12 DEPARTMENT OF AGRICULTURE 4

bacterial nodules may be mistaken for root-knot galls, but they usually
are easily distinguished from knots caused by root-knot nematodes by
the fact that they are mostly fixed on a short peduncle and hang on th|
side of a root whereas the swelling caused by root-knot nematodes is
most often an axial one of the. root proper (Fig. 9), (4) there arl
certain plants that have normally knotted or swollen roots (e.g. Parthe
nocissus sp.). Thus it is evident that even this common root-knot nemi
tode disease must be diagnosed by the presence of the organism itself
rather than through the occurrence of knots of one kind or another o
the roots.


 Figure 6.-A. Root-knot infected sweet potatoes; the sweet potato to the leftI
exhibits cracking which appears to result in certain instances from a root-knot infec-
tion. B. Beet heavily infected and disfigured by root-knot nematodes. C. Carrot
disfigured and made unmarketable by root-knot nematodes; 1/2 normal size.