A Manual of Horticulture for the State of Idaho (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...root insect (an unknown number of generations throughout the year); nymphs, which become winged insects (one generation in midsummer). The gall stage may be admitted, as it generally is in California, and insects which hatch from the fertilized eggs laid by the female go directly to the root and produce offspring, which are indistinguishable from the root form produced in the normal cycle. For how many generations the root form can exist and reproduce without the invigoration supposed to come from the production of the sexual form is not known, but certainly for four years and probably more. All forms of the phylloxera are extremely minute, the root form being about one-twenty-fifth of an inch long when it reaches the adult egg-laying state, and little more than half this length when young and active. It is just large enough to be seen by the unaided eye in a good light when its appearance is known, and, by the help of a glass magnifying five diameters, its legs and antennae are plainly visible. Its color is light greenish yellow in summer, and somewhat darker in winter; so that when numerous attacked roots appear as though dusted in spots with powdered mustard or cinnamon. The newly hatched insect is fairly active, and at first moves about from place to place on the roots; but finally, when it reaches the egglaying stage, it inserts its sucking-tube into the root and remains fixed. Nature Of Injury.--The amount of nutriment taken from the vine by such minute insects, even when present in the immense numbers in which they sometimes occur, is not sufficient to account for the disastrous effect upon the plant. The death of the vine is due to the decay which sets in wherever the phylloxera has attacked the roots. Wherever a phylloxera inserts its sucking-tube ...