Gojilrol /:? 



Another recent nemotocide, also in the class of teTrmoivsry soil sterilsnts 

 nnd commercially available, is ^tylnne Q^V under the Crr^.r brand of the 

 Carbide and Carbon Chemicals Company, a Division of the Union Carbide 

 ajid Carbon Corporation. Mylnne is marketed as a dust or as a wettable 

 powder and is identified chemicallv as 3i'?-dimethyltetrahydro-l,3-3,2H 

 thiadiazine-2-thione. 



Some other recent developments have been initiated by the Dow Chemical 

 Comppny. The introduction to commercial use in 1957 of Telone, the 

 trademark name for a liquid fumigant composed of undiluted technical 

 dichlcropropenes and containing no bromine materials. Also, tliere vras 

 commercial use at this same time of Dorlone, the trademark name for a 

 mixture of two nematocides (Telone 75.2^ and Dowfume W-85 (EDB) 2U.8^ 

 by weight). This was in response to the observations that tinder various 

 soil and environmental conditions the present day soil fumigants exhibit 

 varying degrees of effectiveness in controlling different species of 

 plsjit-parasitic nematodes. At the present time, several other promising 

 chemicals are under test, but have not been placed on the market yet. 



Thus, commercial soil fumigation in the United States began in 1937, ".nd 

 the greater part of the development to its present status as a multi- 

 million dollor business has taken place since 19h5' The gradual develop- 

 ment of new materials, permitting new ways of application, broader 

 lethalness for use as temporary soil sterilants or limited phy to toxicity 

 for use on and around living plants, is greatly expanding the usefulness 

 of chemicals for nematode control. 



Basic Principles 



Most nematocides are used for control of nematodes in soil before 

 planting, and this situation ifri.ll be discussed first. Since plant- 

 parasitic nematodes feed only on living plants, they must be killed 

 by "contact" rather than "stomach" poisons. Also, movements of nema- 

 todes in soil are slow and limited in extent, which means that the 

 poison must be distributed throughout the soil. ■.iJhere annual crops 

 have been grown, the nematodes will be in the upper 15 to 18 inches of 

 soil, 1-ri.th the grr;ater part of the population in the upper 12 inches, 

 nematodes in the soil may be in the form of eggs, larvae, or adults; 

 but, in any case, will be surroimded by a thin film of water. In 

 certain cases, they may be further protected as cysts ( Heterodera ) , or 

 the gelatinous mediurii of egg masses ( Meloidogyne ) > or m?.y be in more or 

 less decomposed plant material. 



Nematodes have a cuticle which is of a lipoidal nature and impermeable 

 to many substances. 



\-ihen. these various fncts are considered, it is evident that the require- 

 ments for a soil nemntoeide are: 1) It must thoroughly permeate or be 

 mixed with the roil at least as deep as 12 inches and perhrps as deep 

 as 18 inches. 2) It must be able to penetrate the various barriers 

 fjurroundinp the ncmato'lns, eysts, pl-uit material, or at the veiy least. 



