Generally when we talk about problems in a vegetable garden we're talking about pests
and diseases, and weeds of course. For the most part we have weeding under control in most of
the growing spaces that we manage as part of this RED Gardens project, or at least the weeds never
get to the point where they start to impact the yield or health of the vegetable plants.
But that hasn't always been the case and I still fail occasionally with some of the explorations
that we do. We have a range of different pests that can cause problems, but we're gradually
getting better at finding ways to eliminate them, or to reduce the damage that they do,
or at least keep them away from the crops. Some pests we've had better success than others.
But diseases are still an issue for me, especially the fungal diseases,
and I haven't been great at paying enough attention and giving consistent focus in
managing them, and often I just end up letting the diseases run their course.
This year I decided to make more consistent efforts to use a milk spray to reduce the impact
of powdery mildew on the leaves of courgette or zucchini plants, especially later in the season.
This spray seemed to be more effective than I expected, but I'm still not sure if this is
something that I will consistently use as a main way for dealing with this common plant disease.
Courgette or zucchini plants can produce a lot, sometimes too much,
and we're often quite glad when the harvests start to slow down towards the end of the season.
I do put in the effort to look after these plants, especially earlier in the season to protect them
from frost and the cold winds, and I really look forward to the first few harvests. But the amount
of attention that I give these plants tends to reduce as the season progresses, and because I
grow quite a few plants there tends to always be enough even if I don't put in the effort. I have
been doing more to care for these plants in recent years especially trying to provide enough water
and fertility for continual growth, but apparently I haven't been so successful with that in some
cases. I occasionally do some hand pollination, especially when I don't think there's enough bees
around to do the job earlier in the spring. I removed some of the side shoots and prune out
a lot of the older leaves to reduce overcrowding in the beds, and to prune out some of the leaves
that are worst affected by powdery mildew. I have tried using a milk spray a few times in the past
few years to deal with powdery mildew infections, which is a method that I've seen recommended a few
times, but I haven't used it consistently enough to be able to determine if it's really effective.
Powdery mildew is a fungal disease that is spread through spores and can apparently affect quite a
few food crops and other plants, but I've mainly seen it on squash, courgettes and
cucumbers which are all closely related plants. This disease has also infected some pea plants,
including a really bad infection with one batch of peas this season. The spores develop
into fungal growths or colonies on the surface of the leaves and other parts of the plants,
which looks like a white powder or dusting, hence the name. And this has the result of blocking
photosynthesis as well as extracting nutrients from the leaves themselves. The more of the plant
that is infected the greater the disruption or restriction and growth of the plant there will be,
which of course leads to reduction in the yield or productivity. As with many fungal diseases
and plants, there is a lot that can be done including growing healthier plants, and reducing
overcrowding, and pruning to remove any affected leaves, and cleaning up any plant debris as well
as general garden hygiene in order to reduce the chance of spread or reinfection. There are some
fungicides that I could buy in to use as a control but generally I try to stay away from those types
of solutions. Over the past couple of years I've seen a number of recommendations to spray the
leaves of infected plants with dilute milk as an alternative form of controlling powdery mildew.
Apparently sunlight reacts with the proteins in the milk to create antiseptic compounds which
last long enough to damage the fungal infection on the leaves. But then these compounds degrade
into something more benign, so the leaves need to be sprayed on a regular basis to
restrict reinfection, and apparently it's better to use it as a preventative spray.
This year the plants in the outside gardens were infected with powdery mildew by mid-august, or the
infection started earlier but mid-august was when I noticed and started to do something about it.
I started by pruning out the older leaves of the plants, removing a lot of the leaves that
are worst affected by powdery mildew, and giving more space for the remaining leaves.
I then mixed some milk with about twice as much water, and used this to spray the leaves,
concentrating mostly on the parts of the plant that still had signs of fungal infection. I
use skim milk which still has the proteins which are apparently the essential element
but doesn't have any of the cream, as I wasn't sure if I wanted to cover the leaves with butter
fats if it wasn't useful. I tried to spray on a sunny day as that is what is generally advised,
and when the forecast indicated that there wouldn't be any rain for a day or two. But
that can be tough here in Ireland, especially with the overcast and rainy summer that we just had,
but I ended up being able to spray these plants four times, approximately 10 days apart.
