Fusarium wilt and bacterial wilt are untreatable, fatal fungal diseases that cause cucumber plants to wilt and die. Symptoms may include white mold on the vines, stunted growth and discolored roots. Bacterial wilt is carried by cucumber beetles, which transmit the disease from infected plants to healthy plants. Because fusarium wilt can live in the soil long after the infected plant has been removed, the only way to avoid it is to plant resistant cultivars.