Cucumbers Ain’t Doing Well

[Shean Smith]

Sorry for the incorrect English, but incorrect cukes are deserving of incorrect English. My bush cukes are developing ugliness on it’s leaves. I’m including some pictures of my cucumber challenge. With my hat in my hand I’m requesting someone with greater knowledge than me to shed some light on this blight (it had to rhyme). I have baking soda and API  “Leaf Zone” to mix up. I’ve already tried MaxiCrop; it’s been a day since I applied it. I also reapplied it this morning (4/26/12). Help anyone?

[Shean Smith]

Thank you for the assistance. I’ll tweak the Ph just a tad to bring the Ph between about 6.8. 

Larry said:

I have read that the iron should be a Tsp about once a month or so,  not a few times a week. also your PH is just a  touch low target 6.8 one up or down ok but tartget 6.8. With your Ph below 6.8 you can still get a chemical lock out of some nutriants.

Shean

“Live and learn; die and forget it all."

[Amanda Plante]

I agree with what's already been said about the potassium deficiency.  Keep an eye on it and see if the new foliage develops any issues or if the old foliage gets any worse.

The symptoms could also be attributed to a plant disease such as anthracnose.  Normally this would be treatable by applying fungicide.  In a hydroponic system, it can spread extremely easily from plant to plant.  I'm not sure what to do if you do have anthracnose in an aquaponic situation.  If I had anthracnose, I would remove the plants, let the water cycle for a few weeks, replace as much of the water as possible, maybe try your hand at a different crop from another plant family in the meantime.  But I could be wrong.  Best to wait and see how the plants respond to your treatment for K deficiency.

Stressed plants are also more susceptible to insect pressures.  I agree with the other posts that mention spider mites.  You can check for spider mites by placing a blank, white piece of paper under the leaf.  Shake the leaf over the paper.  If you have mites, you should see them crawling around on the paper.  You can treat with horticultural oil or insecticidal soap.  Once the plants start to recover from the K deficiency, they'll be less stressed and hopefully less susceptible to pest pressure.

[TCLynx]

Cucumbers like the lower pH though.  So my guess would be potassium deficiency, if you are using potassium bicarbonate, it will take care of bringing pH up as well as providing potassium.  Of course you have been using seaweed extract so that also provides plenty of potassium so I'm not really sure.  I always had really bad problems with cucumbers in AP because of my really hard water and high pH/overabundance of calcium with potassium and Iron lock out.

[Shean Smith]

Everything else is growing like their’s no tomorrow.

Everything’s dark green and lush with blooms and fruit,

and if it was possible, everything’s smiling at me as

if they were saying "thank you” (except the cukes

which are ingrates). I may try Will Allen’s idea and

put them in cocopeat and my worms’ castings in

pots within the bed. I’m making a smaller one, a one "IBC 

system," with the bed on top and will use it as a trial

by fire system to experiment with. Anyway as the

old saying goes, “Live and learn and then die and forget it all."

TCLynx said:

Cucumbers like the lower pH though.  So my guess would be potassium deficiency, if you are using potassium bicarbonate, it will take care of bringing pH up as well as providing potassium.  Of course you have been using seaweed extract so that also provides plenty of potassium so I'm not really sure.  I always had really bad problems with cucumbers in AP because of my really hard water and high pH/overabundance of calcium with potassium and Iron lock out.

[Shean Smith]

Howdy!

Auburn Extension answered my quarry with the following so you can pass this along. Of course the fungicide suggested isn’t fish safe so other means of prevention should be adhered to. All of my cukes were together so that’s why all of mine were sick.

Shean Smith

"From the photos, It looks like Alternaria Leaf Blight. This disease is caused by the fungus Alternaria cucumerina and causes small, tan spots to appear on the leaves, which can later enlarge to 1½ inches or more in diameter. Leaf drop can be severe. Bright sunshine, frequent dews or rain, and temperatures between 60 and 90 °F favor disease development. Prevention & Treatment: Remove and destroy all infected plant residues at the end of the gardening season, since the fungus survives the winter on plant residue. This disease is easily spread by tools, wind, splashing water, or insects. Rotation of crops and seed treatment will also help. When this disease occurs consistently in the garden, a preventative fungicide program can be followed. A couple of preventative fungicides for cucumbers are chlorothalonil and Maneb. These fungicides should be available at your local farm supply store. When using these fungicides, please read and follow all label directions for use."

TCLynx said:

Cucumbers like the lower pH though.  So my guess would be potassium deficiency, if you are using potassium bicarbonate, it will take care of bringing pH up as well as providing potassium.  Of course you have been using seaweed extract so that also provides plenty of potassium so I'm not really sure.  I always had really bad problems with cucumbers in AP because of my really hard water and high pH/overabundance of calcium with potassium and Iron lock out.

[Gary Lanning]

My cucumbers and beans look exactly like your pictures, Shean. I just checked the underside of the leaves with a microscope and they are infested with mites. 

[Shean Smith]

Are any of your other plants affected? 

Gary Lanning said:

My cucumbers and beans look exactly like your pictures, Shean. I just checked the underside of the leaves with a microscope and they are infested with mites. 

[Gary Lanning]

The beans and cukes are the worst but we checked all our plants today and found mites as well as thrips on the tomatoes, carrots, lettuce, swiss chard, and morning glories. The numbers are very low on these so I am going to try some organic controls like Neem oil and Mighty Wash.  

Shean Smith said:

Are any of your other plants affected? 

Gary Lanning said:

My cucumbers and beans look exactly like your pictures, Shean. I just checked the underside of the leaves with a microscope and they are infested with mites. 

[Shean Smith]

It appears like I have a "mitey big problem" in my one of my growbeds. It doesn’t appear as if my second growbed is affected at all (which my 'maters, peppers, and other nightshade veggies are in). Thanks again my friend for your illumination on this matter; you’ve been a great help to me by identifying this mitey big problem. I live in the Deep South near the Alabama Gulf Coast and there is a preponderance of critters, varmints, and pests that love gardens more than I do, evidently. It looks like my garden will require me to divide my husbandry skills between my bride of 19 years and my garden. :-) Have a great day!

Shean

Gary Lanning said:

The beans and cukes are the worst but we checked all our plants today and found mites as well as thrips on the tomatoes, carrots, lettuce, swiss chard, and morning glories. The numbers are very low on these so I am going to try some organic controls like Neem oil and Mighty Wash.  

Shean Smith said:

Are any of your other plants affected? 

Gary Lanning said:

My cucumbers and beans look exactly like your pictures, Shean. I just checked the underside of the leaves with a microscope and they are infested with mites. 

[Phil Slaton]

You've got to load those fish tanks with more fingerling fish.  50 fish are better than 49 for producing the nutrients that you need.  If you are using a clairfier, by pass it until your fish double in size.  Then open up a second system and move half the fish, also move a third to a half the water out of the first tank to the new tank.