Pesticide toxicity to bees

Pesticides vary in their effects on bees. Contact pesticides are usually sprayed on plants and can kill bees when they crawl over sprayed surfaces of plants or other areas around it. Systemic pesticides, on the other hand, are usually incorporated into the soil or onto seeds and move up into the stem, leaves, nectar, and pollen of plants.^[1][2]

Of contact pesticides, dust and wettable powder pesticides tend to be more hazardous to bees than solutions or emulsifiable concentrates. When a bee comes in contact with pesticides while foraging, the bee may die immediately without returning to the hive. In this case, the queen bee, brood, and nurse bees are not contaminated and the colony survives. Alternatively, the bee may come into contact with an insecticide and transport it back to the colony in contaminated pollen or nectar or on its body, potentially causing widespread colony death.^[3]

Actual damage to bee populations is a function of toxicity and exposure of the compound, in combination with the mode of application. A systemic pesticide, which is incorporated into the soil or coated on seeds, may kill soil-dwelling insects, such as grubs or mole crickets as well as other insects, including bees, that are exposed to the leaves, fruits, pollen, and nectar of the treated plants.^[4]

Pesticides, especially neonicotinoids, have been investigated in relation to risks for bees such as Colony Collapse Disorder. A 2018 review by the European Food Safety Authority (EFSA) concluded that most uses of neonicotinoid pesticides such as clothianidin represent a risk to wild bees and honeybees.^[5][6] Neonicotinoids have been banned for all outdoor use in the entire European Union since 2018, but has a conditional approval in the U.S. and other parts of the world, where it is widely used.^[7][8]