Pesticides and Pollinators

adjacent habitat next to potato field
Bumble bee foraging on pollinator habitat adjacent
topotato crops. photo:  Krischik lab

Minimize the use of broad-spectrum pesticides. These are toxic to bees and other pollinators, and include neonicotinoids, pyrethroids, organophosphates, and others.

Consider alternatives to pesticides first. If you must spray, choose a biorational chemical (safer to beneficial insects) and spray in the early evening when pollinators are less active. Planting insect- and disease-resistant varieties, proper irrigation, nutrition management, and allowing beneficial insects and spiders to visit plants help reduce the need for pesticides.
The disappearance of pollinators and effects of neonicotinoid insecticides on pollinators highlights the question as to whether our risk assessment approach is adequate.

pesticides pollinators infographic
                infographic: Ohio State University

 

Pesticides and pollinators

 

Pesticide toxicity explained

potato plant sprayed
Potato crop sprayed with systemic insecticide.
photo:  L. Schneider

Pesticides include herbicides, fungicides and insecticides. Pesticide active and inert ingredients can be found on the label of the pesticide container. The active ingredient is the chemical registered by the EPA as toxic to pest and beneficial insects. Inert ingredients are penetrating agents, odor maskers, stabilizers, preservatives, diluents, surfactants, emulsifiers, propellants, solvents, spreaders, stickers, antifoaming agents, dyes, and drift retardants that modify the physicochemical properties of the spray mixture. Insecticides are designed to destroy both target and non-target insects. Recent papers demonstrate that some inert ingredients are also highly toxic to bees, and also fungicides demonstrated toxicity to bees. Numerous papers have shown that lower, sublethal amounts of insecticides affect behavior and alter the ability of insects to find food and survive. For these and numerous other reasons, insecticides are not safe to use around pollinators and other beneficial insects.  Read Understanding pesticide toxicity to pollinators . . .

What are systemic insecticides?


A systemic insecticide is absorbed into the plant's vascular system, leaving the entire plant toxic to both target and non-target insect species. Neonicotinoids are a class of systemic insecticide particularly harmful to bees and other pollinators. They have lethal and sublethal effects on insect species by affecting the central nervous system which results in paralysis and death. However, in spite of high toxicity to pollinators, neonicotinoids 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. 

Neonicotinoid application methods include seed treatments, foliar sprays, soil and trunk drenches, and trunk-injections. Flowering plants that open after systemic insecticides are sprayed can contain the insecticide residue for many months or more in the leaves, pollen and nectar. Avoid using systemic insecticides on flowering plants that pollinators visit. If a pesticide must be used, apply spot treatments of contact insecticides instead.

monarch larvae
Monarch (Danaus plexippus) larvae experiment on
neonicotinoid toxicity. photo:  Krischik lab

There are six neonicotinoid active ingredients:  imidacloprid, dinotefuran, thiamethoxam, and clothianidin, of which acetamiprid and thiacloprid are the least toxic to bees. Another systemic insecticide, fipronil, is used around buildings and is also toxic to bees. You can find these active ingredients listed on the insecticide label in small print.

The neonicotinoid class of insecticides is highly toxic to pollinators and kills bees at around 180 ppb in flower nectar or pollen. Sublethal doses of neonicotinoid insecticide starting around 10 ppb cause bees to lose navigation and foraging abilities. 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. Adult bees consume neonics which are stored in pollen and honey where they become concentrated, and are then fed to developing young.

What is Integrated Pest Management (IPM)?

Integrated Pest Management (IPM) is an approach to solving pest problems that applies knowledge about pests and plants to prevent plant damage early before it becomes a problem. IPM promotes multiple tactics to manage pests and suppress population size below thresholds that cause unacceptable levels of damage to plants or crops. Read  Guide to Integrated Pest Management (IPM) .  . .

Why insects versus pesticides

lady beetle beneficial
Predatory lady beetle (Coccinellidae) feeding on
Milkweed aphid (Aphis nerii).
photo: Pavlos Skenteridis, Bio-insecta
  • Conservation of natural enemies of insects (predators and parasitoids) to help suppress pest insects.
  • Conservation of pollinators (such as bees and beetles) to help increase crop yields.
  • Some pest insects can develop pesticide resistance with increased use of pesticides.
  • Pesticides kill both good and bad (non-target and target) insects including predator bugs, as well as important soil dwelling insect predators.
  • Beneficial insects are cost-effective and safe for humans, birds, wildlife and the environment.

More about beneficial insects and biocontrols . . .

Turf damage: insect or fungus?

turf with fungus damage
Turf with fungus damage.
photo:  Krischik lab

If your turf is plagued with brown patches, do not assume it is a grub like Japanese beetle. Most brown spots in turf are due to fungus, which are hard for even lawn care professionals to identify and manage, as different diseases require different fungicides. You may need to take a sample to the University of MN plant disease clinic to learn the pest species and how to manage it (https://pdc.umn.edu/  612-625-1275.)  For Japanese beetle grubs in the soil use GrubEx, and for adults feeding on plants, use Acelepryn; both contain biorational chlorantraniliprole. For all grubs use Bt galleriae or grubgone.  Native insect predators cannot kill enough grubs and adult Japanese beetles to manage their populations. Remember: Never spray any pesticide on flowers or when bees are foraging.

Mosquito control pesticides and pollinators

content to come . . .