Cultural Practices for Root-Knot Control


 It is commonly observed that root-knot on cigar-wrapper to-
 bacco is more severe on light sandy soil than on heavier soil.
 Wherever there is a choice of soil suitable for shades the heavier
 soil is usually planted, partly for this reason. The difference
 in severity of root-knot is explained by the fact that the lighter
 the soil the more readily the larvae can travel to reach the host
 plant (6).
 Although the experimental work was conducted on fine sandy
 loams, it would be logical to suppose that the effects of heat
 and drying in killing nematodes would be greater in a lighter
 soil. On the other hand, depletion of organic matter might be
 more serious, unless this can be offset by cover crops of oats
 and heavy application of stable manure.
 The effects of clean fallow will be studied further in connec-
 tion with an experiment now in progress on 2-year rotations
 for root-knot control. In this experiment tobacco is rotated
 with various other crops, including native weeds and grasses
 as well as cultivated crops. As a check on the 2-year rotations,
 1 treatment is continuous tobacco, followed each year by clean
 fallow and then oats, corresponding to Treatment 3 of the pre-
 vious experiment.
 SUMMARY
 Experiments were conducted on the effect of certain fall cul-
tural practices for root-knot control in a cigar-wrapper tobacco
shade, beginning with soil heavily infested after the 15th con-
secutive crop of shade tobacco had been harvested from the
field. The various treatments were applied from July to January
of each crop year, after which all plots were treated exactly
alike until the end of the harvesting season in July.
 Clean fallow, maintained by frequent listing of the soil,
followed in October by a cover crop of oats, gave the most con-
sistently good results of the treatments tried. The results of
this treatment were used each year as a basis for evaluating
the results of other treatments.
 Clean fallow for the entire 6-month period gave slightly less
root-knot than clean fallow followed by a cover crop of oats
but about the same quality; the yield was higher for the first
year only and then steadily declined, due probably to a gradual
first listing is to be made not later than 10 days after completion of harvest
and subsequent listing at intervals of not less than 7 days and not more
than 15 days apart."-AAA Handbook for Florida for 1942. U. S. D. A.
Agricultural Adjustment Administration, 1941, p. 14.