Archives for posts with tag: plant diseases

Since mid-summer, I’ve been spraying the cucurbit leaves with a baking soda and peroxide solution on a more or less weekly basis (see July 12, 2014). Why? To ward off powdery mildew.

I’ve tried other approaches such as pruning the affected leaves and spraying with diluted milk. The first method was futile (too little too late). The efficacy of the second method was difficult to assess (I was using pasteurized milk, not raw). Perhaps the progress was slowed but, in the end, the plants were overcome.

The baking soda solution, on the other hand, seems to be working very well. The first signs of powdery mildew did not appear until very late (the end of August) and the spread has been slow. The mildew has been limited to a small fraction of the leaves.

Unfortunately, the spray is not completely effective. Powdery mildew is still present and, eventually, it can still have a detrimental effect. The cucumbers are more susceptible but the summer squash have suffered a bit, too.

Also unfortunate is the fact that the spray does nothing to prevent bacterial wilt. We have had fewer cucumber beetles this year (who knows why?) but clearly they’ve given our cukes the kiss (well, bite) of death.

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Warning: Insect photo below.

We’ve been pretty good about keeping the tomato plants pruned this year. It’s a difficult balance between over-pruning, which can reduce a vine’s productivity, and under-pruning, which can lead to disease and insect infestation.

We’ve also been vigilant in our checks for hornworms, who like to hide amongst the tomato leaves—sparse, dense, or otherwise—silently munching away at them until suddenly (it seems), the branches are bare.

And up until today, we haven’t found any. I don’t know if this is due to our efforts or it is just a bad year for hawkmoths. Either way, I’m happy to have survived most of the summer without having to deal with them and hope I don’t see many more.

Oops. Spoke too soon.

Shhh, don’t talk too loudly or they’ll hear.

(We haven’t had any striped cucumber beetles or hornworms this year…yet.)

My second least favorite garden activity: Digging holes in our rocky, clayey soil. (Long-time readers of this blog know what my least favorite garden activity is; new readers can look at January 7, 2012 for a clue.) Unpleasant as it is, I have to face up to it if I want to be ready in time to plant summer squash and cucumbers over the Memorial Day weekend. More specifically, I need to start digging if I want to plant them in a different place from last year.

And I do want to plant them in a different place. Most gardening experts advise rotating crop locations every year. Moving vegetables in the same family around the garden helps protect them from insects and diseases that can hunker down in the winter and lie in wait for the new season’s plantings. Given our problems with cucumber beetles, aphids, bacterial wilt and powdery mildew, it is worth the effort.

Many sources advise a four-year rotation. Because crop rotation also helps balance demands on the soil (heavy feeders one year, light feeders the next), the suggested schedule sometimes includes a season of so-called green manure (peas, buckwheat, winter rye, alfalfa) to replenish nutrients or a cover crop to stifle weeds. I love the concept even if we cannot afford to lose any planter space to vegetables we do not plan to eat.

Any separation of the rotating groups is beneficial but to be maximally effective, there should be as much distance as possible between the individual planting areas. I’ve seen recommendations of up to a quarter-mile. That sounds good for large-scale growers but a quarter of a mile from my garden is practically in the next county. We’re very limited by the space available to us.

So we do the best we can. We have two raised planters and each year we alternate what goes into them. Last year, we planted cucumbers behind the west planter; this year, we will move the cukes to a similar location behind the east planter. And after laying out a dozen mounds for squash, we only dug and planted half of them last year, in a staggered arrangement. This time around, we’ll plant the other six. The separation is not huge but it’s not zero, either.

Which leads me back to the digging. It’s not my favorite activity but when it is done, the garden will be in a better state (and I shouldn’t have to do it again next year).

I’m still going through the process of evaluating last year’s plantings to determine what will go into the garden this year.  Last time (see January 15, 2014), I used three criteria:  how much we liked the vegetable; how well it grew; and, if not well, what could be done about it.  So far, I have concluded that all of the cucurbits—summer and winter squashes; cucumbers—are loved, grew reasonably well (with exceptions) and can be encouraged to grow better.

What else did we grow?  Well, lots of root vegetables.  And, I should point out, lots of root vegetable greens.  The radishes, carrots, beets and turnips all sprouted quickly and then produced a full crop of verdant leaves.  This was not at all a bad thing because I have come to enjoy the greens almost more than the roots that generate them.  Whether plucked from the garden early (as part of the thinning process) and thrown into a salad or clipped from the mature roots and sautéed, they are a delicious addition to the table.

