December 4, 2010
Today when the gardening crew came to lay down more decomposed granite in the front yard of our Mt Washington offices, I noticed this Scale Insect on several twigs of the California Black Walnut sapling that grew in the Devil’s Strip next to the fence. When I went back to take the photograph, it had been pruned and left in the street by Paco the Gardener. I took the photographs. These Scale insects look suspiciously like the Cottony Cushion Scale, Icerya purchasi, (See BugGuide) that was introduced from Australia and nearly devastated the citrus crop after its introduction in around 1868.
This identification is going to be our top priority as we are quite committed to saving the endangered California Black Walnut in Southern California, and most aggressively in the Mt Washington neighborhood of Los Angeles.
Update: December 5, 2010
An internet search turned up a Google Book entry on Pests of Crops in Warmer Climates and Their Control by D.S. Hill and it indicates that the Cottony Cushion Scale can be found on English Walnut, Juglans regia, so it might be safe to assume that it may also be found on California Black Walnut, Juglans californica.
Clare Marter Kenyon wrote
ugh. no. i don’t recall seeing this scale on juglans californica…
get rid of it pronto!