Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
effects on species and/or degrade environmental quality. The lack of data on the toxicity of
degradates for many pesticides would represent a source of uncertainty for assessing risk.
An USEPA-approved label specifies whether a product can be mixed with one or more pesticides.
Without product-specific toxicological data, it would not be possible to quantify the potential effects
of these mixtures. In addition, a quantitative analysis could only be conducted if reliable scientific
information allowed a determination of whether the joint action of a mixture would be additive,
synergistic, or antagonistic. Such information would not likely exist unless the mode of action would
be common among the chemicals and receptors. Moreover, the composition of and exposure to
mixtures would be highly site- and/or time-specific and, therefore, it would be nearly impossible to
assess potential effects to species and environmental quality.
To minimize or eliminate potential negative effects associated with applying two or more pesticides
as a mixture, the use would be conducted in accordance with the labeling requirements. Labels for
two or more pesticides applied as a mixture should be completely reviewed, where products with the
least potential for negative effects would be selected for use on the refuge. This is especially relevant
when a mixture would be applied in a manner that may already have the potential for an effect(s)
associated with an individual pesticide (e.g., runoff to ponds in sandy watersheds). Use of a tank mix
under these conditions would increase the level of uncertainty in terms of risk to species or potential
to degrade environmental quality.
Adjuvants generally function to enhance or prolong the activity of pesticide. For terrestrial
herbicides, adjuvants aid in the absorption into plant tissue. Adjuvant is a broad term that generally
applies to surfactants, selected oils, anti-foaming agents, buffering compounds, drift control agents,
compatibility agents, stickers, and spreaders. Adjuvants are not under the same registration
requirements as pesticides and the USEPA does not register or approve the labeling of spray
adjuvants. Individual pesticide labels identify types of adjuvants approved for use with it. In
general, adjuvants compose a relatively small portion of the volume of pesticides applied. Selection
of adjuvants with limited toxicity and low volumes would be recommended to reduce the potential
for the adjuvant to influence the toxicity of the pesticide.
7.4 Determining Effects to Soil and Water Quality
The approval process for pesticide uses would consider potential to degrade water quality on and off
refuge lands. A pesticide can only affect water quality through movement away from the treatment
site. After application, pesticide mobilization can be characterized by one or more of the following
(Kerle et al. 1996):
• Attach (sorb) to soil, vegetation, or other surfaces and remain at or near the treated area;
• Attach to soil and move off-site through erosion from run-off or wind;
• Dissolve in water that can be subjected to run-off or leaching.
As an initial screening tool, selected chemical characteristics and rating criteria for a pesticide can be
evaluated to assess potential to enter ground and/or surface waters. These would include the
following: persistence, sorption coefficient (Koc), groundwater ubiquity score (GUS), and solubility.
Persistence, which is expressed as half-life (t½), represents the length of time required for 50% of the
deposited pesticide to degrade (completely or partially). Persistence in the soil can be categorized as
Appendix G. Integrated Pest Management G-31