Recommendations on a mandarin tree

[850FL]

I used cheap soybean oil to smother a highly scale-infested peach while it was still dormant and that was very effective. It was runny though, so I tied a grocery bag around the trunk to catch the excess (so it wouldn’t hit the roots). I should have added sulfur to the oil as a double wham to get any fungus. I was thinking also to use castor oil next time since it’s a lot more viscous and wouldn’t run, but castor may actually be too viscous and hinder budding nodes so maybe I should water it down with soybean or coconut oil or something. This could be an effective protocol for dormant trees.. perhaps even PT rootstocks.. in the rare event they’d even get pests.. as for normal evergreen citrus I would probably not attempt it this way.. except this does bring up the question, why are we spraying with expensive horticultural oils when cheaper alternatives might do the trick?

[brian]

I can't speak on the soybean oil vs hort oil subject, but I can say if you use pure oil or otherwise high concentrate oil it could kill your tree.  I accidentally did this when I was messing with a hose-end sprayer and let the mix get too strong.  I had a nice healthy guava tree that turned black and completely defoliated within a couple days of spraying it, and died shortly after.

For soap you can use Dr Bronners "pure castille soap".  I think it is cheaper than soap marketed as insecticidal.  You just want detergent-free soap, which is uncommon in grocery stores.

[containerman]

I can't speak on the soybean oil vs hort oil subject, but I can say if you use pure oil or otherwise high concentrate oil it could kill your tree.  I accidentally did this when I was messing with a hose-end sprayer and let the mix get too strong.  I had a nice healthy guava tree that turned black and completely defoliated within a couple days of spraying it, and died shortly after.

For soap you can use Dr Bronners "pure castille soap".  I think it is cheaper than soap marketed as insecticidal.  You just want detergent-free soap, which is uncommon in grocery stores.

Agreed

[Millet]

I certainly would not put horticultural oil in the category of expensive. Spraying a dormant leafless tree is one thing, but spraying a tree in full leaf is quite another.  I have used a horticultural oil (Brand name Ultra Pure) for control of mites, scale, aphids, thrips mealy bug, and white fly .  It works wonderful.  I apply in at the rate of 40 grams /gallon water.  There is a huge difference in leaf surface evaporation time between oils, and this is important for the life of the leaf, as Brian wrote above..  Whatever, horticultural oil one uses be sure it is a lite high quality oil.

[850FL]

Lol.. I was more speculating than anything about the use of edible oils and such (and would NEVER spray an evergreen with such) and honestly I think I did suffocate a twig or two on the peach. BUT I have wasted quite a bit of money spraying all the trees down during summer, between the use of neem, sulfur sprays, piperonal butoxide + pyrethrins, etc.. it’s kind of annoying.. rather would have a diy type of concoction that works well and is cheap..

[brian]

I see no reason why canola or soybean oil would not work in place of hort oil... but the unknown is always a bit risky so you have to consider if it is worth a chance of damaging your trees.  If you try it, let us know how it works out

[EricSC]

brian brought a good point.

I did see many articles or YouTube recommend vegetable oil, but some mentioned the vege oils may stay on leaves (due to high boiling point) so can catch dust or cause damage.