Under normal conditions in warm climates many of the species are perennials, but, in the United States for example, climatic conditions necessitate the plants being renewed annually, and even in the tropics it is often found advisable to treat them as annuals to ensure the production of cotton of the best quality, to facilitate cultural operations, and to keep insect and fungoid pests in check.
The fungoid diseases of tobacco are comparatively unimportant; there are, however, some diseases of obscure origin which at times cause considerable damage.
C. Cooke, Fungoid Pests of Cultivated Plants; Thos.
So far the Hevea plantations in Ceylon and the East have not been seriously troubled by insect or fungoid pests, and those which have occurred have succumbed to proper treatment.
The most destructive form of fungoid disease 1.
The cells in which the fungoid organism is vigorously flourishing are exceedingly active, showing large size, brilliant nuclei, protoplasm and vacuole, all of which give signs of iptense metabolic activity.
P. alba suffers much from the ravages of wood-eating larvae, and also from fungoid growths, especially where the branches have been removed by pruning or accident.