28 
FLORIDA STATE HORTICULTURAL SOCIETY. 
most of the garden vegetables, especially 
cucumber, squash, pumpkin, water and 
muskmelon. On the other hand, the in¬ 
jury has been but slight in those cases 
where I have observed it on the follow¬ 
ing : various grasses, as Bermuda, crow¬ 
foot, fescue, orchard grass, German millet, 
persimmon, sawbrier, wormseed, chufa, 
bush-clover, etc. I have yet to see a case 
of true root-knot on any of the citrus 
trees, velvet-bean, Florida beggar-weed, 
oats, rye, barley, sorgum, hog-millet, etc. 
Many ideas have been advanced as to 
how this pest should be combated but 
many of them are based on experiments 
made with the closely related sugarbeet 
nematode of Germany. But little actual 
experimental work has been done. One 
method is that of soil sterilization, i. e. 
freeing the soil of the noxious organism 
l)y direct means. I shall mention various 
suggested means of doing this. 
Chemical Means.—The most efficient 
of these is the use of carbon bisulphide in¬ 
jected into the soil to a depth of several 
inches at close intervals and allowed to 
diffuse there throughout the soil. If 
enough is used this is effective. It has 
several serious objections; it is expensive, 
so expensive in fact, that it would proba¬ 
bly take several hundred dollars worth 
to treat one acre, not to speak of the labor 
of applying it. It is also poisonous to 
roots. A large fig tree will stand it some¬ 
times, but the check to the growth is great. 
It is highly inflammable. It does not 
mix with water, and so cannot be used in 
wet soil. Formalin in dilute solution is 
equally effective if applied in sufficient 
quantity. However, to wet dry soil to 
the depth of a foot would require about 
five gallons of solution to a square yard 
costing $150 to $200 per acre. My ex- 
])eriments to determine whether a lesser 
quantity will be sufficient are now under 
way. This solution is also harmful to 
vegetation, but if kept from the growing 
part of the plant is not as injurious as 
carbonbisulphide. Lime, gas-lime, gas 
liquor, oils, etc., have been tried on the 
sugar-beet nematode without effect. I 
am now trying some of them on the root- 
knot. 
Heat is the most efficient means yet 
found for killing out all kinds of pests, 
including the root-knot nematode. 
Thanks to Stone and Smith in Massachu¬ 
setts, the problem has been settled as far 
as nematodes in green-houses are con¬ 
cerned. Steam is passed at high pressure 
through tiles or perforated iron pipes run¬ 
ning through the soil. This effectually 
kills all animal and fungous parasites. 
It seems doubtful whether that method 
will ever become of use in the open, unless 
it be for seed-beds or for truck farms 
where the income is very high. It would 
probably cost not less than $2,000 per 
acre to establish such a ster’fizing appara¬ 
tus. The often recommended building of 
large fires upon the spot to be sterilized 
is to be discouraged, for the injury to the 
soil is too great. 
Freezing, formerly supposed to be fatal 
to the root-knot nematode, is considered 
so by me no longer since I obtained 
authentic record of peonv plants going- 
through a winter temperature of 35 de¬ 
crees below zero without even a mulch 
o 
protection and showing root-knot again 
that summer. That was not in Florida 
In Java where the dry season is well 
marked and is really dry, it has been 
found possible to exterminate the root- 
knot nematode by drying out the soil. 
This is done by keeping it in fine tilth 
during the whole dry season by means 
of repeated plowings, and harrowings. 
