I have Dyna Gro pure neem oil. I mix a little bit of it in a spray bottle with a drop of dish soap and spray regularly to control pests and fungal problems. I also sprayed my transplants when I first got them and experienced no problems. Not sure if the solution you have has additional stuff in it that could be problematic. I had a brief period during a rain spell with what appeared to be bacterial specking on a couple of plants, but either the plants simply outgrew it, or the neem helped to keep it under control. The biggest obstacle for me so far has been battling the spider mites (they come in from leaves off a neighbors tree that are loaded with the mites, daily), so it's very hard for me to really get rid of them completely. So far, though, my neem applications seem to have been very helpful in terms of fungal problems (last year and the year before I had much more problems with my in ground plants in terms of blight, and I planted the tomatoes in the same spots this year because it's the only spots I have). This year, they are big and green. Not sure if I'll make it the whole season with such good luck, but I've been attributing it to the neem oil.

At what point is it recommended to start preventive neem treatment?

The fungicide is your personal choice but the recommendation for ALL fungicides, if prevention is the goal, is from day 1 of plant out and per the label directions thereafter.

Once the fungus is on the leaf surface then it becomes a matter of 'control', not 'prevention'.

Dave

I use the Dyna-Gro Neem as well, and I spray my transplants in the late afternoon/early evening on the day of transplant, once they are out of direct sunlight.

Like Dave said, you should spray from day 1 to prevent fungus from setting in. The only caveat is that I would do it in the evening to prevent any potential leaf damage from the direct sunlight heating up the neem oil and mildly burining the leaves. By the morning, the oil will have absorbed into the leaves, or the excess will have dried up and your plant should be fine.

Neem oil is pretty mild, and shouldn't harm transplants anyway, even though the directions say to wait for root formation.

Hope that helps,

Mihcael

You don't want to bother with all this spraying of neem etc, it is by far easier and better acting if you obtain some Neem seed meal fertilizer and incorporate this into your tomato beds and compost, it is systemic in it's action and works all season long until about three weeks before harvest time, and is the best method I have ever come across, it keeps off all manner of aphids, white flies,and other insects, and also deters slugs and snails to a certain extent.

If you dig and rake in some of the Neem seed meal roughly about a couple of weeks before you plant out your tomato plants, you will never have any bother from aphids and other bugs again.

The fertilizer does have some feed value in the fact that it is around 6% nitrogen and other elements to give a nice balanced amount to start off with,and is made in India from the waste by-product of crushed neem seeds from which they extract the neem oil, and is readily available at several places in the USA and the UK and several other countries where they sell it in six to ten pound bags,- marvelous stuff :)