Archives for posts with tag: plant disorders

This year, I am determined not to lose the battle against powdery mildew.

It’s probably a futile goal—quixotic, really—because we have suffered it every year that we’ve kept the vegetable garden, starting in 2011. Spores of Erysiphe cichoracearum, the fungus responsible for powdery mildew in cucurbits, are present, brought here from elsewhere by the wind (most likely) or by spontaneous manifestation (not likely but it is easy to understand why people once believed in it).

Sadly, the fungus is well-suited to survival and produces resting spores called chasmothecia (all of this is according to the folks at UC Davis; see “UC IPM Online”) that can—and do—resist the freezing weather that kills off weaker organism over winter. The only way to eradicate it is with fungicide, the most effective of which I have no interest in using.

No, eradication is not the answer; management is. And the key to management of powdery mildew is anticipation and early detection. It will appear—that’s inevitable—so I must be ready for it. And that means starting to spray the leaves of the cucurbits, which in our garden are the cucumbers and squash, with a preventative solution and starting to spray them now.

Last year, I found a good recipe on Late Bloomer’s website (see “Late Bloomer – National Heirloom Expo 2013 – Episode 36”; there is other interesting stuff there) and I mixed up a batch today. It’s a simple concoction of water, baking soda, hydrogen peroxide, and dish detergent (which I suspect is there to help the solution adhere to the plant).

I made a loop through the garden this afternoon, spraying each cucumber and squash leaf as I passed. My intuition tells me that spraying while the garden is in direct sunlight is preferable because the sun will evaporate the water, leaving the NaHCO3 and H2O2 (I have no idea what is the chemical formula for dish detergent but it’s probably too long to fit) behind to coat the leaves and inhibit fungal growth.

For the remainder of the season, especially in the fall when the humidity of summer remains but the nights are cooler, I will have to re-spray on a weekly (or so) basis.

Maybe I can’t win the battle but perhaps if I am diligent, I (and the cucurbits) won’t be routed.


After yesterday’s efforts (see June 14, 2015), today’s planting was a walk in the park. Make that a walk in the garden.

We have three varieties of cucumber to plant today: Alibi Pickling Cornichons and Tanja Slicing, same as last year, and Early Fortune, new to our garden. Last year’s varieties have a slight edge (we started them earlier) but all of the seedlings look strong.

To help them along, we sprinkled a tablespoon of bone meal into each hole before setting a seedling on top. The Calcium that should slowly leach into the soil will help the cucumber plants form flowers and will minimize blossom end rot. At least, that’s what they say on the internet.

And they wouldn’t say it if it wasn’t true. Right?

More snow yesterday—a lot more snow—means that it is still too early to be thinking about starting any work on the garden outside.  At this rate of snowstorms, we won’t be digging out until March.

That is just as well because there are still a few items from last year to recap.  Most notably, there are the results of the soil testing that arrived at the end of October (2013) but which I have not had a chance to discuss.

Based on the previous year’s testing, I was not expecting any startling new information for the east and west planters (see October 19, 2013, part 2).  Sure enough, the reports confirmed my expectations.  The all-important pH of the soil remains within the sweet spot (6.20 to 6.80) for vegetable gardens with the east planter at 6.57 and the west planter a tad more acidic at 6.23.

Interestingly, the soil pH of the east planter increased slightly (from 6.31 in 2012) while the soil pH of the west planter decreased (it was 6.78 in 2012).  The soil in the east planter is now squarely within the preferred range but the soil in the west planter is bouncing from endpoint to endpoint.  Both are perfectly fine, however, and we will not have to make pH adjustment to either.

Similarly, the macro- (Ca, K, Mg and P) and micronutrient (B, Cu, Fe, Mn and Zn) concentrations in the east and west planters are close to each other, a result, I think, of at least three factors.  First, we treat the planters identically; neither has received any amendments (other than a top dressing of compost at the beginning of the season) or more fertilizer than the other.

Second, we have been rotating crops back and forth between the planters.  Therefore, their soils have been depleted (or replenished) by more or less the same amount.  Third, the age of the soil in each planter is more than two years.  I assume that given their consistent treatment, both soils are converging on the same steady state.

For the most part, the micronutrient levels in the west planter decreased when compared to last year (i.e., 2012).  This is not too surprising, again considering that we don’t heavily fertilize or otherwise modify our soil during the growing season (I think of it as time smoothing the soil’s rough edges).  Micronutrient levels in the east planter are mostly the same as 2012 (its soil is older and smoother).

What I didn’t expect is that in both planters, the concentration of Calcium increased by almost 50 percent.  We did not add lime, bone meal or any other source of the micronutrient so I have no idea from where the additional Calcium comes.

So much for the well-established planters.  On to the ground level soil, where we planted squash and cucumbers last season.

For starters, the pH of this soil is too high at 7.10 (the soil is slightly alkaline).  We’ve learned from both of the growing seasons prior to last that this can have a very detrimental effect on plant performance.  And I learned from this year’s experiments with seed starting mix that the culprit is probably not the very acidic peat moss, of which the ground level soil is roughly half.  The other half is compost (mainly cow manure) which tends to be more alkaline.

