CHERRYFIELD — The history of efforts by Maine’s blueberry growers to control the blueberry fruit fly began almost 70 years ago and originally involved agricultural practices that today would be regarded as “organic.”

Most of the insect damage to blueberry plants happens during the vegetative phase of the blueberry plant’s development, when the new leaves are chewed by the larvae of the spanworm moth. Severe spanworm infestation can limit the development of the fruit buds that will produce the next year’s blueberry crop.

Later during the growth season, another insect pest is waiting for the “set” of last year’s fruit buds and the development of the mature berry. This is a small black fly with banded wings that lays its eggs in the ripening blueberries. It was the “maggot” or larva of the blueberry fruit fly, white and worm-like in appearance, for which inspectors in all of Washington County’s blueberry-packing plants were searching as early as 1922.

According to a 1963 publication by the University of Maine Press titled “University of Maine Series, No. 78,” concern about the blueberry fruit fly did not become widespread until after World War I.

At that time, the life cycle of the blueberry fruit fly already had been studied by scientists at the Maine Agricultural Experiment Station. Of many recommendations given by scientists to blueberry growers during the early 1920s, the most important was to burn the fields completely to interrupt the fruit fly’s life cycle by destroying the insect in its pupal stage in the ground.

The burning of blueberry fields after the harvest, which serves to prune the plants and stimulate new growth, was a common practice in Maine as early as the 18th century. The spreading of hay or straw as a fuel to help carry the fire, a practice that became common during the 1920s, is still employed on small commercial fields.

Later came a different strategy aimed at the adult fruit fly. Experiments conducted in Washington County during a five-year period in the 1920s by the U.S. Bureau of Entomology revealed that the fruit fly could be controlled effectively by “dusting” the fields with a dry chemical compound containing arsenic. “Dust mills” were set up in the county. The practice of dusting the crop before the August harvest became a common one and was still employed during the early 1960s.

Much of the scientific investigation of the life cycle of the fruit fly was directed by the late Dr. Frank H. Lathrop, a native of South Carolina. Lathrop worked originally as the senior entomologist with the federal Bureau of Entomology. Later, for many years, Lathrop lived in Orono and served as an entomologist with the Maine Agricultural Experiment Station.

To be effective, the application of pesticides must take place after the fruit fly has emerged from its dormant, pupal stage in the ground and before the female has laid eggs in the ripening blueberries. The pesticide-vulnerable stage in the fly’s life cycle occurs during the season when other food crops, which could accidentally receive drifting pesticide spray, are ripening in gardens.