Category Archives: Diseases

Powdery Mildew Strikes Again

We have had a very cooler and wet spring and the powdery mildew is back with a vengeance.

A day before our last good rain, I sprayed all of my crops with a mixture of Garrett Juice (2 tbsp per gallon), neem oil (almost 2 tbsp per gallon), and a tablespoon per gallon of ocean minerals.  After wards, the leaves had a nice rich green shine to them and the powdery mildew could not be seen.  I suspect that it was just hidden under the glossy finish.  After a few more days of very light sprinkles, enough to wash the spray off, I can again see spots of powdery mildew all over.

I had a small pump bottle of copper fungicide, so I sprayed the most affected leaves.  Tomorrow when I go to town I will look for a concentrated bottle of copper and I plan to add that to my spray mixture of Garrett Juice, neem and ocean minerals.

Neem oil can treat fungus, mites and insects, with varying efficacy.

It starts with just a few small spots here and there.

powdery mildew on squash plants

Then it spreads.

powdery mildew on squash closeup

Another squash leaf.  Different varieties of summer squash and zucchini have differing tolerances and immunity to the powdery mildew.   Winter squash and gourds seem to have the strongest resistance, except for spagetti squash.

powdery mildew on squash plants

I cut out the leaves that are totally wiped out by the mildew.  They are light yellow, covered with the white mess and dry and stiff.  The powdery mildew if a parasite fungus that taps into the leaves and feeds off of the squash leaves.

 

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Squash Issues – Yellowing Leaves on Some Plants

In one of my raised beds, I have some squash plants – both summer yellow and zucchini – that are turning yellow.   In the neighboring bed some of the late planted squash appears to be stunted.  This is affecting the older leaves first.  The edges turn yellow and the leaf surface is splotched with yellow areas.  (This year I am growing some of my summer squash – both yellow and zucchini – in tomato cages to see if I can get a better control over the plants that would otherwise sprawl all over.)

The little squash plant to the front left of this caged plant appears to be stunted.  The plant to the back, right of the center caged plant is OK.  The problem plants are intermixed with plants that are just fine and looking good.  This is a pointer to mosaic virus as opposed to a nutrient deficiency.  I have a hard time thinking that a nutrient deficiency would only affect intermittent plants when the soil was turned over and mixed before planting.
summer squash leaves are yellowing

And a closeup:  The younger leaves are OK so far.
summer squash leaves are yellowing

After spending hours searching for an answer, the 2 most promising answers are either a nutrient deficiency or a mosaic virus.

Below is a broader view.  Some of the plants are affected while others aren’t.  To add more confusion, I only made note of the varieties that I originally planted, not the subsequent 3 re-seedings that I had to do because of poor germination.  (I don’t know why the seeds did not germinate well, the original planting was 2 year old professional seed that has been stored in the refrigerator.)  The 2 original varieties were Superpik yellow and Obsidian zucchini, both on the Cucumber Mosaic Virus Resistant list at Cornell’s Squash resistance lists.

What is affecting my squash does not look exactly like any mosaic virus images I found, neither does it look exactly like Zinc deficiency, although it does look a wee bit more like the zinc deficient images.  It could also be magnesium or manganese deficiency.

So what to do?  I am not ready to pull the plants because I don’t know for sure if it is a mosaic virus.  I am going to water the squash with a handful of Epsom salt in the water.  Maybe I can crush a few zinc vitamin pills and add it to the magnesium sulfate mix.
summer squash leaves are yellowing

Oh what to do?  I have squished a few squash bugs and scraped numerous batches of eggs off of the leaves.  My research has revealed that aphids and cucumber beetles are the culprits that transmit mosaic viruses, not squash bugs, although squash bugs are blamed for transmission of some plant diseases.  No clear answer.

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What Is The Problem With These Broccoli Leaves?

Some of my broccoli seedlings are developing spots on the leaves.  They are mostly a black spot and gray on the bottom of the leaf.  This problem is affecting the bottom most leaves first and sort of working its way up the plant.  This problem is affecting only some of the beds with broccoli planted in and not other beds.

I can’t treat the problem until I can correctly diagnosis it.

broccoli leaf spots

This is the bottom of a broccoli leaf.  The leaf in the top right corner is a basil leaf.  The spots look different – probably another problem.

leaf spots on bottom of broccoli leaves

Looking online, I found 2 possibilities:  Downy Mildew – and alternaria.  Actually, it doesn’t resemble absolutely either issue, aka black leaf spot and gray leaf spot.

