The vine has been attacked by the Oidium Tuckeri, the Phylloxera vastatrix and the Peronospora viticola, which in rapid succession wrought great havoc in Italian vineyards.
Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
Oidium or mildew is only second in importance to the phylloxera.
The Alto Douro has from time to time been sadly ravaged by the oidium and phylloxera.
Since then oidium has reappeared from time to time, but the remedy of spraying with finely divided sulphur, which was discovered at the time of the epidemic, has enabled the wine farmers to keep it under.
The bush vines of this region are more exposed to the attacks of Oidium Tuckeri, which invaded the country in 1851, and of Phylloxera vastatrix, which followed in 1863, than the more deeply-rooted vines trained on trellises or trees.
The former also looks on the ordinary disjointing bacterial cell as an oidium, and it must be admitted that since Brefeld's discovery of the frequency of minute oidia and chlamydospores among the fungi, the probability that some so-called bacteria - and this applies especially to the branching forms accepted by some bacteriologists - are merely reduced fungi is increased.