Question
I use a foliar fertilizer about every two weeks on my whole garden during the growing season. I also use Neem extract as a pesticide, mildicide, etc. (also sprayed on). I need to know how soon I can use either one before or after use of the other; do they conflict with each other, or does the use of the fertilizer undo the pesticide activity of the Neem or otherwise preclude the other from being absorbed into the leaf? How do I use both on the same plants? And what about the use of BT or any other organic pesticide concurrently with foliar feeding?

Answer
Dear Jean:

I apologize for the delay in responding to your question.  First of all, I have limited experience using foliar fertlizers and Neem Oil extract.  I was intrigued with your question and began some research which provided little, if any possible conclusive data regarding the topic.

Based on my limited experience, I will offer an untested theory that the use of Neem prior to foliar feeding would limit the effectiveness of the fertilizer since the oily base created by the Neem would tend to limit the absorption. Therefore, I would conclude that a reasonable period of time, 3 to 6 days between application of fertilizer and pesticide would be appropriate.  Although. as a result of your question;  I have decided to experiment mixing and applying them concurrently and evaluate the results.  It's times such as these that makes me wish I was a better chemist and had listened more carefully during the chemistry classes!!

Sincerely,

Mack Jean
AllExperts
Master Gardener
Tennessee