Lh Forsythe

yet another video, this time from Advancing Eco Agriculture, 'Why Plant Disease Increases Before Harvest'
https://youtu.be/dAPhmxCOqqQ

mainly on auxin / cytokinin balance, but touches on senescence briefly. Ethylene is the senescence hormone produced in fruit.

my comments: do you really want to decrease auxin / cytokinin ratio in fruiting plants since auxin (according to video) moves sugars into fruit? Would you be trading pest resistance for taste/fruit quality?
Overall I find AEA video series interesting, but would prefer more review of scientific evidence; anecdotes (like the example of mites in corn) are interesting but scientific studies are needed.

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Papers I've skimmed say that cucurbitacin is anti-insect, but that some pests have evolved resistance & even use it to deter their own would-be predators. That dang evolution thing again.
Hydrogen sulfide is an anti-senescence signalling molecule in plants & is associated with cucurbitacin production, so there goes all my idea on cucurbitacin as being somehow related to senescence in plants (but it is in cancer cells, go figure).
https://pubmed.ncbi.nlm.nih.gov/30707394/

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Article on using Chlorella supernatant (the leftover culture medium from growing Chlorella) to delay senescence:
https://www.tandfonline.com/doi/pdf/10.1080/15592324.2020.1763005?needAccess=true
my comments: main constituent is lactic acid, could be obtained from other sources. LA is a reducing agent and it is possible other reducing agents would also work.

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So there is a literature base on plant senescence in relation to crop yields, but many use term 'leaf senescence'. So leaves will senescence in annuals as they do seasonally in perennials, but in annuals I expect there is also root senescence. Perhaps root senescence is main driver in annuals & that's why auxin / cytokinin balance is so important?

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Anyway, I continue to read up on the topic as time allows. If anyone has any links to good podcasts/videos please post as I am able to listen/watch as I do chores - my time for reading literature is limited, unfortunately.

Another video, this time from James Prigioni on increasing cucumber yields:
https://youtu.be/Q7Pg5MYJZKM

He points out a few things of interest relating to senescence in cucurbits. One is well-known - if you want to prolong production you need to harvest fruits while they are immature. There must be a signal from the mature fruit to the main plant that triggers senescence. He says cucurbitacin is a bitter compound that attracts cucumber beetles & big, overly mature cucumbers are bitter - so perhaps cucurbitacin is the signal. Interesting the bugs like the bitter compound; often the bitter compounds are phytoalexins. Perhaps the cucurbitacin  is the beetle's cue that plant is senescing & therefore has lower leaf Brix? (but I have still have not confirmed whether my assumption  about leaf Brix & senescence is correct)

Did a search & found out that cucurbitacin triggers senescence in colon cancer cells - how's that for cross-kingdom signalling!
https://pubs.acs.org/doi/abs/10.1021/acs.jafc.1c07952

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sort of unrelated - Prigioni also says it's the cucurbitacin that causes some people to burp when they eat cucumber so I'm wondering if it also somehow affects carbonic anhydrase (enzyme for CO2/bicarbonate interconversion) activity.

I watched this video by a home gardener on squash vine borer & zucchini.


What really grabbed my attention was that one of his four zucchini plants was not senescing whereas the other three were (and one of those was rapidly succumbing to SVB).

Presumably leaf Brix declines with plant senescence (does it?) & delaying senescence would increase yield & pest resistance.

Why was senescence delayed in that one zucchini plant?

I finally sent in a query to our Extension service with pictures. I'm concerned this may be Grazon contamination. I don't think  I want to eat anything from my garden anymore. The Dow statement on Grazon contamination says you can eat the produce, but not sell it. That's not reassuring.

When I think of reducing agents the first thing that comes to mind is vitamin C. While I get that the goal is to have healthy soil that oscillates between being a reducing environment and an oxidizing one, foliar feeding of minerals was discussed in the video as a temporary fix for nutrient availability issues due to soil being overly oxidizing.

