4 years ago



New research shows that

New research shows that neonicotinoids are common in streams and rivers of the Midwest (Hladik et al. 2014), where they have been found in a number of samples at levels associated with toxicity to insects, and thus may be a threat to monarchs in this central breeding region. In one of the first major investigations of water contamination from multiple neonicotinoids in the United States, Hladik et al. (2014) sampled surface waters in corn and soybean regions centered in Iowa and found that neonicotinoids are mobile and that they persist in the environment. The amounts and kinds of neonicotinoids applied, timing of their use, and precipitation events determined the pattern of neonicotinoids in streams (p. 191). Neonicotinoids were detected at all of the sites sampled, including large and small watersheds draining regions with different percentages of corn and soybeans (p. 192). Small watersheds with large percentages of row crops had the highest levels of neonicotinoids in surface waters. Summarizing the results (p. 189), “[m]aximum and median concentrations (maxiumum:median) across all sites and samples followed the same pattern as detection frequencies with clothianidin (257 ng/L; 8.2 ng/L) > thiamethoxam (185 ng/L; < 2 ng/ L) > imidacloprid (42.7 ng/L; < 2 ng/L) (Table 2). Multiple neonicotinoids were common, with three neonicotinoids detected in 23% of the samples.” Many samples had levels that are in the range known to be toxic to insects (e.g. Goulson 2013, p. 905: 5 - 10 ppb neonicotinoids in crop tissues control insect pests), and at levels that are associated with declining bird populations in Holland (Hallman et al. 2014: greater than 20 ppb imidicloprid in surface water is correlated with 3.5% annual decline in birds). Another threat from neonicotinoids to monarchs comes from some nursery-grown milkweeds and nectar plants purchased from garden centers. As public awareness of the plight of monarchs grows, increasingly monarchs are being encouraged to lay eggs and sip nectar in butterflyattracting gardens, both as a conservation measure and as a source of entertainment. Neonicotinoids have been detected in approximately half of nursery-grown plants tested (Brown et al. 2014), and there are anecdotal accounts of monarch larvae not surviving on nursery-grown milkweed plants, consistent with toxicity from systemic insecticides. In California alone, where the state’s Department of Pesticide Regulation collects detailed pesticide use data, 2,447 pounds of imidacloprid were applied to nursery plants in 2012 (California Department of Pesticide Regulation 2014, p. 414-415). These products are also widely used around homes, and products approved for home and garden use may be applied to ornamental and landscape plants, as well as turf, at significantly higher rates (up to 32 times higher) than those approved for agricultural crops (Hopwood et al. 2012). Taken together, the cumulative impacts of these exposures to neonicotinoids throughout the monarch’s habitat, particularly in their main breeding range, pose a significant ongoing and increasing threat. Mosquito Control Programs Insecticides are used in many areas of North America to attempt to manage mosquito larvae and adults, often in response to mosquito-borne diseases such as West Nile virus and dengue fever, or to control nuisance populations. Some models suggest that higher global temperatures will extend the geographic ranges of some mosquitos that vector diseases (Reiter 2001), which will likely lead to an increased use of insecticides targeting mosquitos. Mosquito control is done using agents that kill the adult (adulticides) or immature (larvicides) forms of the insect. The Monarch ESA Petition 98

most commonly used adulticides are organophosphate (e.g., malathion, naled) and pyrethroid (e.g., pyrethrin, permethrin, resmethrin, sumithrin, prallethrin) insecticides (Mazzacano and Black 2013). These compounds have broad -spectrum toxicity and can cause severe impacts to non-target animals including butterflies. General losses of biodiversity in insect communities that affect a wide range of orders and families have been noted by some researchers in areas where mosquito adulticides are sprayed (Eliazar and Emmel 1991, Kwan et al. 2009). Multiple studies have also shown negative impacts of mosquito treatments specifically on butterfly populations. Barrier treatments, in which pesticide applied as a spray to foliage forms a coating that kills adults that come into contact with it, can have lethal and sub-lethal effects on adult or immature butterflies. The decline of the federally endangered Schaus swallowtail butterfly (Heraclides aristodemus ponceanus), endemic to southern Florida, has been linked to pesticide applications for mosquito control (Eliazar and Emmel 1991), as has the decline of the Miami blue butterfly (Cyclargus thomasi bethunebakeri) (USFWS 2012, 77 FR 20948). Mosquito-control pesticides are also considered to be a contributing factor in the extinctions of the Florida zestos skipper (Epargyreus zestos) and rockland grass skipper (Hesperia meskei pinocayo) (see: ). In areas that are being treated for mosquitoes, monarchs can be exposed to the insecticides at the larval stage if the insecticides are over-sprayed or drift onto milkweed hosts, or as adults if butterflies are flying or visiting nectar plants during or after applications. Researchers at the University of Minnesota investigated toxicity to monarchs of two insecticides often used to control mosquitos (Oberhauser et al. 2006, Monarch Joint Venture 2014), and found that monarchs did have higher mortality when exposed: The University of Minnesota conducted research on how monarch larvae and adults were affected by exposure to insecticides commonly used in mosquito control (resmethrin and permethrin). These pyrethroids can be sprayed as ultra-low volume treatments or as barrier treatments. Ultra-low volume treatments intended to affect insects as they are flying, whereas the barrier treatments remain on leaves, providing a barrier to mosquitoes that may not be out foraging during the day. Both the ultra-low resmethrin study and the barrier permethrin study showed negative impacts on monarch larvae and adults. Leaves from the barrier treatments resulted in higher mortality to monarch larvae than control leaves up to 3 weeks after the initial application (Monarch Joint Venture 2014). Increased mortality of monarchs from mosquito control programs is thus a significant potential threat, although impacts have not been assessed. Grasshopper Control on Rangelands in the Western United States Insecticides are commonly used in rangeland areas across many western states to control native grasshoppers that compete with cattle for forage. When grasshopper numbers are high, the Animal Plant Health Inspection Service (APHIS) routinely facilitates spraying of insecticides to control Mormon crickets and grasshoppers on public and private lands. APHIS lists three Monarch ESA Petition 99

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