Three species of true firs in the Pacific Northwest--Abies gran-dis, grand fir; A. amabilis, Pacific silver fir; and A. lasiocarpa,
subalpine fir--are severely damaged or killed by an imported insect
pest, the balsam woolly aphid (Chermes (Adelges) piceae Ratz.), Infestations of this insect cause abnormalities in the wood and, in...
Knowledge of the viruses which are mechanically transmitted
from pear to herbaceous plants and the diseases they cause in pear
is not complete. This thesis discusses the means used to mechanically
transmit pear viruses, the properties of those viruses and their
relationships with latent viruses of apple.
Herbaceous plant virus...