Sadly, the roots took a lot longer to develop, if they did at all, and their eventual success was varied.  The radishes did particularly poorly with the first and second plantings yielding a root only about half of the time while the third planting never really reached maturity.  The carrots and beets performed moderately better but were painfully slow (especially the carrots) to ripen.  I don’t think any of them got as big as they could have.  The turnips were the top performers and provided both sizeable roots and plentiful greens through most of the summer.

I think we’ll give them all another chance this year (we still have plenty of seeds) but will make sure to limit their Nitrogen, by which I mean that I will not add any to the soil.  That means using fertilizers that do not contain it (i.e., those with zero as the first number in their N-P-K rating).  I will have to do some research into what might work best but that’s a topic for a future post.

I would prefer to limit the colors of the radishes and the carrots because we found that the purple varieties were the tastiest (I guess I like the flavor of anthocyanins; see October 20, 2013), followed by the red.  However, that would be difficult without buying new seed.  Our current radish and carrot seeds are “rainbow” mixtures and there is no way to determine the root color from the seed’s appearance.  I suppose this is one good reason not to buy seed mixes.

Five of the six tomato varieties we planted last year passed the taste test and for the most part, all of them performed well.  We’ll replant the Country Taste Beefsteak, the Brandywine (although, perhaps, only the yellow), the Black Cherry, and the ever-popular Sungold but we’ll skip the Aunt Ruby’s German Green.  Therefore, we’ll have room for some new varieties.

And speaking of room, I think we will give each tomato plant a bit more this year.  Pruning remains a critical factor for tomato plants and the lack of space (due to the vines’ exuberant growth) compounds the issue.  The first year we gardened, we pruned too little; the next year, we pruned too much.  We’d hoped that last year would be just right and, in the beginning of the season, it was.  But then, at the peak of the summer, the tomatoes’ rapid growth overwhelmed us.

This year, we’ll plant one tomato seedling per cage and keep a closer eye on them.  Each plant will have more space to spread into and will have less impact on its neighbors.  With luck and careful pruning, each vine will remain within the confines of its own cage and will wrap around it rather than spill over the top.

Keeping the tomato plants separate will be also important to prevent the spread of blight which, having made an unwelcome appearance last year, is likely to return this year.  Once it arrived (on the Brandywine or Black Cherry vines), the blight quickly spread to the other plants.

The only vines that did not contract the disease were the Country Taste Beefsteak, which is another reason to replant them.  Even though the beefsteaks were infected by some other disorder (Septoria leaf spot?), it did not really affect their output.  Spraying everything with a bicarbonate of soda solution should also help.

I’m happy to report that the 2014 growing season is officially under way.

In our garden, anyway.  Having assembled all of the necessary parts, I found some time this afternoon to sow seeds for the herbs.

As a first step, I washed the mixing tub, seed tray and trowel with a mild bleach solution.  All of these items were used last year and have been stored in the basement since.  The exposure to outside elements is high and given the dark and damp conditions down here, the potential for mold and harmful bacteria is great.

Then, I mixed up a batch of seed starting medium.  I measured out quantities of peat moss, vermiculite and perlite (in a 2:1:1 ratio) to equal a half gallon of dry volume and dumped them into the tub.  The lime I purchased is pelletized so I used a mortar and pestle to pulverize it into smaller particles.  A quarter teaspoon per gallon—an eighth of a teaspoon for this batch—seemed much too small; I used a teaspoon.  To be more accurate, I would need to know the pH I was starting with.

Using a spray bottle, I moistened the mix and stirred it with the trowel.  Peat moss is extremely dry and perlite can absorb a lot of water so I had to repeat this process for several cycles.  When the moisture content seemed right—damp but not soggy—I spooned the mix into a half seed tray (that’s 36 compartments) and tamped it in lightly.  It turns out that half a gallon of seed starting mix is just the right amount.

Next came the seeds.  We will be planting basil again this year (last year’s did extremely well) along with the herbs we purchased seeds for last year but never managed to plant:  rosemary, thyme, oregano, spearmint and sage.  Because most herb seeds are very small, I used tweezers to drop one or two seeds into a shallow hole (formed using a pencil as a dibble) in each compartment.

