While oil treatments have historically targeted fruit trees
and woody ornamentals, several different types of pesticide oils are currently
marketed for house plants, flowers and vegetables. Commercial oil products
include emulsifiers to enable the oil to mix readily with water. These
emulsifiers are generally considered to be inert, but may have some
insecticidal properties. Oil formulations are generally designed to be mixed
with water at concentrations of 0.5-2.0 percent (volume/ volume). When applying
oils, it is best to agitate hand pump sprayers frequently and keep tank spray
agitators running. This reduces the risk of oil separation that could result in
sprayer clogging, uneven plant coverage and possible plant injury.
Oils will separate from the carrier. Agitation is necessary
to keep oils in solution.
When mixed with other pesticides, oils can enhance
application efficiency. Oils often act as surfactants, and improve plant
coverage and penetration of pesticides into leaf surfaces. Always read
pesticide product labels carefully to make sure the product can be mixed with
oil. Most labels prohibit the use of sulfur pesticides within 30 days of oil
treatment. Oils may be incompatible with copper applications in some crops.