COTTONY CUSHION SCALE

Cottony-cushion scale, Icerya purchasi, a serious threat to citrus and fruit trees, was discovered in California in the 1860s. By the 1880s its effect on the state’s citrus industry was devastating, until 1888 when California horticulture official, Albert Koebele, discovered the Australian ladybird, Rodolia cardinalis, known by the common name of vedalia, feed upon this scale insect. Live vedalia importation was in instant demand, and by 1890, the state’s infestation problem was quieted. On Santa Cruz Island, November 26, 1918 the superintendent wrote to the State Insectary in Sacramento:

“We are becoming rather badly troubled with cottony cushion scale and our spraying has had little or no effect in keeping it under control. We would like to make application for a colony of Novius cardinalis [vedalia] for delivery at the proper season.”

January 1, 1920 another letter was sent:

“Kindly let me know what procedure is necessary to procure a colony of Australian ladybirds for us against the cottony cushion scale. Many of the trees, brushes, and even alfalfa plants are badly infected.”

Sacramento replied they lacked the scale insect on which to raise the ladybirds, and therefore the island superintendent sent a supply of the scale in order to facilitate the raising of ladybirds for release the island.