When we dig new pits for the squash and cucumbers this year, we will have to increase the proportion of peat moss to manure and perhaps add some elemental Sulfur to bring the pH down.  Otherwise, the ground soil profile resembles that of the planters.  The macro- and micronutrient concentrations are very close, including—somewhat mysteriously—the high concentration of Calcium.

This is a bit ironic because the summer squash plants experienced a high rate of blossom end rot last season, a condition that is usually associated with Calcium deficiency.  I think this is what the testing lab was alluding to when they called me in the fall (see October 24, 2013).  The testing methods based on acid extraction indicate a high concentration of Calcium but it is not, apparently, in a form that plants can readily use.  I’ll have to look into this one further.

The reports list lots of numbers, not all of them obviously meaningful.  So, what does it all mean?  The bottom line is that our planters’ soil is doing fine and that with minor modification the soil in the ground will come into line as well.  That’s good—if not exciting—news.

It is the first day of fall (by some, but not all, reckonings; see June 25, 2013) and the weather shows it.  It was rainy and blustery last night, cool and damp this morning.  The frogs, apparently in denial, still swim around the pool but with grimaces on their faces.  The water is cold.  It has been too cold for me lately, too.

There are many, many cherry tomatoes on the Sungold and Black Cherry vines, most of them green.  And most of them have been falling off with each raw gust of wind.  The Sungolds in particular do not enjoy this cooler weather.  Even the tomatoes that turn the characteristic brilliant shade of yellow are about half the diameter of their peak-season counterparts.

In fact, I’m a bit worried about the Sungold vines.  They seem to be infected with some type of disease.  First the leaves, then the stems, and finally the tomatoes themselves turn a sickly shade of brown.  It is an eerie effect, not unlike the moon eclipsing the sun and casting the daytime world into a gloomy twilight.  Unfortunately, it is not a condition that is likely to pass as quickly (or at all).

Just when you think you’ve had everything dealt to you and just when you think you’ve dealt with it all; just when you think there couldn’t possibly be another plant disease or chomping insect or marauding animal that you haven’t seen; just when you think that maybe, just maybe, you’ve got a few things figured out and maybe, just maybe, you have everything under control; well, that’s when Mother Nature serves you up something new and unexpected.

I’m exaggerating a bit, of course, and we have had a successful and relatively uneventful year in the garden.  But after morning inspection and a nice swim, I looked over to the east planter and saw a pile of what looked like sawdust at one corner, clear evidence of carpenter ants.  These guys aren’t after our vegetables or even the leaves or soil.  No, it is the planter itself that they are eating.  Well, strictly speaking they don’t eat the wood but they do tunnel through it.  If left unchecked, the ants’ nesting will weaken the boards, accelerate their natural decay and eventually lead to their crumbling (structural engineers these ants are not).

When carpenter ants appear around the house, I sprinkle a few teaspoons of poison in their path which, if I am lucky, they take back to the nest and share with their siblings.  With further luck (and so far, so good), the colony dies.  This is one of the few occasions where I will resort to nasty chemicals—potentially, the integrity of the house depends on it.  I have never needed much nor needed it very often and our accumulated exposure has been relatively low.

Unfortunately, I can’t use any poison in the planter.  Granted, the carpenter ant infestation appears to be well below the vegetables (at the bottom of the planter) but it is very possible that the plants’ roots have extended that deeply.  Even if not, I do not want any dangerous chemicals that close to our food.  After all, I chose to use untreated lumber to build the planters; using a chemical pesticide would not be consistent with that philosophy.

So, what to do?  It’s not like I can ask them to leave.

On the other hand, maybe I can give them a reason to leave.

I brought the hose over to the nest’s entrance and set the sprayer to “jet”.  Then I placed the nozzle directly against the side of the planter—point blank range—and turned the water on full.  Any tunnels, caverns or shafts that the ants had created should have been instantly flooded, and possibly collapsed.  At least, I certainly hope so.

Problem solved?  We shall see.

We are still experiencing blossom end rot of the crookneck squash.  It is not affecting every fruit, however, and despite losing two or three potential squash, we were able to harvest two healthy ones.

At the same time, we also picked two of the Cavili zucchini.  These turn out to be a pale green variety (as opposed to the more typical dark green type) and are best picked small (about four inches in length).

Blossom end rot is caused by a deficiency of Calcium in the soil.  The soil in which our squash plants are growing should be rich in minerals but it is new, by which I mean it has not been tested; we do not know its balance of macro- and micronutrients.  It could easily be short on Calcium or perhaps overly acidic.

We have a friend who swears by bone meal.  Whenever she plants a squash or tomato plant, she sprinkles a handful of it into the bottom of the hole.  That way, she knows that the plant will have a ready source of Calcium.  We have rarely done this (based on the results of soil analysis and, admittedly, laziness).

We’ll keep an eye on the squash plants and if the end rot persists, will consider adding Calcium in some form (bone meal is slow so a liquid form may be more efficacious).