Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 218

turf, and ornamental plants. Chlorpyrifos can be applied on foliage, tree bark or soil
as a pre- or post-emergent spray in water to control insects or mites. It may also be
applied to soil as a spray or as granules to control soil-dwelling insect pests. Maximum
single application rates range from 1.12 to 4.5 kg CPY ha −1 for granular products and
0.53-6.27 kg CPY ha −1 for spray application. Multiple applications of the granular or
flowable formulations are allowed on many crops. There are many crops that receive
treatment around planting time, post-harvest or during dormancy. For crops such as
apple, applications of CPY are delayed until after bloom, and as noted previously, no
application is permitted when bees are actively foraging (Solomon et al. 2014 ).
Chlorpyrifos is widely used on corn, soybeans and wheat in the corn belt that
extends from Quebec through the Midwestern U.S. to Manitoba. In the Great Plains
regions of North America the main uses are on alfalfa and sunflower. In California,
Florida, and Georgia, CPY is used on vegetables, citrus, and tree nuts (Gomez 2009 ).
Other crops treated with CPY include cotton, cranberries, sorghum, strawberries,
peanuts and wheat. Some of these crops are highly or partially dependent upon
pollinators, or are utilized as forage or nesting material for pollinators (e.g., alfalfa
leaf cutting bees). The importance of pollinators in production of tree fruit is well
recognized (NAS 2007 ). For example, it is estimated that over 60% of honey bee
colonies in the U.S. are used each year for pollination of almonds (Carman 2011 ).
Cotton and soybeans are not critically dependent on pollinators, but bees will forage
readily on the flowers of these crops (Berger et al. 1988 ; Rhodes 2002 ) and on extra-
floral nectaries of cotton (Willmer 2011 ).

2.2 Scope of the Assessment

The potential for exposure of pollinators to CPY is recognized. Since the primary
insect pollinators are bees (superfamily Apoidea), labels for CPY products include
warnings not to apply the product or allow it to drift to flowering crops or weeds if
bees are visiting the treated area, and advise users to inform local beekeepers prior
to application if hives are in or adjacent to fields to be treated. Labels describing
restrictions on use and best application practices also include instructions to mini-
mize spray drift to reduce harmful effects on bees in habitats close to the application
site (Solomon et al. 2014 ). For this reason, adverse effects due to negligence or
actions contrary to precautions specified on the label were not included in this
assessment. It is assumed that applications are made by trained applicators and that
all instructions on the label are followed. This assessment focused on incidental
exposure during applications to crops listed on the current labels under conditions
specified by the labels. A search for documented incidents of harm to commercial
beehives from CPY was also conducted through the USEPA and the Health Canada
Pest Management Regulatory Agency (PMRA).
Because bees are considered the dominant animal pollinators and are prominent
in agricultural landscapes (NAS 2007 ), toxicity data used in the risk assessment
focused mainly on bees. There are more than 17,000 species of bees worldwide