Downy Mildew  –  Peronospora parasitica

  • Gray-white sunken leaf spots which are often angular and restricted by the leaf veins
  • Leaf tissue around the spots turns yellow
  • Fuzzy gray growth can be seen on the underside of the leaves
  • Numerous black sunken spots can form on infected heads
  • Disease is common in cool wet weather

Black Leaf Spot/Gray Leaf Spot  –  Alternaria spp.

  • Gray to black round leaf spots with concentric rings
  • Leaf tissue becomes dry, brittle and often falls out, resulting in a ‘shot hole’ appearance
  • Leaf spots often appear first on lower older leaves

Neither of these symptoms absolutely accurately describes the problem, so I don’t know what to think. At this point, I can only hope that the issue stops racing up my broccoli plants. We had several days of wet weather, but are going to be dry for a few weeks – hopefully this will help.

Update- I did a bit of online research and decided to spray the plants in question.  I added 4 tsp of baking soda and 1 ounce of Need oil to a gallon of water (but only used half of it – put the other half gallon in a jug -hopefully it will keep for a week or so in case I need to spray again).   I sprayed the broccoli and cabbage plants with yellowing leaves.  I sprayed mostly the bottom of the leaves, but of course lots of the spray also got on the top of leaves.  I am a bit concerned about spraying baking soda on plants – previous experience has showed me that squash plants do not like this solution on their leaves.  Will update and let you know how this spray worked on the broccoli leaf spots.

Update Update- as of early December, these plants are under a plastic hoop cover.  There is very little trace of yellowing or spotted leaves, but the plants seem stunted.  Other broccoli & cabbages planted outside in the old tomato bed have grown taller than these, as have a few brocs in an adjacent covered bed.  It could be that two treatments killed off what I think was downy mildew, or could be the cold weather – we had to very cold blasts early in November – but for whatever reason, the surviving plants don’t seem to be growing as they should – in fact, they don’t look like they have gotten any bigger in the past month!  Also, this is the same half of the garden where my yellow wax beans that I planted in late summer did not thrive – DowAgriscience’s environmental toxin Aminopyralid revisited??

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Yellowing Squash Leaves – Chlorosis?

I have about 2 summer squash plants in one bed that have leaves that are yellowing and decaying.  This is one summer squash, planted among other squash.  Only this one plant has this issue.  The older leaves turned yellow between the veins, then dried to whitish.  The edges curl up and the leaf finally dries up.  The new inner leaves are fine for a while.  I decided to cut these bad leaves off, leaving the hollow stems, just in case it is a virus.  You can see the plant to the right, it is just fine.
yellowing squash leaves

This other plant, thru the raised cattle panel, about 2 feet further along the bed, also has some of these leaves.  I decided to cut them off also.
yellowing squash leaves

I have done a search as to what could be causing this problem.  The most likely culprit seems to maybe be chlorosis.  Chlorosis is a nutrient deficiency although I don’t know what nutrient it could be.  I found this: “Iron, sulfur and manganese deficiencies cause yellowing in the younger leaves first, while nitrogen, magnesium and molybdenum deficiencies first afflict the older leaves”.  I have what I need to rectify nitrogen and Mg deficiency:  blood meal and epsom salt.  It won’t hurt to spread a little bit of both around.  However, I still don’t understand how just 2 of a dozen plants have this problem.  I also have some organic fertilizer with lots of trace elements in it.  I think I will spread a bit of these 3 substances around these plants tomorrow.

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Anthracnose on Peppers

Some of my peppers appear to be afflicted with anthracnose, a fungal problem caused by Colletotrichum piperatum growth.  These are two peppers that never made it to maturity.  They were supposed to be Chocolate Bell peppers.  My Pimento peppers have also suffered from this problem.  I do not plan to save any Chocolate bell pepper seeds this year.  I have picked 2 Pimento peppers that were anthracnose free but I do not plan to save their seeds – I don’t plan to grow pimentos again for a long time.
anthracnose on peppers

I throw these diseased peppers out in the trash, or burn them.  I do NOT compost them – I don’t want to spread the fungus all thru my garden by way of compost.

Other peppers have been affected to a lesser extent.  Only the fruit seems to have problems, not the plants themselves.  Early in the growing season I did have a problem with my pepper plants – they were too light green and I seem to have corrected that issue with fertilization.  This would mean that my plants were stressed all thru the growing season, along with being planted later than optimal.

Doing a bit of research, I have found that chili anthracnose disease/Colletotrichun is a big problem world wide and that pepper production is severely infected by anthracnose which may cause yield losses of up to 50%.  It can survive in and on seeds – so I only save seeds from mature, healthy peppers.

I have researched the subject, but can only guess that the spores blow around and land on the plants and then do their damage.  I have to think that my pimento seeds may have harbored the problem because last year they were severely afflicted with anthracnose.

