This week we discuss another new technique we are using this season to reduce our disease pressure. But first a few announcements.
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Farm News
Last week I discussed the “results” of our attempt to reduce pathogen pressure by heat treating our seeds prior to planting. The goal was to reduce or eliminate some of the diseases that may be on or in the seed itself. Seeds are one of the primary disease vectors in growing veggies. The other disease vectors are soil, air/wind and finally pests — typically insects. This week I’ll discuss some things we are doing to reduce diseases from both air and soil this season.
So first lets talk about the pathogen vector wind, or more specifically plant to plant transmission, which could be due to wind but could also be due to workers brushing up against an infected plant then subsequently brushing up against a non-infected plant thus creating a newly infected plant. Heat treating won’t help with this problem as you can imagine. Trying to stuff a large tomato plant into a cauldron of hot water isn’t feasible. Plus we’d probably just end up with tomato soup, and not in a good way. So we have to approach it with another technique.
But first, this might be a good time to mention that all of the techniques we use are only effective for certain plants and certain diseases. In other words, we can’t eliminate all seed borne diseases from all seeds by heat treating all seeds. For example, squash seeds are too big to heat treat. It’s not that they can’t fit into the water tanks but that the seed itself is too big to heat through without destroying the seed. So heat treating doesn’t work for large seeded crops. There are also some seed borne diseases that don’t succumb to heat treating. Therefore, even though we are doing certain techniques to reduce diseases, we are not eliminating that particular disease vector (e.g. seed borne diseases) for all the plants we grow and all the diseases they have. We are just solving a small problem for one or at most a few of the plants we grow. Considering how many types of plants we grow and how many diseases each of the plants has you can understand how complicated and difficult disease management in a diverse vegetable operation can be! It kind of explains why other farmers just spray toxic chemicals.
Now back to our plant to plant transmission solution. In our case the particular pathogen we are trying to reduce or eliminate is leaf mold in our hoop house tomatoes. Leaf mold is caused by the fungus Passalora fulva. It primarily affects hoop house tomatoes due to the higher relative humidity found there; we typically don’t see it on field grown tomatoes but that could be due to the field grown tomatoes being overwhelmed by many other diseases before the leaf mold has a chance.
They (who are these they?) say leaf mold doesn’t reduce the yield of the tomato plant but in my experience it does reduce the leaf cover and negatively affects the life of the plant. Plus, reduced leaf cover can result in more sun scald and cracking so why not find a solution? This season we are trialing a few leaf mold resistant tomato cultivars, specifically Bigdena, Geronimo and GinFiz — the last being a bicolored tomato variety. Plants that are “resistant” to diseases are just that, resistant. They can still get the disease but they tend to have lesser infections and fewer issues, kind of like those who get vaccinated for COVID being resistant to COVID but can still get COVID — unless of course they are on a prophylactic dose of ivermectin, in which case they will probably still get COVID but not botfly larvae. (I wonder if Facebook will flag this newsletter for having COVID related information like it did this other newsletter from a while ago?)
Anyway, the seeds for these leaf mold resistant tomatoes are significantly more expensive than more traditional varieties like Big Beef but if they produce more and have superior fruit they will be worth the extra cost. How much more expensive? Well, they’re around $1 per seed. Doesn’t sound like much but we grow somewhere around 500 tomato plants. Just to give you an example of a non-leaf mold resistant variety, Big Beef is more like $0.05 per seed. For the math challenged among us I’ll tell you the disease resistant tomatoes seeds are 20x more expensive.
I know what you non-math challenged are thinking, “Do the new varieties have to grow 20x more tomatoes to be cost effective? Isn’t that how the math works? Doesn’t seem reasonable that you’re going to make your money back Farmer Chris!” Well, there are a lot more factors that go into the growing of tomatoes equation than just the cost of the seed. Though using these new varieties will be more expensive, the overall cost of production shouldn’t be 20x the cost of production of the other varieties. Cross your fingers that we do much better with the new varieties. And if not we just go back to growing the cheap Big Beef tomatoes from our past. That’s why we call it a trial.
What about all the heirlooms you grow. Are they going away? Of course not. We will continue to grow those as well — both inside and outside — so you can count on them still being around this season. We were just looking for a more disease resistant ordinary red round tomato that may perform better than our traditional round red tomato. But the mention of heirlooms brings us to the second experiment we are doing this year to reduce diseases. And in my opinion this is the more exciting “experiment” — tomato grafting.
What is tomato grafting? It is how we humans try to play God (or maybe Dr. Frankenstein) by taking the top half of one plant — the scion — and attaching it to the stem and roots of another plant — the root stock. The scion is of the tomato variety we want to harvest, say Eva’s Purple Ball or Green Zebra. The root stock is a tomato variety that is resistant to soil borne diseases but does not produce marketable fruit. By using a disease resistant root stock grafted to a desirable tomato variety we hopefully reduce or eliminate those soil borne diseases in our tomato plants yet still have the delicious tomatoes we’ve come to enjoy over the years. Take that Dr. Frankenstein!
Additionally, not only does the root stock reduce the transmission of the pathogen from the soil into the plant but it can also be superior to the plant’s native root stock in providing nutrients to the plant. It’s like having a larger diameter straw to drink your delicious beverage, but for plants and roots. This increased nutrient flow results in more tomatoes from the same plant/space. Of course for us to do this grafting we have to grow twice as many seedlings — an equal number of scion and root stock plants — and then take the time to graft them together. The root stock seeds are expensive (about $0.40 a piece) but if they increase our yields it will be worth the extra cost and effort.
So, my hope is by using scions from plants more resistance to wind blown pathogens (the approach mentioned first) grafted to root stocks with resistance to soil borne pathogens (the second approach) we get a plant that is resistant to many of the pathogens we see in the tomato growing business. We will also experiment with grafting some of the heirloom plants to the root stock to see if we get superior heirloom fruits with fewer disease problems. I’m also thinking of a few small experiments to see if we can use this same grafting approach to overcome other plant maladies like blossom end rot in peppers. I have not found any research on this so maybe it is an area we should be investigating. If our preliminary trials look promising we might apply for a grant to get money for a more extensive trial in 2023.
Other plants like watermelons, cucumbers, eggplant, etc. can be grafted as well however research isn’t as extensive for these plants and the commercially available root stocks aren’t as easy to come by but we may look into doing something along these areas in future years.
One thing I should point out is that all of these strategies do not use any pesticides — organic or not. How swell is that? Fewer pesticides to harm unintended targets. So using these strategies with all the other strategies we hope we can become even more environmentally friendly.
Well that’s enough words for now. Let me know if you have any questions, comments, suggestions, brain teasers, etc. I’m always up for answering questions that interest our members rather than just spouting off on whatever idea might pop into my head, which by the way is running out of things to spout off about so send in your questions! And now for this newsletter’s joke.
What did the baby corn say to the mama corn?
Where’s popcorn?