A method is described for the control of nematodes and soil-borne insects in agricultural crops which comprises applying to the situs of infestation a composition containing as active ingredient a compound of the formulaR--Z--(CH.sub.2).sub.n --Qwherein R is an alkyl radical of one or two carbon atoms carrying one-to-four fluorine substituents and one-to-three chlorine or bromine substituents represented as CF.sub.p X.sub.(3-p) -- or CF.sub.r X.sub.(3-r) --CF.sub.s X.sub.(2-s) --; Z is --(CH.sub.2 --CHX)-- or --(CH.dbd.CH)--; X is chlorine or bromine; Q is methyl, isopropyl, tert-butyl, or C.sub.3 -C.sub.6 cycloalkyl; n is 5 to 12 as required to yield in the compound a chain of 10 to 16 carbon atoms; p is 1 or 2; r is 2 or 3; s is 0 or 1 or 2. A process for preparation of active ingredient compounds is described, and utility of compositions against nematodes and soil-borne insects is exemplified.