Penetrants and Surfactants used in Vista, southern CA

Before using an adjuvant with a pesticide, check whether one is needed or would negate the main product. For example,

  • Some insecticide products such as liquid BT and Spinosad are very good penetrants on their own and addition of a penetrant or surfactant can have poor results
  • Other insecticide products such as Ortho Tree & Shrub *Fruit Tree Spray and Voliam Flexi have a surfactant built in so there is no need to add another


  • LI 700. Very good for enhancing herbicides. Otherwise I’ve discontinued it on cultivated plants because leaves show signs of toxic effects afterwards.


  • Hi-Wett. Very effective. Typical dosage is 1 ml to 3 ml per gallon, the latter when rain is imminent.
  • Neem Oil concentrate. Typical dosage is 1 ml to 1 tsp per gallon, the latter for better protection against rain.

Note that Neem Oil is not an effective pesticide, as shown in Organic Agriculture trials by the Farm Extension in San Diego county 20 years ago. It does not contain any viable quantity of insect toxin. It will slow down weak insects but those that survive breed more vigorous populations. As was recently stated by the California Dept. of Agriculture:

“The biggest threat to U.S. Agriculture today are mis-informed home gardeners”

If you want to control insect and arachnid pests on your property with a spray or broadcast product, make sure the listed active ingredients include an insect or arachnid toxin.

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@Richard Are you saying that cold pressed neem oil has an inadequate concentration of the insecticide azadirachtin?
I searched but could not find any papers in peer reviewed journals that show that neem oil is not an effective pesticide.
Could you provide the reference for the findings of the Organic Agriculture trials by the Farm Extension in San Diego so that I may read what they had to say?

I use it as a paste slathered on just above the dirt line to deter borers. I think my experience is borne out by others including Michael Phillips. I certainly instinctively feel it keeps them at bay.

True, and also true in the neem oil concentrate. If an effective concentration were present it would be included in the active ingredients list on the label. Although it has been attempted, no certified lab has ever provided results to meet the U.S. requirements as an active ingredient in neem oil.

Note that Azadirachtin is not an insect toxin, but rather an insect growth regulator. If you want to control a pest with it, why not buy the Azadirachtin concentrate directly, e.g. Azatin® O (4.5%).