Pesticides can present danger to consumers, bystanders, or workers during manufacture, transport, or during and after use. There is concern that pesticides used to control pests on food crops are dangerous to the consumer. These concerns are one reason for the organic food movement. Food crops, including many fruits and vegetables such as apples, celery, cherries, grapes, nectarines, peaches, pears, peppers, potatoes, red raspberries, spinach and strawberries, may contain pesticide residues after being washed or peeled.

In the US, all materials intended for sale and use as pesticides must be registered with the EPA. The process may be long, complex and expensive. It requires studies to be performed that indicate whether the material is effective against the intended pest and safe to use. During the registration process, a pesticide label is created which contains directions for the proper use of the material. Use inconsistent with the label is illegal and considered pesticide misuse.

Since before 500 BC, humans have used pesticides to prevent damage to their crops. The first known pesticide was sulfur. By the 15th century, toxic chemicals such as arsenic, mercury and lead were being applied to crops to kill pests. In the 17th century, nicotine sulfate was extracted from tobacco leaves for use as an insecticide. The 19th century saw the introduction of two more natural pesticides, pyrethrum which is derived from crysanthemums, and rotenone which is derived from the roots of tropical legumes.

The U.S Environmental Protection Agency (EPA) defines a pesticide as "any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest".

Dahlia is a genus of bushy, summer- and autumn-flowering, tuberous perennials that are originally from Mexico, where they are the national flower.