We were also growing courgettes in one of the polytunnels, as part of an experiment in
relay cropping, where these plants would produce courgettes later in the season. And they started
to get infected with powdery mildew at about the same time in mid-august, but they were younger
plants so they were infected before they needed the first pruning. Rainfall was not an issue
in the polytunnel of course, so I had a little bit more flexibility as to when I could spray,
but I wasn't sure how much sunlight was needed and if direct sunlight was essential.
These courgette plants are partially shaded by taller plants, and I'm not sure if the plastic
would affect the nature of the sunlight, and if the spray would be effective at all. I ended up
spraying these plants with the dilute milk every six or seven days, concentrating most of the spray
on the leaves that were obviously affected, but also spraying the overall plants including
the leaves that showed no signs of powdery mildew. I was thinking that this could be a
preventative spray, damaging the initial growth of the fungal colonies before they were even visible.
There were definite improvements to the plants in the polytunnels, as the leaves that had been
affected were now dull, not powdery as before, and I assumed that this is the remains of the
fungal colonies that had died off. And the infection didn't seem to spread as much,
but it's hard to tell as I didn't leave any plants unsprayed as a control. But at least
a lot of the younger leaves seem to remain unaffected for longer. There were still some
leaves with powdery mildew, especially the older leaves lower in the plant, where there would have
been more time for the fungal colonies to develop. But they're also more likely to be shaded and it's
possible that not enough sunlight was able to hit the leaves in order to change the proteins
and the milk into the antiseptic compounds. I cut off and removed most of these leaves,
as part of the regular pruning that I was doing in order to keep these plants more under control,
to prevent overcrowding in this polytunnel. At this moment late, in the season, there are
very few leaves on these plants with any sign of powdery mildew. It could be that the conditions
are not good for the spread of this fungal disease, but it seems that the milk spray worked.
The courgette plants in the outside gardens also seem to be doing better because of the milk spray,
but again I don't really know because I didn't leave a few unsprayed as a control.
It probably would have been better to start spraying these plants earlier,
before the infection really took hold, as I had done in the polytunnel. Not only to
reduce the drain on the plants, but to prevent the production of more spores to spread the infection.
As it was later in the season, with the weather cooling down, and these plants getting older,
and there being additional issues including some nutrient deficiencies in some of the plants, it's
hard to say how much of an impact this spraying with dilute milk would have had on these plants.
But the spray does seem to work well enough both outside, and in the polytunnel, to use as a method
for controlling powdery mildew infections in the future. But I don't think it's necessarily the
only method, or perhaps even the main method to reduce the impact of this fungal disease.
It is interesting that not all of the courgette plants in the outside gardens were affected by
powdery mildew, even though it was the same batch of plants, from the same variety, and the same set
of seeds, all transplanted at the same time into four different gardens. The plants in three of the
gardens were affected by powdery mildew, but one plant at the end of the row in two of the gardens
didn't seem to be affected at all. I'm not sure why this had happened, but it might be because
some of the roots of the courgette plans had grown in amongst the potato plants in the adjacent bed.
And as we harvested the potato plants, digging out the potatoes, this would have damaged some
of these roots, perhaps making the courgette plants more susceptible to powdery mildew.
And the courgette plants at the end of the row would have been affected later on in the season,
perhaps allowing them to be more resistant to the first round of powdery mildew infection. Also the
four courgette plants that were spread out in the polyculture garden were completely unaffected by
powdery mildew, right up to the end of the season. These were big strong plants, that were growing
really well with lots of space, because I hadn't got around to planting the succession crops that
would have filled in the other parts of this bed. It could be this extra space and lack of
competition, or that the soil around these plants wasn't dug, so there wouldn't have been any root
damage, or it could have been better fertility, or some other factor that protected these plants.
