Fungal spores usually show up in a garden via the wind or insects. One
of the most common are those which cause leaf spot diseases such as
early blight. Tomatoes are highly prone to this type of fungal spore and
can get infected without you even knowing it. Dark brown patches on the
leaves of your tomato plants means they have early blight, which spreads
fast on damp leaves. this is probably mistaken for burnt leaves...

At the first sign of early blight, it is advised to clip off infected
leaves, but only if the foliage is dry. Messing around with damp,
infected foliage will only serve to spread millions of fungal spores
throughout the garden and infect other tomato plants. After infected
foliage is removed (if possible) it is advised to spray down the tomato
plants with a mixture of one part milk to four parts water, along with 1
teaspoon of baking soda for every quart of water used. A few drops of
liquid soap will help to make the spray stick. The reason this spray is
effective is that dried milk when exposed to the Sun's ray's temporarily
changes into a disinfectant, while the bicarbonate component of baking
soda kills new fungal colonies.

Jonno wrote:
Here's a link and part of a theory, which backs up what I read.

http://cahe.nmsu.edu/ces/yard/1999/062899.html

But wait I think there's more...

Jonno wrote:
The water on the leaves story has been around for some time, and been
investigated. The problem is really caused by fungal infections due to
water on the leaves. The sun does not magnify due to different focal
lenght. But plants can suffer from straight out sunburn....Tomatoes
for instance get sunscald.

I'll try and find the story again if I can...

I wonder is some plants are susceptible to the pyrethrum?


Blackadder IIVX wrote:
"Jonno" wrote in message
u...
Maybe you burnt them due to the gas being a sort of refrigerant. In
other words youre spraying a bit too close to the plants.
Do it when there is no winf ie early in the morning when theres very
little wind. Then you can spray them with some distance in between.

Oh no. I use the hand pump manual add ons. I don't use a spray can.

Its just the heat of the sun. Even if you just spray cold water on
the plants- the sun magnifies the droplets and burns the plant.