Featured Insect

While the exact genus of aphid responsible for the blight is still debated, it is most commonly believed to have been Daktulosphaira vitifoliae, or the grape phylloxera. In appearance they are six-legged, oval-shaped ( pear-shaped if they lay eggs), and nearly microscopic, measuring about 0.04 inches long and 0.02 inches wide. (Nymphs resemble adults, but are even smaller.) Their coloration varies from yellow, to yellowish-green, olive green, brown, light brown, to orange [5.] Due to their small size, phylloxera usually make themselves obvious due to the presence of galls—yellowish-green, wart-like growths found on grape leaves—rather than the insects themselves. However, such galls are typically only seen on the leaves of American grape varieties. During the blight, phylloxera mainly infested European roots. In America, they will still winter on roots, but this causes far less damage. After all, these aphids are native to Southern and Eastern North America, and the continent’s grape vines evolved alongside them. The pest was only introduced to the rest of the world by accident—to the detriment of countless vintners. Ever since, phylloxera have made their way to practically every place grapes are grown, including Europe, Australia, New Zealand, South Africa, South America, and the rest of North America.

Above: An extreme close-up of an adult phylloxera.

Its life cycle is a complicated process, featuring up to 18 different stages, and for the purposes of this section, it will have to be somewhat simplified. To begin with, its life cycle may be separated into four principal forms: a wingless sexual form, a wingless leaf-galling form, a wingless root-feeding form, and finally, a winged form [6.] The following is a condensed form of the phylloxera’s life cycle. First, there is the sexual form, in which male and female eggs are laid under young grape leaves. Once hatched, lacking digestive systems or mouths, they mate and die. Before the female dies, however, she lays a winter egg in the bark of the plant’s trunk, which then develops into the leaf form. The resulting nymph climbs onto another leaf, forms a gall by injecting her saliva into it, and then parthenogenetically (essentially, asexually) lays eggs into said gall. Adult phylloxera can lay as many as 200 eggs per cycle [7.]

Above: A simplified version of grape phylloxera's life cycle.

More nymphs hatch from these eggs, at which point, they may either move to other leaves or to the roots, which begins the root form. Seeking nourishment, they pierce the roots and suck the sap, which is their main diet. In this process, they also secrete a poison that prevents the root from healing properly. These deformations, “nodosities” and “tuberosities,” as well as resulting fungal infections, gradually kill the roots before eventually killing the entire vine. (This process is what caused the Great French Wine Blight.) For the next several summers (up to seven), this nymph will lay eggs, spreading the infestation to other roots of the same vine, or a different vine. (Nymphs that hatch in Autumn will hibernate over the Winter, before emerging the following Spring as the sap begins to rise.) Finally, there is the winged form. This occurs during the late Summer in especially humid areas, and not all nymphs go through it. Nonetheless, these nymphs (wingless ones, as well) restart the cycle by laying male and female eggs on the underside of new leaves [8.]

Above: An example of a phylloxera-damaged graperoot.

Interestingly, there are regions within these countries or continents that have remained untouched by the epidemic. For example, dryer areas or those with sandy soils were spared. In other cases, swift government mandates forbidding the transfer of equipment and vines between areas saved the day. (Specifically, Australia took such a course of action with the Vine Protection Act of 1874. Even now, Western Australia and Tasmania have never been infested [9.]) In other cases, however, certain vineyards have gone unscathed for no apparent reason—even in France during the time of the blight. As such, even though the majority of current grape vines feature grafted roots, there are still some varieties where this is not the case. Since there is no actual cure, chemical or otherwise, for phylloxera infestation, there is a chance that these vineyards’ luck will run out someday.