954 
Journal of Agricultural Research voi. xxvn, No. i* 
The causal organism (Tylenchus tritici) is a minute nematode and may 
be found in great numbers in the larval state inside the mature galls. 
From 2,000 to 20,000 or more larvae are found in one gall. They are 
slender, threadlike, round worms nearly 1,000 m in length and 25 ii in 
width. Escaping from the disintegrating gall into the soil, they reach 
the growing point of the host plant where they remain ectoparasitically 
until the flower parts begin to form, when they cause the formation of 
galls in place of kernels. Inside of these galls the larvae develop into 
male and female adults. Each female may produce several thousand 
eggs, which in a short time hatch into larvae. These larvae go into a 
dry, dormant state in the mature gall, and in this condition they can 
remain alive more than 10 years. They can endure extremely low tem¬ 
peratures and considerable desiccation, but immersion in water at 56° C. 
for 5 minutes kills them. They are resistant to chemicals, so that the 
latter are ineffective in seed treatment in concentrations that will not 
injure the seed. Although not so resistant to unfavorable conditions 
when outside of the protective galls, nevertheless in a dried dormant 
condition they are able to remain alive for several years. Larvae that 
have been in the free-living state for some time, in the soil or between 
the leaf sheaths of plants, succumb more readily to unfavorable condi¬ 
tions than those remaining in a dHed dormant condition. 
The disease is most commonly spread by means of infested seed and 
straw. It may be carried from one farm to another by the threshing 
machine. Screenings from infested wheat may also carry the disease 
to a new area. Other possible agencies of dissemination are farm imple¬ 
ments, the feet of animals moving from infested to clean soil, barnyard 
manure from infested straw, and running surface water. Birds are of 
minor importance as agencies of distribution. 
Through their own efforts, the larvae were unable to effect a general 
invasion of the wheat at a distance of more than 4 inches (10 cm.) laterally 
although a few reached plants 12 inches (30 cm.) distant. Vertically, 
they moved from 12 inches below the seed and produced infection. 
The organisms invade the plant after the loosening of the coleoptile, 
and presumably invasion may continue until elongation of the culm 
occurs. 
The organisms may overwinter within the protective galls or in a free- 
living state in the soil or between the leaf sheaths of the host plants. 
The disease is easily controlled by the use of clean seed sown on clean 
soil* Susceptible cereals should be kept off infested fields for at least 
one year, as this will starve the nematodes in the soil. 
literature cited 
(1) APPIy, J. 
1913. die radekornkrankheit D £ S weizens. Wiener Landw. Ztg. 63:787, 
illus. 
(2) Averna-Sacca, R. 
1912. RELATORlO DO GABINETE DE PATHOLOGIA VEGETAL, DE MAIO A 31 DE 
dezembro DE 1911. Bol. Agr. [Sao Paulo] 13:208-246, illus. 
(3) Bastian, H. C. 
1866. monograph on the anguiixuudae. Trans. Linn. Soc. London 25: 
73-184, illus. 
( 4 ) Bessey, E. A. 
1905. a nematode disease OF grasses. Science (n. s.) 21:391-392. 