But what if you just watered in an ascorbic acid / potassium ascorbate solution (adjusted to appropriate pH)? Seems like that might be easier and cheaper than foliar feeding with minerals. *

Has this been studied?

* I'm not against foliar feeding with minerals, in fact I really like the idea - though as yet I've no direct experience (tomorrow I will try it myself for treating blossom end rot). I have suggested to the void of Twitter (no responses, no likes) foliar feeding of rice with molybdenum to try to reduce arsenic uptake into the grain. Don't know if it would work but it would be great if it did since in people with controlled Celiac (on GF diet, low tTG IgA titre), whole grain consumption is associated with an increase in neutrophil to lymphocyte ratio (N:L), meaning higher levels of inflammation.  This is opposite of what one would expect; I think it is likely the culprit is higher arsenic intake from whole grain rice since the GF diet tends to be high in rice if it contains grains at all (some opt for low carb or just eat tubers and fruits to be safe). High N:L is associated with poor health outcomes (& maybe not so coincidentally has to do with redox imbalance); lowering arsenic levels in rice would benefit the whole population.

The first plant that had a problem was the tomato I bought from Home Depot (I bought because I was unsure of my starts). Could I have imported it? I hope not.

You're right, John, curly top is not supposed to be here & there is nothing on our extension office's website about it. So that would be a strong indicator that I messed up ... again.
{ I took out 2 peppers and a tomato! }

It could be sodium stress (soil test said high sodium in the mostly compost raised bed) - but all the other plants in the RB are fine.

The pepper in the pot on the patio is doing great & it's in mostly compost from the same company (I have to buy since I only got started this year), plus some coir.

Also don't know what to make of the peas being so stunted and deformed - it looks like pics of BCTV. They are not in the raised bed.

I have spotted a leaf hopper, but that doesn't mean much.

I will contact the extension office.

I jinxed myself ...

Yesterday it got up to 101° F, one kabocha wilted and now the fruit it had on its longest vine are caput.  So I will start foliar feeding as soon as I can figure out how to get my new hand pump spray thing-y to unlock. If squash are like tomatoes, then according to the article, the feeding should also increase vitamin C and possibly carotenoid content ( in tomatoes it increased lycopene, but squash don't make lycopene).

The study author included some detergent as a wetting agent so I will add a few drops of dishwashing liquid to the solution. He only fed 2x, I guess I will try doing it once a week. IDK, many sources say foliar feeding does not work. Should be interesting.

I'm pretty sure this is not a lack of pollination issue since it looks like a wasp spring break beach party in the blossoms.

Is it possible the kabocha will produce more female flowers along that vine or will new production just be from the growing tip on? If it's the latter, should I just cut the vine as it's getting super long & unruly?

Anyone have tips for managing heat stress in humid areas? Should I be putting up some shade cloth at mid-day? Like I mentioned, I am watering deeply now with watering can at the base of the plants in the AM so as to try to not get things mildew-y.  

This study tested the effect of 10 mM and 15 mM solutions of CaCl2 for foliar feeding on blossom end rot in tomatoes; 15 mM seems very effective.

https://www.researchgate.net/profile/Mohamed-Ibrahim-41/post/Does-anyone-know-how-to-treat-a-calcium-chloride-to-plant-leaves/attachment/59d61ef979197b807797d5f8/AS%3A271780598251528%401441808952965/download/4.pdf

The molecular weight of CaCl2 is ~ 111 g, so 111 g/mol

15 millimoles = 111 g/mol * 15/1000 = 1.67 g

So 1.67 g CaCl2 / L water

There are 3.785 L / US  gallon -  6.3 g CaCl2 g per gallon would be needed to make a 15mM solution - which seems a lot less that 4 tablespoons.

Unless I made an error, which is quite possible.

In any case, the new fruit seems okay since I started watering more deeply, so I probably don't need to do this anyway.

Thanks!