June 2023 - 8

perspectives
BY JULIE GRAESCH
Oils, Myth & Magic
Julie Graesch is
biological program
manager for insects
at BioWorks. She is
a member of GPN's
40 Under 40 class
of 2022 and can be
reached at jgraesch@
bioworksinc.com.
Horticultural mineral oils (HMO) have been
on the market for over 100 years. Early oil
formulations were heavy and contained volatiles
that were often phytotoxic. Over time, the quality
of oil products has improved significantly,
with an increase in the range of plants
that can be treated, as well as the range
of arthropods and diseases that can be
controlled simultaneously. In addition
to arthropod suffocation and cuticle
disruption, certain oils can elicit behavioral
effects such as repellency, antifeedant
and anti-oviposition properties. This can
be especially true for products containing
essential oil(s). Oils have many beneficial
properties: safety for workers, limited side
effects on natural enemies (no harmful
residues), efficacy on par with chemical
pesticides, utility as carriers or adjuvants,
and no resistance concerns.
When considering HMOs, be aware of
information on the label. First, oil concentration
can vary from product to product. Typically,
products contain 80 to 98% mineral oil. UltraPure
Oil is an example of a 98% oil, and SuffOil-X
is an example of an
80% oil. Does a lower
oil concentration
mean lower efficacy?
In the case of
SuffOil-X, the oil in
the formulation has
been homogenized,
or broken down to
where the oil droplets
are extremely small,
creating an oil-water
emulsion. This creates
several advantages;
first, the oil behaves
more like a chemical
and will readily go into suspension. The small
droplets remain in suspension longer and do not
separate (agitation is still necessary). Second,
applying less oil to the plant reduces the risk of
8 JUNE 2023 GPNMAG.COM
phytotoxicity; however, due to the formulation
and oil droplet size, the same level of disease
and/or arthropod control is still achieved. Finally,
once applied, the oil will coat and penetrate
tiny arthropod spiracles but will not clog plant
stomata or inhibit the plants' ability to transpire.
Another important item on the label is the
unsulfonated residue (UR) percentage. This
number is typically listed immediately below the
oil concentration. The UR value is a measure
of the degree of refinement of an oil and an
indication of the phytotoxic materials that remain
after the distillation and refining process. An oil
with a high UR (≥ 92%) is free of most impurities
and is a good measure of overall quality. Oils
with UR of <92% are potentially more phytotoxic
on plants. Myth: UR does not correlate to the
amount of sulfur the product contains.
Have both HMOs
and 25(b)s on hand and
use them in rotation.
Choose which product(s)
to use based on the
pest and the current
circumstance.
MINIMUM RISK PESTICIDES
FIFRA 25(b) exempt oil-based products,
on the other hand, contain active and inert
ingredients that are considered minimum risk
and are registered under Section 25(b) of the
Federal Insecticide, Fungicide and Rodenticide
Act (FIFRA).
Products with
25(b) exemption
do not need
EPA registration
and are exempt
from regulations
on efficacy and
toxicity; however,
they still need to be
registered for use in
each state.
The mode of
action (MOA) of
25(b) products
is related to the
type(s) of formulated essential oil(s). MOA
may include suffocation, cuticle disruption,
repellency, antifeedant, anti-oviposition, etc.,
but some essential oils can also increase pest
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June 2023

Table of Contents for the Digital Edition of June 2023