After covering the seeds with a pinch of mix (the recommended sowing depth for herbs is only 1/4 to 1/2 of an inch), I gently sprayed the tray with water until it ran out of the bottom.  For most of the herbs, this will be the only water they get until they germinate and emerge from the soil 10 days (or, in the case of the rosemary, 28 days) from now.  I set the covered tray atop a heating pad on a shelf of the seed starting apparatus, turned on the pad and fluorescent light and made sure that the timer was properly set.

Like all seed sowing, starting the herbs is an act of faith.  This is especially true for the oregano and spearmint whose seeds are teeny-tiny (they are packaged in small zip-top plastic bags within their paper seed packet).  I can’t be sure whether any seeds actually made it into the soil or from which tray compartments they will sprout.

But I firmly believe that they will and I will be thrilled when they do.

At breakfast last Saturday morning (pancakes and eggs at our favorite local joint), we started in on early planning for this year’s garden.  The first thing we concluded is that we are not really early.  By some reckonings, we should have sowed seeds for thyme last month and could be starting other herbs right now.  The second thing we concluded is that, once again, we are behind schedule.

Luckily, the choices of what to plant this year were relatively easy decisions even though a fair amount of thought went into each one.  We started with the list of plants we grew last year and then applied a few different criteria to assess their success.

The most important criterion for each vegetable is our answer to the question, did we like it?  It doesn’t matter how well it grew or how much it produced if, at the end of the day, we won’t eat it.  Of last year’s crops—those that actually yielded fruit—the only one that did not absolutely thrill us was the Aunt Ruby’s German Green tomatoes.  They were not bad, per se, but they didn’t leave us wanting for more.  Consequently, we will not grow them again this year.

There was one plant whose fruit we could not taste.  The Delicata winter squash did set fruit—several of them—but was not able to develop any of them to maturity.  And that leads to the next criterion, performance.  Plants that did not thrive last year may not be suited to our particular microclimate.  Then again, we may not have given them what they needed, either.

So, what besides the Delicata did not perform?  Well, the Kabocha winter squash produced only one specimen by the end of the year and it was a small one at that.  That’s two strikes against the winter squashes and based on this meager showing, I was tempted to say that we should try other varieties this year or skip them altogether.

However, roasted with a little olive oil and salt, the Kabocha squash was absolutely delicious.  It passed the first criteria with flying colors even though it showed weakly on the second.  Similarly, although we were not able to sample the produce of our Delicata, it is one of my favorite varieties (we often buy it at the farmers’ market).  Therefore, we will try the Delicata and Kabocha squashes again.

The next criterion then is, why did these vegetables underperform?  My best guess is that we underfed them.  I haven’t reported on last year’s testing yet (look for a future posting) but soil properties are a definite suspect.  The areas we planted with the squash were newly formed last year and have not had much chance to stabilize.  This spring, we will probably need to enrich their soil and fertilize them more frequently.

The same could be true of the summer squashes—both the yellow crookneck and pale green zucchini—and the cucumbers—one a pickling variant and the other a slicing type—all of which we planted in more or less the same area (the ground surrounding the planters) and with roughly the same soil (equal parts of compost and peat moss).

Despite these similarities, however, their performance was quite different.  Three of the four summer squash vines were hugely productive (especially the alpha crookneck; see August 6, 2013) whereas the cucumbers produced only a modest quantity of fruit before fading away in mid-summer.  Two other factors could account for the differences.

First, the amount of soil we introduced for the cucumbers was much, much less than for the squashes.  This is partly because of their location between the pool fence and planters but mostly because the cucumbers were the last seedlings we planted.  By that time, we were tired!  Our native soil is rocky and very difficult to dig but we will have to face up to doing more of it this year.  Adding to and amending the soil will be an early spring chore.

Second, the cucumbers were stricken hard by powdery mildew and once afflicted, perished rapidly.  It is not clear (and probably never will be) whether this was due to their undernourished state or simply because the varieties we planted are more susceptible than others to powdery mildew.  The squashes, on the other hand, seem better able to continue to produce after contracting the disease.  Each of the squash vines was still setting fruit into the fall.

Both of these are factors we can mitigate—or try to mitigate, anyway—and so we will plant both types of summer squash and both types of cucumbers again.  To help control the powdery mildew (which is endemic in the northeast), we will plant in new locations.  I will also arm myself with a spray bottle full of baking soda solution which I will apply early and often.  With diligence—and luck—we will have more squash and cucumbers than we can eat this year.

The string beans weren’t the only plants that got pulled out this weekend.

