Resource Guide for Organic Insect and Disease ... - Cornell University

to control corn earworm (Barber 1944). The “Zea-later” is a tool marketed for applying a mix of
plant oil and Bt directly into the silk channel of corn to control the corn earworm (Hazzard &
Westgate 2004). As a fungicide, oils are primarily effective against powdery mildews.
Sams and Deyton (2002) state that oils are “the only widely used class of pesticides to which
insects or mites have not developed resistance.”
FORMULATION AND APPLICATION GUIDELINES:
Pure oils need emulsifiers to stay in suspension when they are mixed with water. Most oil
products have an emulsifier already added. Detergents or surfactants may also be added to oil
sprays or incorporated into oil products; while these ingredients may show some pest control
efficacy themselves, they are usually considered to be inert adjuvants (Stansly et al. 2002).
Good coverage is important. Several applications may be needed for full control of some pests.
Phytotoxicity can be a problem; it can show up as visible leaf damage or, more subtly, as yield
reduction. In one study, while bi-weekly oil applications reduced whitefly counts on tomato
leaves by two thirds, yield on the oil-treated plants was also reduced compared to untreated
plants (Stansly et al. 2002). In another case, five oil sprays controlled powdery mildew in grapes,
but sugar levels were reduced (Northover 2002).
Follow label recommendations to minimize phytotoxicity. Oils that evaporate very slowly have
higher chances of phytotoxicity. For this reason, oil applications are not recommended on very
humid days. Some crop varieties may be extra-sensitive. Oils are incompatible with sulfur and
copper on some crops.
In order to avoid phytotoxicity on apples, VanBuskirk et al. (2002) recommend:
• Use oil in a dilute application (with a minimum of 200 gallons/acre on apples).
• Do not exceed an oil concentration of 1% (volume to volume).
• Do not apply when temperatures exceed 80 degrees F.
• Avoid large droplets.
• Ensure good tank agitation.
• Make sure oil is completely emulsified.
An oil product that makes a pesticide claim must be a registered pesticide, or in the case of
certain essential oils, it may qualify as a pesticide that is exempt from registration. Other oil
products are sold as stand-alone adjuvants, for use in tank mixes with registered pesticide
products. Adjuvants do not have to be registered with the EPA, though a few states require
registration. Be sure to follow label instructions in all cases.
OMRI LISTED PRODUCTS (This is a partial list. Check http://www.omri.org for many more):
Petroleum oils:
Organic JMS Stylet Oil (JMS Flower Farms, Inc.)
PureSpray Green (Petro Canada)
SuffOil-X (BioWorks, Inc.)
Plant oils:
GC-3, (JH Biotech, Inc.)
Eco E-rase (IJO Products, LLC)
Golden Pest Spray Oil (Stoller Enterprises)
Green Cypress Organic Spreader (Monterey Chemical, Co.)
Natur’l Oil (adjuvant) (Stoller Enterprises)
Pest Out (JH Biotech, Inc.)
Vegol (W Neudorff GmbH KG)
Organic Resource Guide 145