Grapevine flavescence doré phytoplasma
Flavescence dorée affects only vinifera grapes and interspecific hybrids. Labrusca cultivars are resistant. Symptoms usually appear the year after infection and either get progressively worse until the vine dies or disappear in an apparent recovery. Symptoms include delayed or no bud break and progressively shortened internodes. In summer, vines take on a weeping posture, and shoots become rubbery and fail to lignify. Characteristic black pustules may be seen in longitudinal rows near the bases of shoots. The leaves have golden yellow or reddish patches and curl downward. Growing points become necrotic, and flower and fruit clusters shrivel up and fall. The pathogen overwinters in infected canes and is spread by a leafhopper. Symptoms may resemble those of certain virus diseases or potato leafhopper damage.