The female phylloxera is yellow and about 1 mm/0.039 in long. Typically surrounded by masses of eggs, it is barely visible to the naked eye as it feeds on the roots. There are four to seven generations in the summer, each producing females capable of laying more eggs. As the eggs hatch, so-called ‘crawlers’ move to other roots of the vine, and some climb the trunk and can spread to other vines, or even vineyards, by the action of wind or machinery dislodging them from the foliage. Because of the movement of the crawlers through soil cracks, phylloxera tends to spread in a circle from the original infected vine. Wind-blown crawlers create secondary infections downwind.