It could be that the plants were bigger and stronger because they didn't have to suffer
through the powdery mildew infection, but I think that the fact that they were strong
and healthy was part of the reason that they didn't get infected in the first place. I'm
not sure but it shows that infection by powdery mildew is not inevitable for courgette plants.
I was wondering if the wind direction could be a factor, that the spores being blown by
the wind could miss some of the plants. And this could make sense because the courgette plants in
the polyculture garden were generally upwind from the other infected plants. But with two batches of
late season peas that we grew this year, the opposite was true, with the batch of peas in
the Intensive Garden being badly affected, and the batch in the No-Dig Garden which was downwind were
not affected by powdery mildew at all. Given that these two batches of plants were only 10 meters
away, and sown from the same variety, and the same seeds, at the same time, I suspect that it
is some difference in soil condition or fertility availability that has led to this difference in
susceptibility to powdery mildew. But there is not necessarily anything inherently better in this
particular management method, as a few years ago the peas and the No-Dig Garden were much
worse affected by powdery mildew than any of the other peas in any of the other Gardens that year.
There are other factors of course, including the different varieties of the same vegetable can be
more or less susceptible to powdery mildew. I have seen this with different varieties of
squash and pumpkins that we grew this year with some varieties being really hit back by powdery
mildew but the leaves of other varieties right beside them were not affected at all.
So a spray of dilute milk definitely seems to be an option for reducing the impact of an infection
of powdery mildew, at least on courgette plants. But I think I'd rather figure out how to grow them
so that they are naturally resistant to this type of fungal disease. Part of this could be selecting
a different variety, giving the plants more space and making sure that there is adequate fertility
and water, and not damaging the roots, but this is not necessarily possible, especially if I want
to grow a lot of vegetables in a relatively small space. So it's really nice to know that I can use
a milk spray to knock back any infection that does occur. There is a cost in using milk spray like
this, both in the cost of the milk itself, and the time that it takes to spray the plants and clean
the sprayer afterwards. And this cost and effort increases if I'm going to be more proactive with
spraying as a preventative measure, especially if I'm spraying a wider diversity of crops in
all of the different gardens. But I think there could be a real benefit in spraying earlier,
as this would reduce the amount of spores that are created and spread across other parts of the
gardens, and reduce the amount of spraying that is needed later in the season. And it will be
really interesting to see what difference it'll make to the yield of the courgette,
peas and squash plants, if I'm successful at using this spray to prevent the spread
of this fungal disease. But this preventative spraying is another thing to remember to do,
rather than simply respond or react whenever I see an infection of a powdery mildew. And it's
another task to add to a long list at a busy time of the year, and a fair amount of milk to
buy perhaps there is a balance in all of this, to accept a certain amount of powdery mildew
infection in the gardens, especially when it can serve as a useful indication of when conditions
might not be optimal for the different plants. To indicate when things might be able to be improved.
Having the capacity to do those important things, at an appropriate time, is a big part of how you
can be successful with a vegetable garden, and it's also a big part of how you can be
successful with a YouTube channel. People who have been watching this channel for
a long time will have noticed that I haven't been uploading videos as often as I used to,
but this is something that I'm definitely going to change as we head into the winter,
where I plan to upload much more frequently, as we have more time away from the gardens. I also
haven't been doing many of these little things at the end of the videos, where I talk about the
channel, and ask for subscribers and supporters on Patreon, but those are also important things
to do on a regular basis. All of the work and explorations that we do in the RED Gardens
project, and all of these videos that I make, are funded almost entirely by ad revenue and Patreon
supporters through this YouTube channel. So, if you like the work that we do, and you value
the videos that I make, it'd be great if you could do what you can to support the channel,
either through liking and sharing this video, subscribing to the channel if you haven't already,
and also perhaps considering, if you have the capacity, to support this project even further
through Patreon or PayPal, the links to both are in the description below. I really want to
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as without you this project would not exist. And I also want to thank everybody for watching.