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damping off/seed sowing notes

There has been much discussion about damping off lately.

Here are a few notes (by and large taken from a hort paper 
assignment I had cause to do a couple of years back) based on my 
experiences and reading. They are basic, tried and true. I hope they 
will assist. If you wish to add or refute please do so.There were 
originally graphics to go with this but they got lost on a currupt 
floppy (it took a bribe and fled). I shall also transfer this to our 
home page

Some notes on Seed Sowing and Damping Off

Damping off is a problem that many amateurs, and too many 
professionals,  tend not to handle very well, probably because they
don't understand what they are dealing with.
Damping Off is a generic term for all those diseases which kill the 
new seedling upon, or shortly after emergence, and is usually
caused by either or all of the following pathogens:- phytophthera,
pythium or rhizoctonia sp.

 These three vandals often work in concert and are 
all "water moulds". That is they live in and are transported by
water. They are thus easily transported from one place to another by
water splashes, in soil, on equipment etc. and will readily carry over
from seed trays used last time, or last season, unless these are
treated in some way that kills them. I find the easiest way to do this
is to wash (plastic) or soak (wooden) flats with "Jey's" fluid
(directions on the bottle). This kills the pathogens, is cheap, easy
to do and safe to both plants and humans. Do the same to benches that
you place your flats on and, if you really want to be good, scrub the
adjacent walls and floors.

 It is also a good idea to cover your bench, which should be high
enough to prevent water splashes from the ground, with new, thin (30 -
50 micron) black plastic. The mulch plastic you may be able to obtain
from garden centres is ideal. This provides a protective barrier
against any disease still left below. (water moulds can "swim" up into
your flats).

 Ok, so now you have a clean bench and tray (flat) so don't go
contaminating it with unclean soil, mix or equipment (hands
included). After I have my trays and mix and seed ready I *always*
wash my hands, just in case, before handling the seed.

 Water with clean water. Avoid using water collected from the roof and
taken from a barrel at the bottom of your downpipe. Using this water
(without first boiling it) may give you warm fuzzies as a
conservationist but it will also re-introduce disease. Chlorinated
house water is ok

So the first step is "Hygiene". The second step is "Hygiene", as is
the third. This is very important and well worth the time it takes.
Any compromise will have results which will have to be dealt with
later. 

I will of course deal with these.....later

More notes on seed sowing/disease etc.

Having prepared your propagation room, which is of course in a
place which allows maximum light and is well vented (to prevent
disease and high temperatures) and sanitised as above, you may as well
sow the seed.

Seed Mix

Whatever mix you use to sow your seed in it should retain moisture
while being well aerated and pathogen free. Some seed sowing mixes
available "off the shelf" are none of these. You will have your own
pet mixes but a 60/40 peat/pumice ratio suits very well  John Innes
mixes or UC (University of California) soiless mixes are great. Above
all, avoid mixes that waterlog easily

Sowing

Sow the seed thinly. Sowing too thickly encourages damping off
diseases in the young seedlings by preventing good aeration and
allowing moisture to spread disease. Don't cover seed too deeply
and thickly. It is common to see the whole surface of the mix in
the flat raise up as seeds germinate. This is called
bridging...thought you might like to know. If this happens water
heavily to break the bridge and allow to dry off again

Water

Moisture is critical. If seeds dry out after absorbing water they may
die. Too much moisture may suffocate seedlings and encourage root
rots. Watering must be uniform but not excessive and above
all....avoid watering in the evenings when excess moisture does not
dry off.

Temperature

Air and media temperature should generally be in the range..15-25
degrees centigrade (60-75deg F). Unthermostatted heat beds may cause
excessive heating, as will unshaded, glass covered flats. This will
kill seed or induce secondary dormancy. Cooler temperatures may
inhibit germination. Soil temperatures in flats may frequently be 4-7
degrees F below air temperatures due to evaporation

Pests

Ants, mice, slugs, cicadas, fungus gnats, lizards (?) can cause major 
damage. Take whatever measures you are comfortable with to rid 
yourself of these pests.

Seed Viability

Is the seed fresh? Some seeds go off (not with a bang..although
some do) quickly, eg.delphinium. If you chill your seed a week
before sowing it could well result in a more even and reliable
germination. Check for special requirements, temp, stratification
etc.. Some seeds are not compatible with certain fungicides eg. Thiram
suppresses germination and stunts seedlings of nemesia, phlox
drummondi and others. Take care to read the directions on the
fungicide ...and seed..packets


All Right. I'm getting there. So you've got "damping off" and want a
quick fix NOW

Put trays in a light, well aired (but not draughty) area. Water
thoroughly with "Previcur N" (propamocarb) "Terrazole"
(etridiazole/xylene) against pythium and phytophthera, and/or
"Rizolex" (tolclofos-methyl) against rhizactonia { check the
chemical names, in brackets on the fungicide packets, if the trade
names, in parentheses, are not in your store} or try chamomile
tea...it may work.

Terry
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Terry Dowdeswell
Tuakau, New Zealand
Terry@delphinium.co.nz
~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://www.delphinium.co.nz
~~~~~~~~~~~~~~~~~~~~~
Time flies like the wind - fruit flies like bananas
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