I have a couple of insect issues that are a bear (for me). Leaf miners and squash vine borers. Both of these are in some manner inside the plant and conventional foliar spraying is not working for me or does not work. Bacteria that will harm these insects wont enter the plant tissue. One needs something systemic (that is not outright harmful to the environment and humans).

I read Neem oil does not get absorbed significantly from foliar sprays. But when applied as a drenched it is picked up by the roots and becomes systemic. And the insects that eat the plant die from it.

(That it can be absorbed through the roots but not the leaves does not sound right. Almost everything that the roots can absorb the underside of leaves can absorb. Certainly there can be more to this.)

I have not seen extensive evidence in literature that indeed Neem oil does become systemic and that it will thus protect from pests applied in this way.

But I have read anecdotal articles and seen YT videos where people claim it has worked for them against certain insects. Also that it guards against fungus such as mildew.

I absolutely want to try Neem drench on a few of my plants. Namely, swiss chard and summer squashes.

My initial concerns are:

1) How old does a plant have to be before you can apply?

2) If the Neem oil is systemic, wont I taste it in the chard leaves and squash fruits? Neem oil is devastatingly bitter.

Please share if you have any experience using Neem oil as a soil drench or please comment what you think about this?

Thank you so much!