Chlorine content of soil treated for three years with halogenated fumigants

Abstract

Experiments on the chemical control of Meloidogyne incognita (Kofoid et Whide) Chitwood attacking tobacco (Nicotiana tabacum L. cv. Erzegovina) were undertaken in 1969 in the province of Lecce, Southern Italy (Lamberti 1969 and 1971). Out of the 10 chemicals applied as soil treatments, including granular and liquid formulations, only three treatments provided sufficiently high levels of control to be considered economic. These were: Vorlex 201 (methylisothiocyanate 17%, chloropicrin 15%, 1,3 dichloropropene 1,2 dichloropropane 68%) applied at the rate of 300 l/ha; Di-Trapex (methylisothiocyanate 20%, 1,3 dichloropropene 1,2 dichloropropane 80%) applied at 300 l/ha and D-D (1,3 dichloropropene 1,2 dichloropropane 100%) applied at 150 l/ha. For commercial use it would be helpful and more economic if the nematicides had some residual effect against Meloidogyne spp. This was investigated in a further experiment but Vorlex 201 was omitted because at that time it was still in the experimental stage and had not been approved for commercial use. Although D-D or Di-Trapex were found to have residual effects persisting for up to three years, it is considered that the greater benefits are obtained by annual applications, but at lower dosage levels than the single application (Lamberti in preparation). However, successive annual application does raise the problem of excessive accumulation of chlorine in the soil to a level which may be phytotoxic to tobacco. The amonut of soluble chlorine salts in the soil following various applications of Di-Trapex or D-D (Table II), was therefore investigated.