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Clarence, NY

Does over watering cause the older leaves on the plant to turn yellow? The leaves further out on the main and secondaries look fine.

6/29/2007 5:20:29 PM

Ctpumpkin@optonline.net

Several factors can cause this & over watering is one....It can cause Nitrogen leaching &/or anaerobic Nitrogen losses. Ate the new leaves slow growing, light green & small?

Mites can also cause older leaves to die. Do you know how to check for them?

6/30/2007 12:04:13 AM

Clarence, NY

The leaves are large and the plant looks normal otherwise. If it's mites - I don't know how to check. Mites sound like a really bad thing.

6/30/2007 8:10:23 AM

Clarence, NY

I just thought of something else that may be causing this problem. I put a thin layer of SEVEN-5% dust on the leaves to stop the cucumber and Jap beatles. Is this a bad thing?

6/30/2007 10:05:55 AM

Ctpumpkin@optonline.net

Sevin could cause leaf injury (phytotoxicity) if it was applied during warm weather.

Sevin also kills the beneficial insects that eat mites so this reinforces the mite theory. The more a grower uses Sevin, the more likely they'll see mites become a problem.

Take a sheet of clean white paper. Hold it UNDER a suspect leaf. Tap the top of the leaf several times. Look at the paper for small dots (smaller than the head of a pin). Watch carefully...do any of the dots move? Rub one with your finger. Does it smear? If so that's a mites "gut smear".

A 10X hand lens is good but a 25-35X macroscope is a great tool for identifying mites.

You might also see webs & eggs on the leaf bottoms if you have good lighting & a lens.

6/30/2007 11:53:29 PM

Clarence, NY

Tremor - Thanks I'll check it out and stop using the SEVIN

7/1/2007 8:25:22 AM