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A Sample Pepper Harvest

The peppers were planted late, also, but they are producing fairly.  I learned that I can plant my peppers twice as dense in a raised bed next spring.  I had never planted them is a 5′ x 16′ raised bed before, so I wanted to leave them plenty of room to expand.  Lesson learned:  they don’t need the room that I left them.  I had planted 3 to 4 plants across the 5′ length, only about 10 rows along the 16′ length.  Next spring I plan to start twice as much pepper seeds – that means 144 plants instead of 72 seedlings.
a days pepper pickings

The large red peppers in the center top are Cubanelle peppers, a very nice sweet pepper.  The orange peppers in the top right are Tequila Sunrise, a mildly hot pepper.  The long red peppers under the Tequilas are Jimmy heirlooms, a nice sweet, thin skinned pepper.  Under them are Cayenne hot peppers.  To the left of the small cayenne are a red and a green heirloom jalapeno pepper.  The seeds are only viable from the red, mature jalapeno.  Under and next to them are more cayenne peppers, including 1 green one.  In the bottom left corner is another Tequila Sunrise.  The yellow/green peppers on the lower left side are Sweet Banana peppers – heirlooms.  Above them on the left are red Chili peppers.  I originally got these seeds from a dried chili pepper at Kroger.  Finally, the orange pepper on the upper left corner is a Golden Marconi, a sweet pepper.  My Golden Marconi peppers did not grow as large as normally this year.  I am hoping that the seeds are still genetically good and that the smaller size was due to new, not very fertile soil.  I will plant these seeds next year and if the peppers do not grow to their usual larger size, I may have to purchase new heirloom seeds.

Next year I will not be growing 2 varieties of peppers that I had previously grown for years:  Brown Bell and Pimento peppers.  This year, they were stunted and the peppers that grew to somewhat maturity were afflicted with what appears to be anthracnose.  I tossed these peppers and plants in the burn pile – they will NOT be composted so as to not spread what ever it is that is afflicting the peppers.

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Verigated Squash Leaves vs. Powdery Mildew

I received a comment questioning whether powdery mildew might actually be the natural coloring of certain squash leaves. I am creating this post in reply.

This first picture if of a normal variegated squash leaf. Some squash plants, especially winter squash plants, have leaves with white areas. These white areas are usually at the junction of leaf vines.

verigated leaf
This next picture is of small powdery mildew spots – note the fuzzy look to the round splotches randomly located all over the leaf:

powdery mildew

This leaf has powdery mildew spots all over it’s surface.  Note that the variegation is always at the angle corners of leaf vains.
verigated squash leaf with powdery mildew

Hope this can help you differentiate between normal leaf variegation and powdery mildew.

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A Week of Rain Destroys a Squash Garden

This part of Texas is usually hot and dry during the summer.   This past week we had a very unusual event:  7 days of rain.    Every day we had some rain.   Some days we had over 2 inches and other days we had an eighth or a quarter inch of rain.  The total rain for the week was a bit over 6 inches.   You might think this is a good thing.  Not so – we had rain every day.   Along with high humidity, we had very little sunshine to dry the leaves off.   I went out to the garden a few times during the week and sprayed Neem oil on the leaves, but the rain every day just washed it off.

Before the week of rain, I had been battling powdery mildew, but the rain spread the stuff all over the garden.  I can clearly see where the white stuff dripped to leaves below, to infect them.  I can also see where it splashed around, spreading it thru rain drops.

This 8 Ball zucchini is totally infected with powdery mildew.    This is rather unusual – these hybrid zucchini plants had showed themselves to be somewhat resistant to powdery mildew.
powdery mildew zucchini

Here are some more zucchini plants that have a heavy, thick coating of powdery mildew.  See how terribly thick those white spots are.
powdery mildew after rain

This squash plant is fatally infected with powdery mildew.
powdery mildew

This yellow summer squash plant is just about dead from powdery mildew.   All of the older leaves are fatally infected.  There just isn’t enough plant left to support the growing tip – this plant will probably die before it produces another squash.    It was a full, happy plant until the week of rain spread the mildew and killed the plant.
squash almost killed by powdery mildew

Another picture of powdery mildew all over zucchini leaves.  The stuff is ALL OVER!
powdery mildew on zucchini

Look at these leaves –  the powdery mildew is on every plant in the garden.   It must have been spread by the rain that splattered all over the garden for a week.
powdery mildew closeup

These cucumber leaves seem fairly resistant to the powdery mildew blight, but the older leaves have some strange tan spots and holes in them.   I don’t know what caused those holes.
cukes with holes in leaves

The older leaves on these zucchini plants are totally destroyed and it has spread to the new growth.  I sprayed the entire garden with Neem oil today, but most plants are t00 far gone to survive much longer.   The powdery mildew is just too rampant.

