Potato Beetle
Aiton's Encyclopedia (1910)
Important: Safety Warning
This page recommends pest-control substances such as arsenic compounds, strychnine, or cyanide — in some cases applied to food crops. These substances are lethal to humans and animals, and their use is now banned or strictly controlled.
This information has been left in for historical purposes but should not be acted upon.
an insect pest, popularly but less correctly called potato "bug." The potato beetle is called decemlineatus, or ten-striped, by entomologists. When first known the Colorado potato beetle dwelt along the eastern base of the Rocky Mountains , feeding on the leaves of a wild, spiny ground cherry that belongs to the potato family and is called locally a "sand-bur." In 1856 this beetle fell upon a field of potatoes 100 miles west of Omaha. It journeyed steadily eastward, and by 1874 it had extended its ravages to the Atlantic. C. V. Riley, the noted entomologist, says, "It never quits a locality when it obtains a foothold." The adult beetle passes the winter in the ground and in the spring flies about on broad, rose-colored wings until it finds young potato tops. It even burrows into the potato hills to meet the rising sprouts half way. As soon as the young tops appear the female attaches a cluster of twenty to forty oval orange-colored eggs to the under side of a leaf. In the course of a week tiny hump-backed larvae of a venetian red color appear and betake themselves to feeding vigorously on the leaves of the plant. They have a faculty of climbing to the very tip of the growing stalk where the young leaf is tenderest. As the larva grows older it becomes paler in color and its sides are marked by two rows of black spots. In about three weeks it enters the ground and makes a burrow in which it remains for a few days, emerging a perfect beetle with striped wing covers. From egg to beetle is a period of four to six weeks. The female beetle lays 400 or 500 eggs in a season, and, under favorable circumstances, the fourth generation, great grandchildren, mature into adults before winter. The adults burrow in loose soil to spend the winter. Fowls are not fond of potato beetles. Young ducks are most apt to help in the potato field. The rose-breasted grosbeak devours enormous quantities, and the garden toad eats so many that he can hardly move. Other beetles attack the larvae. The only effectual means, however, of defending a large field of potatoes lies in spraying with paris green , or some similar drug, mixed in the proportion of a table-spoonful to three gallons of water. The larvae as well as the beetles are poisoned by eating bits of leaf with "green" on it and die ignobly. Spraying is an effective, inexpensive means of protection, from which no evil effects on the potatoes have been noted in many years. See Potato ; Spraying ; Beetle ; Paris Green
What Has Changed in the Last Century
Aiton's confidence in 1910 that spraying paris green did the job "from which no evil effects on the potatoes have been noted" is exactly what has not survived: arsenical sprays were abandoned in the 1940s and 1950s, and the arsenic-residue scandals of that era helped build the case for modern pesticide regulation. Leptinotarsa decemlineata then became the textbook case of resistance, defeating DDT within a few years of its introduction and going on to shrug off dozens of insecticide classes, including the neonicotinoid imidacloprid. The beetle also went global after 1910, becoming established in France in the 1920s and spreading across Europe and into Asia after the Second World War, so Riley's remark that "it never quits a locality when it obtains a foothold" now applies to a continent it had never reached. In 2023 the US EPA approved Calantha, a sprayable RNA-interference product designed to silence one of the beetle's own genes — the first pesticide of its kind, and aimed at this very insect.
Written for this edition, 2026.