Horticultural or neem oil and Passiflora

[estación seca]

Update. The scale came back. I sprayed with neem oil and it didn't kill them. I'm going to take cuttings. When I have them rooted I'll throw away the big plant and treat the small ones repeatedly with alcohol.

[Roberta]

Originally Posted by Fuerte Rav

Hi
Still 'Neem' but off of the original tack of this thread - hope that's OK?

I gave all my Phals their monthly shower of Neem and Hort soap today, no problem there BUT I forgot that I had a tray of rooted Milkweed cuttings that I had just potted up nearby. Now Neem and Monarch caterpillars don't mix well and I'm sure these young plants will have caught some spray/drift. Has anyone any idea how long the Neem will stay active in the Milkweed plants? I've put netting over these milkweeds for the time being to stop the butterflies laying eggs on them but I'm going to have to construct a cage with fine mesh that caterpillars can't get in through from other parts of the garden as well.



It's actually been quite a good learning point. I was going to put the milkweeds in a border amongst some hibiscus but I have to spray the hibiscus with Neem or a chemical pesticide 3 or 4 times a year against cochineal so I need to think again about where I plant them!

Any advice about longevity of Neem gratefully received!

I don't think that Neem has that much of a residual effect - it kills what it hits, just like the horticultural oil. The smell may have some slightly lasting effect but I don't think that it will harm the Monarchs. A wash with soapy water would certainly remove it. You probably do want to plant your milkweed where it's not going to get hit when you spray other things. And certainly if a pesticide is involved you don't want to get that on the milkweed.

[yug]

I had a Passiflora edulis var flavacarpa growing near my orchids and dragon fruit a number of years ago. Any place where the passion fruit vine came in contact with either one of those died back. There must have been something in the passion fruit plant that kills back any competing plants. Sort of like chemical warfare in the plant kingdom.

[Ray]

The active ingredient in neem oil is azadirachtin, and it is absorbed by the plant from the oil, so even if you wash off the oil, the effects may linger.

However, I found this somewhere:

Azadirachtin, a major component of neem oil, is rapidly broken down. Microbes and light break down the pesticide in soil, water and on plants. The half-life of azadirachtin in soil ranges from 3 - 44 days. In water, the half-life ranges from 48 minutes to 4 days. It also rapidly breaks down on plant leaves; the half-life if 1 - 2.5 days. The remaining components of neem oil are broken down by microbes in most soil and water environments.

That doesn’t actually tell us the durability if the anti-insect properties of azadirachtin absorbed by the plants, but it does provide some inkling of info.