The tomatoes, about which I have been obsessing lately, have not been improving despite my pruning of several days ago (see September 27, 2013).  Once infected with late blight (the suspected culprit), the plants have little hope of recovery without the use of fungicides.  Late blight is caused by oomycetes, non-photosynthetic fungi (perhaps that’s redundant?) that spread through the production of millions of oospores.  Oomycete is a cool word but it is a very uncool organism.

I have read about using a baking soda spray in several publications and websites (see, for instance, Late Bloomer’s Episode 2.16) and will probably try that next year, starting early in the season to prevent onset.  We’ll plant the tomatoes in the west planter—the best we can do, in terms of crop rotation—and keep everything as clean as possible.  However, given the ease with which the oospores spread and their ability to survive, underground, through severe weather, we are at a disadvantage (and greatly outnumbered).

It’s much too late for any kind of spray this year so I pulled out the spindly vines of the Sungold, Black Cherry, Brandywine (red and yellow) and Aunt Ruby’s German Green tomatoes that remained.  There were plenty of green (i.e., unripe) tomatoes but none that were fit to eat.  On all of the plants suffering from blight, the disease had spread to the fruit.  I don’t mind a rotten spot or two or even the occasional wormhole or bird peck, but the brown lesions, with their white spore sites, make even the best looking tomato unappetizing.

I’m happy to say that the plants were otherwise healthy and had produced extensive root systems (which required a fair amount of effort to pull out).  I was also pleased (and surprised) to see that the Country Taste Beefsteak tomato vines continue to resist the late blight; there were no signs of the lesions or brown spots on the leaves or stems.  This makes them a very good candidate for next year’s garden.

Of course, they are suffering from something else, possibly Septoria leaf spot (my hypothesis is based on review of photos of afflicted plants online) or maybe early blight.  Unfortunately, all of these conditions are spread by spores, the production of which is favored by the cool, humid weather that occurs in the fall.  I left the beefsteaks alone (well, I may have trimmed a few branches) in the hope that we will be able to harvest the dozen or so ripening tomatoes that are still on the vine.

Warning:  Insect photo below.

Over the last few days, the blight (or whatever it is) that has been affecting the cherry tomatoes almost completely overwhelmed them.  There are now only a few branches that are not mottled or completely brown.  This is the first time we’ve had a disease that affects the fruit.  Clearly, it is time for some aggressive pruning.

In the process of amputating the diseased branches, I uncovered four hornworms (I would say that my worst fears were confirmed except that I have come to accept their inevitable presence).  None of them was very large and one was quite small; two had been visited by braconid wasps and were carrying egg sacs.  And despite their numbers, they had done relatively little damage.  Instead of killing them, I simply pruned the branches on which they were munching and tossed them onto the refuse pile.

When I had snipped away all of the afflicted Sungold and Black Cherry vines, there was not much left to look at, perhaps one gangly stem per plant, several feet long, with a small fan of leaves and a few clusters of tomatoes at the end.  I carefully draped the stems over the top of the supporting cages to prevent breakage or kinking.  Some of the remaining fruit has nearly ripened so the season is not quite over for them.

Inspecting the other tomato plants, I found that the Aunt Ruby’s German Green and the Red Brandywine vines are suffering from the same disease; many of their branches, leaves and fruit are similarly overcast with a sickly brown pall.  I took the same approach as with the cherry tomatoes and pruned away the damaged branches.  Not surprisingly, I also found more hornworms.

Much earlier in the season (see September 2, 2013), the Country Taste Beefsteak tomatoes became ill but with something different.  Instead of a uniform brown cast, their leaves are speckled with small, brown polka dots.  Eventually, the leaves turn yellow, wither and then die.  Sometimes, the fruits develop the same spots but these do not otherwise impair their color, ripening or flavor.  Just to be on the safe side, I pruned away most of the afflicted branches.

The only tomato plants that do not seem to be suffering are the Yellow Brandywines.  Given their close proximity to the others, however, I do not give them much of a chance to remain disease-free.  Still, the season will probably end due to weather before a possible infection can have an effect on production.

After I was finished, it looked like the tomato plants had been given a military haircut.  There are next to no branches on the vertical portion of the stems and the foliage is only slightly bushier at the top.  On the positive side, there are still plenty of tomatoes left.

Many of which are green, including a big bowl of cherry tomatoes and several of the other varieties that were attached to the branches I had to prune (a handful ended up in the garbage because they were almost completely covered with the blight).  We’ll make the most of them:  one green tomato casserole coming up.