Insecticides used in greenhouse and landscapes and toxicity to pollinators
Do systemic, neonicotinyl insecticides contribute to pollinator and beneficial insect decline?
The conservation of beneficial insects, that includes bees, insect predators, parasitic wasps, and butterflies, is an essential part of Integrated Pest management (IPM) programs. IPM promotes multiple tactics to manage pests and to suppress the population size below levels that will damage the plant. IPM tactics include cultural control, sanitation, biological control, using insecticides friendly to beneficial insects, and finally the use of conventional insecticides. IPM recognizes that the few remaining pest insects will support beneficial predators and parasitic wasps. When scouting plants for pest insects, check for populations of both pest and beneficial insects, such as lady beetles and bees. If beneficial insects are present, wait to spray insecticides to see if the beneficial insects control the pest insects or use specific insecticides that only target the pest insect. Do not apply insecticides while plants are in full bloom. If possible avoid beneficial insects by spraying leaves in the evening when bees and lady beetles are not foraging.
Neonicotinoid systemic insecticides have been implicated in the decline of bees, butterflies, and other beneficial insects. The European Union banned the use of neonicotinoid insecticides from 2014-2016 on crops and plants that bee's visit. The concern was the residue in pollen and nectar and their negative affects on survival and foraging behavior of bees.
There are few systemic insecticides, while there are many systemic herbicides and fungicides. Systemic, neonicotinoid insecticides are the most widely used insecticides in the world, due to their low mammalian toxicity and the ability of the insecticide to move systemically from soil into the entire plant, including pollen and nectar. Application methods include seed treatments, foliar sprays, soil and trunk drenches, and trunk-injections. Flowers that open after being sprayed with contact insecticides do not contain insecticide residue, while toxicity to pests lasts for 1-3 weeks. However, flowers that open after systemic insecticides are sprayed can contain the insecticide residue for many months in both the leaves and pollen and nectar.
There are six neonicotinoid active ingredients, imidacloprid, dinotefuran, thiamethoxam, and clothianidin, of which acetamiprid and thiacloprid are the least toxic to bees. There is another systemic insecticide, fipronil, that is used around structures that is also toxic to bees. You will find these active ingredients listed on the insecticide label in small print. The neonicotinyl class of insecticides is highly toxic to bees and kills bees at around 180 ppb in flower nectar or pollen. However, sublethal doses of neonicotinyl insecticide starting around 10 ppb, causes bees to lose navigation and foraging skills. The longevity and amount of the neonicotinoid in the pollen and nectar will depend on application method, concentration applied, and binding capacity of the soil.
The use of neonicotinyl insecticides as trunk injections and soil drenches for ash trees is important to slow the spread of the exotic, invasive Emerald Ash Borer and other invasive pests. As bees do not collect ash pollen in quantities, the risk to bee pollinators is low. In contrast, the use of neonicotinyl insecticides on flowering garden plants, shrubs and trees, including linden and basswood trees can kill bees and beneficial insects that utilize the flowers for pollen and nectar. It is wise to avoid using systemic neonicotinyl insecticides on flowering plants that bees visit regularly. Instead use spot treatments of contact insecticides.
The new EPA bee icon and bee advisory box on insecticide labels
EPA has added new language to neonicotinyl insecticide products (imidacloprid, dinotefuran, thiamethoxam, and clothianidin) to protect bees and other insect pollinators. The bee icon above signals that the pesticide has potential to harm bees. The language in the new bee advisory box explains application restrictions to protect bees.
Bee and other insect pollinators can be exposed to the product from:
- Direct contact during foliar application or contact with residues on plant surfaces after foliar application.
- Ingestion of residues in nectar and pollen when the pesticide is applied as a seed treatment, soil, tree injection, as well as foliar application.
When using this product, take steps to:
- Minimize exposure when bees are foraging on pollinator attractive plants around the application site.
- Minimize drift of this product onto beehives or to off-site pollinator attractive habitat. Drift of this product onto beehives can result in bee kills.
Nursery and greenhouse growers have alternatives to systemic insecticides. For the last 10 years, the EPA has been registering selective, contact insecticides that conserve beneficial insects and pollinators.
- Pymetrozine (Endeavor), Flonicamid (Aria) stops aphids from feeing
- Pyriproxyfen (Distance), insect growth regulator, prevents larvae from developing into adults
- Beauveria bassiana (Botanigard) microbial
- S-kinoprene (Enstar II), juvenile hormone mimic
- Spinosad (Conserve, Entrust) bee friendly when dried
- Miticides (Akari, Hexygon)
Bee kills should be reported to Minnesota Department of Agriculture (www.mda.state.mn.us, type bee kill into search), National Pesticide Information Center (http://npic.orst.edu/), and the EPA (firstname.lastname@example.org).
Insecticide Toxicity to Bees By Active Ingredient for Nursery and Landscape
Insecticide Toxicity to Bees in Consumer Products Used in Landscape
This table lists the trade names of insecticides available to homeowners. The common names of the insecticides are followed by the commercial trade names. Not all products are listed in this table. Be sure to read the label.
References to commercial products or trade names are made with the understanding that no discrimination is intended and no product endorsement by the University of Minnesota Extension is implied. From: Krupke, C.H., et al. 2012. Beekeeping: Protecting Honey Bees From Insecticides. Purdue Extension E-53-W. URL: http://extension.entm.purdue.edu/publications/E-53.pdf ; Nixon, P.L. 2011. Names of General Use Insecticides. University of Illinois. URL: http://ipm.illinois.edu/hyg/insects/insecticide_trade_names_for_homeowners.pdf