Bulletin 151, Truck and Garden Insects


dosage to be given as well as the depth of the hole will depend
upon the size and depth of the nest. As soon as the liquid has
soaked away, cover up the hole with dirt and tramp it solid.
The gas given off will penetrate the galleries of the nest and
kill most of the ants and their young. It is best to do this in
the early morning when most of the ants are at home." All
of the nests within 50 or 60 feet of the seed bed should be
treated. As recorded under the head of fumigation, cyanide is
one of the most powerful poisons known, either when inhaled
or swallowed. It should also be kept out of open sores. Some
ants will probably escape the first treatment. These will, how-
ever, lose all interest in the seed bed and will go slowly about,
cleaning the dead ants out the nest. Their slow and languid
motions are in sharp contrast to their feverish activity of the
previous day. The survivors will probably, in the course of a
few days, start small new nests in the vicinity. These in turn
may be treated.
 ROOT-KNOT (Heterodera radicicola)
 This is a disease characterized by knot-like swellings on
the roots. Severely infected plants fail to make proper growth
and often turn yellow and die prematurely.
 The cause is a minute round-worm or nematode which bores
into the roots to feed. It gives off a poison which causes the
plant to make the swelling. It affects nearly all garden and
truck crops, except corn, to a varying degree. The worms are
not very active during the winter, but during the warmer
weather from April to October they often make it impossible
to grow a profitable crop of certain plants on the infested land.
Newly-cleared land is usually free from these worms, but most
sandy soils of Florida, when cleared and cultivated for a num-
ber of years, become infested.
 Control*.-The usual way to free infested land is to raise
 only non-susceptible crops on it for three years and thus starve
 out the worms. Among such immune or partly immune plants,
 are, most of the true grasses, including crab-grass and Bermuda,
 most varieties of corn and wheat, rye, and some varieties of
 oats; velvet beans, and beggarweed, Iron and. Brabham cow-
 peas are usually resistant. Onions, parsnips, strawberries and
 turnips are but slightly affected. While growing any of these
 crops to free the land of nematodes it is important that weeds
 should not be allowed to grow there as the nematodes are
 *See page 201, Other Means of Controlling Root-Knot.