. Fig. 76.—The narcissus stem nematode, with young worms and eggs. (Enlarged nearly 150 times.) (From Ext. Cir. 118.) causes the development of galls, swellings, and other abnormal growths and eventually weakens or even kills the host plant. These effects are similar to those often produced by fungi and bacteria and, since the causative organism is invisible to the eye, may properly be classed as diseases. Nematodes reproduce by means of eggs which become abundant in diseased plant parts and in infested soil. The eggs average about ^50 inch in length and hatch into young worms of a length of a
. Fig. 76.—The narcissus stem nematode, with young worms and eggs. (Enlarged nearly 150 times.) (From Ext. Cir. 118.) causes the development of galls, swellings, and other abnormal growths and eventually weakens or even kills the host plant. These effects are similar to those often produced by fungi and bacteria and, since the causative organism is invisible to the eye, may properly be classed as diseases. Nematodes reproduce by means of eggs which become abundant in diseased plant parts and in infested soil. The eggs average about ^50 inch in length and hatch into young worms of a length of about %2 i^ich (fig 76). These again attack plants when favorable conditions and hosts are available. The root-knot, or common garden, nematode, Heterodera marioni,*' causes swellings or galls on the roots of a great many different kinds of plants, including most annual crops, fruit trees, ornamentals, and many weeds. The worms are imbedded in these galls, the largest form being the *2For further information, see: Tyler, Jocelyn. The root-knot nematode. Cali- fornia Agr. Exp. Sta. Cir. 330:1-34. 1933.
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