Florida Agricultural Experiment Station


Under favorable conditions these eggs hatch into larvae, which
remain within the same root or migrate through the soil and
infect other roots. Newly hatched larvae are slender and about
1/50 inch long, too small to be seen with the naked eye. Mature
egg-laying females are pear-shaped or nearly round, and their
bodies are about 1/30 inch in diameter or about the size of the
period at the end of this sentence. They can be seen as pearly
white bodies when an old gall is broken or crushed (Fig. 4).

 REVIEW OF LITERATURE
 Conditions such as temperature, moisture and aeration, as
they affect the development of root-knot nematodes, have been
studied by many investigators. A few findings of most interest
to the present study will be mentioned here.
 Nematodes develop at any temperature between 500 and 900
F.; at the most favorable temperature, about 810, the time re-
quired for a complete generation is 23 to 36 days. Above 810
activity is reduced. Freezing at 320 does not kill larvae, a tem-
perature of 0 for 2 hours being required (6)2.
 All larvae are killed at 1040 in about 2 hours and at 1090 in
 8 minutes; eggs in masses survive for 41/2 days at 104 (3).
 Nematodes are active throughout a wide range of moisture
 conditions, from wet to fairly dry. Whenever soil in the field
 becomes extremely dry nematodes unprotected by living roots
 are rather easily killed; normally, however, only the uppermost
 layer of the soil becomes dry enough to kill the nematode (7).
 The soil atmosphere below the dry surface layer is saturated with
 water vapor, and this condition favors the long-continued sur-
 vival of the larvae, because they are not so active as to deplete
 their store of reserve energy (6).
 Aeration of the soil is favorable to hatching of the eggs;
 a crust on the soil reduces aeration and delays hatching (7).
 After the eggs hatch if no susceptible plants are available the
 larvae gradually exhaust themselves and die. Larvae are more
 susceptible than eggs to killing by various adverse conditions.
 Several instances have been reported where cultural practices
 have been found effective for root-knot control on field crops.
 The Georgia Coastal Plain Experiment Station (2) recom-
 mended fall cultural and sanitary practices for root-knot control
 in flue-cured tobacco. These practices included "the plowing
 2 Italic figures in parentheses refer to "Literature Cited" in the back
 of this bulletin.