Milkweed plants bought at nurseries may expose monarch caterpillars to harmful pesticide residues

Halsch, Christopher A.; Hoyle, Sarah M.; Code, Aimee; Fordyce, James A.; Forister, Matthew L.

doi:10.1016/j.biocon.2022.109699

Cited by 8 publications

(3 citation statements)

References 29 publications

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“…As public interest and effort in biodiversity conservation continues to grow, nursery production of host plants will likely follow. Thus, the relevance of pests and their management on wildlife-friendly ornamentals to biodiversity conservation will also increase [ 66 ]. Although it is well supported that some insect herbivores outbreak on urban plants [ 7 ], this response can vary by insect life histories and local landscape characteristics [ 67 ].…”

Section: Discussionmentioning

confidence: 99%

Aphid infestations reduce monarch butterfly colonization, herbivory, and growth on ornamental milkweed

et al. 2023

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Anthropogenic disturbance is driving global biodiversity loss, including the monarch butterfly (Danaus plexippus), a dietary specialist of milkweed. In response, ornamental milkweed plantings are increasingly common in urbanized landscapes, and recent evidence indicates they have conservation value for monarch butterflies. Unfortunately, sap-feeding insect herbivores, including the oleander aphid (Aphis nerii), frequently reach high densities on plants in nursery settings and urbanized landscapes. Aphid-infested milkweed may inhibit monarch conservation efforts by reducing host plant quality and inducing plant defenses. To test this, we evaluated the effects of oleander aphid infestation on monarch oviposition, larval performance, and plant traits using tropical milkweed (Asclepias curassavica), the most common commercially available milkweed species in the southern U.S. We quantified monarch oviposition preference, larval herbivory, larval weight, and plant characteristics on aphid-free and aphid-infested milkweed. Monarch butterflies deposited three times more eggs on aphid-free versus aphid-infested milkweed. Similarly, larvae fed aphid-free milkweed consumed and weighed twice as much as larvae fed aphid-infested milkweed. Aphid-free milkweed had higher total dry leaf biomass and nitrogen content than aphid-infested milkweed. Our results indicate that oleander aphid infestations can have indirect negative impacts on urban monarch conservation efforts and highlight the need for effective Lepidoptera-friendly integrated pest management tactics for ornamental plants.

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Section: Discussionmentioning

confidence: 99%

Aphid infestations reduce monarch butterfly colonization, herbivory, and growth on ornamental milkweed

et al. 2023

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“…Plants in some retail nurseries have insecticides at high concentrations; for example, Halsch et al (2020) found mean concentrations of cyantraniliprole at >500 ng/mg, together with other types of insecticides such as bisamides, diacylhydrazines and neonicotinoids. In another retail plants study (Halsch, Hoyle, Code, Fordyce, & Forister, 2022), clothianidin was found at up to 2.58 ng/g and imidacloprid at up to 37.69 ng/g. Nectar from directly‐sprayed clover had up to 2992 ng/g and clothianidin and 6588 ng/g of imidacloprid, but concentrations were reduced by 99.4%–99.8% in blooms after mowing (Larson, Redmond, & Potter, 2015, reviewed in Zioga, Kelly, White, & Stout, 2020).…”

Section: Introductionmentioning

confidence: 93%

Adult monarch butterflies show high tolerance to neonicotinoid insecticides

Prouty

Bartlett

Krischik

et al. 2023

Ecological Entomology

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Numerous studies have documented the negative effects of neonicotinoids on bees; it remains crucial to examine how neonicotinoids affect other non‐target nectar‐feeding insects, such as the monarch butterfly, Danaus plexippus. Wildflowers growing near agricultural areas can be contaminated with neonicotinoids that affect survival or cause sublethal changes to behaviours of nectar‐feeding insects. Nectar residues of imidacloprid and clothianidin found in milkweeds and wildflowers adjacent to agricultural field range from 0 to 72.8 ng/mL. At field‐relevant doses, two neonicotinoids (imidacloprid and clothianidin) were studied for their effects on adult monarch survival, reproduction, flight and behaviour. First, we fed adult monarchs artificial nectar solutions ranging from 15 to 386 ng/mL of imidacloprid and 19 to 531 ng/mL of clothianidin. Neonicotinoid ingestion slightly reduced monarch reproduction but had no significant effects on survival, weight change, or activity levels. Second, we fed monarchs higher clothianidin doses (909 and 4030 ng/mL), that exceed field‐relevant levels by 22 and 99 times. These higher doses reduced monarch nectar consumption, survival, flight performance and reaction time in response to a drop test. Results show that adult monarchs tolerate field‐relevant doses as high as 54 ng/mL for imidacloprid and 75 ng/mL for clothianidin, with minimal lethal or sub‐lethal effects until much higher doses are supplied. We conclude that adult monarchs are more tolerant of ingested clothianidin and imidacloprid than indicated by previous research.

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“…Meanwhile, non-target effects of pesticide use and overuse also pose threats to many butterflies, often in landscapes already transformed by non-native plants [19,20]. While the use of neonicotinoids, in particular, has often been singled out, these are not the only harmful compounds present on landscapes at concentrations that are biologically relevant for butterflies [21,22]. Yet another threat being faced by butterflies is the accelerating influence of climate change.…”

Section: Introductionmentioning

confidence: 99%

Additive and interactive effects of anthropogenic stressors on an insect herbivore

2023

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The pressures of global change acting on wild plants and animals include exposure to environmental toxins, the introduction of non-native species, and climate change. Relatively few studies have been reported in which these three main classes of stressors have been examined simultaneously, allowing for the possibility of synergistic effects in an experimental context. In this study, we exposed caterpillars of the Melissa blue butterfly ( Lycaeides melissa ) to three concentrations of chlorantraniliprole, under three experimental climates, on a diet of a native or a non-native host plant throughout larval development in a fully factorial experiment. We find that high pesticide exposure and a non-native diet exhibit strong negative effects on caterpillars, resulting in 62% and 42% reduction in survival, respectively, while interactive effects tend to be weaker, ranging from 15% to 22% reduction in survival. Interactive effects have been shown to be strong in other contexts, but do not appear to be universal; however, our study shows that the cumulative effects of stressors acting in isolation (additively) are sufficiently strong to severely reduce survival and by extension population persistence in the wild.

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Milkweed plants bought at nurseries may expose monarch caterpillars to harmful pesticide residues

Cited by 8 publications

References 29 publications

Aphid infestations reduce monarch butterfly colonization, herbivory, and growth on ornamental milkweed

Aphid infestations reduce monarch butterfly colonization, herbivory, and growth on ornamental milkweed

Adult monarch butterflies show high tolerance to neonicotinoid insecticides

Additive and interactive effects of anthropogenic stressors on an insect herbivore

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