All squash plants are affected, even the once resistant hybrid zucchini and Waltham butternuts.  I have found out that Crenshaw squash are super- sensitive to powdery mildew.
grey zucchini with powdery mildew

This pic was taken before the rain week.  It shows what powdery mildew does to leaves.  A mild case of powdery mildew causes the leaves to become dry and stiff.   They then dry out, develop holes and then die.  This is the result of a mild case of mildew – after the week of rain I have a massive infection of powdery mildew.  I can see it killing entire groups of leaves at a time.
old leaves killed by powdery mildew

I usually burn my old squash plants at seasons end – I do not put them in the compost if they show any sign of disease of bug infection.  I’m not sure if powdery mildew will preclude my composting these plants.  I really do need green plants in the compost, but I don’t want to risk feeding the compost pile an organism that may survive composting and spread next season.  I’ll have to do some research on this matter.

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Overview – From July 10

This is the middle walkway between the 2 long rows of raised beds.  The beds are 5 feet wide and 16 feet long – to accommodate the 16′ cattle panels.  I planned to plant climbing plants – mostly beans, squash and cucumbers – under the cattle panels on both sides of the bed and plant other things along the outer 2 feet of each long side.  I planted these squash so that they could grow down into the 4′ aisle between the beds.  In the very front, left you can see a long vine growing along the outside of the raised bed.  This is one of 4 Crenshaw winter squash that I grew.  These seem overly sensitive to powdery mildew and I don’t believe they will live long enough to produce a single fruit.   The winter squash growing on the cattle panel on the front left are several varieties including Seminole pumpkin.  These did very well last year.  On the bottom right side is the cattle panel where my cucumbers are growing.

At the top middle left of the pic is the raised cattle panel on which my Long Red Chinese Beans are growing.  They have really taken off  but have yet to start producing the 12″ red ‘green’ beans.  At the old place, I grew them up twine in a narrow bed in front of the carport.  That gave them at least 10′ – which still wasn’t enough room.  These cattle panels are no where high enough for the beans.  They are growing wildly, but when I try to tuck the growing ends in and out of the cattle panels, they easily snap.  Next year I will have to find some place better for them to grow.
overview july 10

I need to get the garden in on time next spring.

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Squash and Zucchini

Because of out move, the entire garden was put in a month late. This has resulted in several issues.  Some of the plants didn’t mature enough before the heat – and some plants are actually stunted.  I didn’t get enough production out of the plants before the heat and drought hit.  You can see the powdery mildew on these leaves.  This zucchini is a Grey Zucchini – an heirloom that is one of my favorite zucchinis.
grey zucchini closeup

This is an overview of a row of Patty Pan summer squash.  The plants are strong and large with plenty of  baby buds along the stems.  It is almost ready to produce.  This pic was taken 2 weeks ago and we have had a week of rain that has taken its toll on the vegetable garden by spreading powdery mildew.  These yellow squash are susceptible to the mildew.   I have yet to harvest a Patty Pan squash out of this garden.  The variegated squash leaves in front of the cattle panel are some hybrid butternut varieties planted to grow up the panels.

grey zucchini

This is a closeup of some of the yellow summer squash plants.  There are plenty of buds along the strong stems and a burst of baby leaves and buds at the growing tip.  Hope these plants live to produce what looks so promising on them.  You can see the powdery mildew splotches on surrounding leaves.

yellow crookneck squash

This is a Cocozella  heirloom zucchini, one of my 2 favorite heirloom zukes.  Notice the thick leaf mulch under the plants.

cocozella zucchini

Another closeup of a Cocozella heirloom zucchini.  The mature leaves show the ravishes of powdery mildew.

cocozella zucchini

A closeup of some hybrid zucchini plants.  You can see an Obsidian zuke on the plant in the front right side.  Overall, these were fairly strong plants that produced well – because the were planted before the rest of the zukes and squash.

obsidian zucchini

These are my first 2 Waltham Butternut winter squash.  The little one on on the left is no longer with us – it must have died and fallen off when I wasn’t looking.  Usually Walthams do better than this bunch has done – but they are also usually planted a month earlier than I planted these.  There are, though, many buds on these vines.  Overall, Walthams are somewhat resistant to powdery mildew, although I am seeing it on some Waltham Butternut leaves.  I planted seeds from several sources and am assuming that all Waltham Butternuts are open pollinated unless other wise stated, meaning that all of these Walthams should be very similar.

waltham butternut

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