I've been working in a first serious garden this year and I'm coming to find out all of the things I don't know, especially when it comes to plant diseases. I think I've actually been causing more harm with what I do know, so I decided to bring it here, to the experts. Some of the relevant facts are that the garden is pretty small, so things are close to maximize space, it's usually partially shaded half the day and fully shaded in the evening, and with wood munch, it stays pretty wet, especially with the fairly consistent rain we've been getting here this year. I also foliar feed once a week with a mixture several organic fertilizers including Garrett Juice, Kelp, and molasses.
First up is a set of cherry trees, one rainier and one bing, pictures attached. The leaves started turning yellow about a month ago, first on one, then the other. Thinking it was a nutrient deficiency, I starting increasing foliar feeding them. Looking at them now, I'm pretty sure they both have leaf shot, meaning that wetting them down with lots of taste nutrients on a weekly basis was probably about the worst thing I could have done, I'm not sure if there is a leaf left that isn't effected. The effective treatments I've seen suggested are decidedly not organic. Does anyone have any suggestions? I'm currently debating adding them to list to spray with Potassium Bicarbonate with the squash and cucumbers (more on them later) and seeing if there's any improvement in the next month or just stripping and disposing of all the infected leaves, which would be almost all of them, and seeing if the ones that regrow have a fighting chance. Anyone who has some experience with leaf shot in cherry trees, I would appreciate any advice you have to share.
Next on the list would be the squash and zucchini with powdery mildew. I've been spraying them once a week with a solution of 2 tablespoons of Potassium Bicarbonate in 1 gallon of water. I know sodium bicarbonate is the usual recommendation, but from what I've been able to find, the Potassium is equally as effective and will be better for the soil in the long run. Recently, the mildew seems to be spreading faster and more prolifically. I wondering if I should up the strength of the solution or be spraying more frequently?
Also, looking at my cucumber plants, I'm pretty such they have a blight, as opposed to a nutrient deficiency. I've been spraying them once a week along with the squash and zucchini, but it doesn't seem to be having much effect. However, it may be slowing the spread as it seems to be spreading a slow, but consistent rate, but I don't have a lot of experience to know how fast it spreads untreated. Again, should I up the strength, spray more often, or is it just a limited effectiveness process?
Finally, should I be foliar feeding my fruit trees? Looking at the conditions leaf shot develops in, it would seem to asking for trouble with cherry tress. I also have apple, peach, pear, plum, and fig. Should any, all, or none of them be foliar fed? Again, any and all advice will be greatly appreciated.
Derek Callihan wrote:
Next on the list would be the squash and zucchini with powdery mildew.
Also, looking at my cucumber plants, I'm pretty such they have a blight, as opposed to a nutrient deficiency.
Can't recall for sure, but in a pinch you may want to use copper sulfate (Bordeaux Mixture) for the mildew, alternating it with applications you are currently doing.....I understand you may not want the copper in the soil in any large amount, but to get through this year might be okay.
The cucumbers may be getting mildew as well, but I might add to that the possibility of some insect feeding that transmitted a virus....by zooming in to the lower leaves in that photo, the ringspots are somewhat characteristic of *some* virus that may be common in your area. Bacterial wilt can start as well after insect feeding.
The good thing if you are just getting started is to try to squeak things through this year, take notes on your diseases in the even that you wish to find more resistant varieties in future years and, if you wish to start seed-saving, perhaps keep notes on which fruits/veggies came from the most healthy looking plants when saving seeds. If there is a Penn State or county extension office in your area that will diagnose horticulture diseases, it may be worth a visit to them for a positive ID. Good luck!
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Powdery mildew is a cup of skim milk in a gallon of water, spray on leaves in morning so leaves are dry by dark. Wet leaves late in day at this time of year usually get powdery mildew. Drip irrigate or otherwise avoid wetting leaves and also making sure of good air circulation and do not water within two hours of dark (sundown) helps. I fought this every year with my competition pumpkins, the milk works pretty well for them, and for roses too.
My first instinct is that you are spraying entirely too often and probably with spray that has too much bacterial/fungal food and not enough living beneficial bacteria/fungi. I have only seen spraying that heavily used on very high value crops in areas that are bone dry and very sunny. Potassium bicarbonate is a solid attack on powdery but I think that at this point the increase in humidity may do more damage than can be prevented by the potassium bicarbonate. You may want to look into switching to a biological predator of powdery like Bacillus Subtilis or Bacillus thuringienses (sp?) or another whose latin name I can't remember but that is sold under the trade name Actinovate among I'm sure others. My favorite product in this vein is called Companion because it has the Bacillus along with some humic acid. I would say spray no more than once every week and a half and spray after all sun is off the garden for the day. Another option, that is often cheaper, would be to make a aerated compost tea (takes less than 50$ in infrastructure but is a whole nother thing to add to your chores which is why I brought up the simpler options first) of worm castings, bokashi, and insect frass bubbled for 4-12 hours and then sprayed on at full strength also after light has passed for the day.
Mainly though, stop spraying so much, stop spraying food altogether and definitely stop spraying any molasses (in general I would avoid spraying molasses and only apply it to the soil and mostly as part of compost teas). Spray biology that can predate and displace the pathogens. You can add food to the soil (kelp, humates, fish, guanos, alfalfa meal) to feed the good biology there which will also help the plants immune system. And John said, do your best to stick it out this year and continue to observe and experiment, I would definitely say that the amount you are spraying is too much for your space. From what you say, I would spray no more than monthly in your garden, I would spray compost teas ideally but if not then I would spray things like kelp, yucca extract, fulvic acid, fish hydrolosate, and organic cal/mag/iron supplements. Really though I would focus your fertilizing energies on amending and liquid feeding into the soil, humidity is going to be your enemy in a shady garden in pitsburgh. Awesome garden though, looks good for a first garden to me and it will only get better.
Others have given great advice on what to spray or apply to the soil to effect a cure.
I do not spray, period, ever, the reason for this is that I live in a high humidity part of the planet and spraying only results in many issues.
If you are in a high humidity area and spray more than once every two weeks, you are spraying too often and you will increase powdery mildew and black spot fungus growth by doing so.
Plants need dry leaves to flourish, if you need to apply controls, try to find those that you can apply to the soil in dry form or wet the soil early in the morning.
Moisture on leaves will spot burn when the sun is magnified by the droplets on the leaves, which is not a good thing.
Since you have problems you can make mineral additions to the soil, including cupric sulfate and it will help with the mildew and other fungal issues.
Soil with proper mineral contents, proper biological activity and organisms is the best preventative and cure for any problems in any plants.
Healthy plants come from healthy soil, healthy soil will nurture the microorganisms your soil and plants need.
Tend the soil, don't treat the symptoms, that doesn't work for any living organism.
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Until you have boosted your soil with loads of organic matter and whatever trace elements it might be missing (and I believe you can do that by adding loads of different sorts of organic matter) spraying stuff on the top is not really very helpful. It's like beng a weedy person who goes to the gym after six months of doing nothing and just concentrates on working out their top half. Building your soil and taking a holistic approach will take time.
Acetylsalicylic acid is aspirin. This could be handy too: