real evidence on compost tea, or any other product that you have heard about don't forget that Google has a feature under the more button at the top called scholar. If you use this feature you can filter out the sales pitches and read the science.

Here is an overview of what I know and have learned about compost tea.

Compost tea is not a miracle cure for all diseases or pests. Evidence does show that it can suppress certain diseases, insects, even root nematodes and possibly within an acceptable level in some cases.

Most fungi infect plants when the leaves are very young and vulnerable so applying compost tea, or for that mater any chemical control, after the symptoms are seen is usually not going to give you any control.
Even if compost tea does not give you the desired control, it can do no harm and will supply your plants with nutrients.

Compost tea seems to work better the fresher it is.

There is still a great deal of research to be done on compost tea to determine how it works, on what, timing of application, production methods, how to keep it from loosing its potency over time, and a lot more.

By all means add compost tea to your arsenal of things you use to protect your plants under an integrated pest management approach, but don't expect it to cure all that ails. Remember that healthy plants can grow and produce fruit with a variety of diseases and insects, depending on the pest and the level of infestation.

There are also new organic fungicides such as Actinovate that use beneficial bacteria to control fungi that are showing promise, but the jury is still out on how good they are. Again do your Google scholar research on these.

Also Oil(Neem or Horticultural), Soap, Bt, and Spinosad, for insect control are all accepted as organic.