Cultural Practices for Root-Knot Control


Fig. 7.-Abnormal tobacco root system, grown after a cover crop of native
 vegetation (right); normal root system (left).

 condition which disappeared before the end of the tobacco grow-
 ing season. The decomposition of the grass may also have
 caused the reduction in root-knot index for certain years, as
 was demonstrated for a coarse grass (Panicum barbinode Trin.,
 Para grass) by Linford, Yap and Oliveira (5). Results of this
 experiment might have been quite different if the cover crop
 had been turned under a month or 2 earlier.
 Nematode control obtained by clean fallow under the condi-
tions of this experiment was probably due to a combination of
4 separate factors, which are listed and discussed.
 1. Aeration.-Cultivation supplies oxygen to the soil, pro-
viding conditions more favorable to the hatching of nematode
eggs than in soil allowed to become crusted and deficient in
oxygen (7). Larvae are more susceptible than eggs to killing
by other factors to be mentioned.
 2. Starvation.-To obtain most effective control of nematodes
by starvation, according to Tyler (6), weeds must be destroyed
every 10 days in warm weather, to keep the worms from matur-
ing and producing eggs; the interval between plowings may
gradually be lengthened to a month or 2 in cold weather. Since
rain often interferes with the plowing schedule it is probably