A grindable solid resinous composition comprises an insecticide in a thermoset resin. The composition is prepared by p mixing the insecticide with the precursor of the thermosetting resin and then setting or curing the mixture by a catalyst, leaving for a period of time, heating or by exposure to ultra-violet irradiation. Specified thermosetting resins are (a) unsaturated alkyd resins prepared by condensing one or more unsaturated dibasic organic acids, e.g. maleic or phthalic acids or their anhydrides with one or more saturated or unsaturated glycols, e.g. propylene glycol, followed by blending with a monomeric unsaturated organic compound, e.g. styrene, a -methylstyrene, vinyl toluene, diallyl phthalate or methylmethacrylate, using as catalyst an organic peroxide such as benzoyl peroxide, ethyl methyl ketone peroxide, cyclohexanone peroxide or cumene hydroperoxide with or without an accelerator, e.g. cobalt or manganese napthenate; (b) the di-isocyanate-modified unsaturated alkydresins prepared as in (a) but using an organic di-isocyanate as blending agent; (c) epoxy resins prepared from a precursor which is a reaction product of a polyhydric alcohol or phenol with a halohydrin, e.g. epichlorohydrin or a diepoxy compound, e.g. butadiene dioxide using as catalyst a polyfunctional amine or amide, e.g. diethylenetriamine or diethylamino propylamine or one or more polybasic acids; (d) amino resins, e.g. "Cellobond" (Registered Trade Mark) prepared from precursors which are reaction products of formaldehyde with urea or melamine or both, the precursors of ethers of amino resins being prepared by a similar reaction employing an aliphatic monohydric alcohol of more than three carbon atoms, e.g. butanol. The precursor is cured by an acid catalyst; (e) phenolic resins, e.g. resoles and the ethers thereof prepared as in (d) using phenol, cresol, xyleneol or mixtures thereof instead of urea or melamine; and (f) the product obtained by curing the liquid polymer of an alkenyl phenol, e.g. obtained from cashew nut shell, with formaldehyde, formalin, hexamine or paraformaldehyde. The composition may also contain a filler, e.g. diatomaceous earth and may be formulated with a surface active agent. Specified insecticides are o,o-dimethyl-s-(1,2-dicarbethoxyethyl)-phosphorodithioate; o,o-diethyl-o-(2-isopropyl-4-methylpyrinidyl-6)-phosphorothioate; 2,3-p-dioxanedithiol-s,s-bis-(o,o-diethyl phosphorodithioate); o,o,o,o-tetraethyl-s,s-methylene-bis-(phosphorodithioate); o,o-diethyl-o-(2,4-dichlorophenyl)-phosphorothioate; o,o-diethyl-o-p-nitrophenylphosphorothioate; o,o-dimethyl-1,2-dibromo-2,2-dichloroethyl phosphate; o,o-dimethyl-2,2-dichlorovinyl phosphate; o,o-dimethyl-o-(3-chloro-4-nitrophenyl)-phosphorothioate; pyrethrins with or without a synergist, e.g. piperonylbutoxide; D.D.T; dieldrin and benzene hexachloride. The composition may contain other pesticides, e.g. miticides, acaricides, bactericides or nematocides providing they do not inhibit the setting of the resin.ALSO:A grindable solid resinous composition comprises an insecticide in a thermoset resin. The composition is prepared by mixing the insecticide with the precursor of the thermosetting resin and then setting or curing the mixture by a catylyst, leaving for a period of time, heating or by exposure to ultra-violet irradiation. Specified thermosetting resins are (a) unsaturated alkyd resins prepared by condensing one or more unsaturated dibasic organic acids e.g. maleic or phthalic acids or their anhydrides with one of more saturated or unsaturated glycols e.g. propylene glycol, followed by blending with a monomeric unsaturated organic compound e.g. styrene, a -methylstyrene, vinyl toluene, diallyl phthalate or methyl methacrylate, using as catalyst an organic peroxide such as benzoyl peroxide, ethyl methyl ketone peroxide, cyclohexanone peroxide or cumene hydroperoxide with or without an accelerator, e.g. cobalt or manganese naphthenate; (b) the di-isocyanate-modified unsaturated alkyd resins prepared as in (a) but using an organic di-isocyanate as blending agent; (c) epoxy resins prepared from a precursor which is a reaction product of a polyhydric alcohol or phenol with a halohydrin e.g. epichlorohydrin or a diepoxy compound e.g. butadiene dioxide using as catalyst a polyfunctional amine or amide e.g. diethylene triamine or diethylamino propylamine or one or more polybasic acids; (d) amino resins e.g. "Cello-bond" (Registered Trade Mark) prepared from precursors which are reaction products of formaldehyde with urea or malmine or both, the precursors of ethers of amino resins being prepared by a similar reaction employing an aliphatic monohydric alcohol of more than three carbon atoms e.g. butanol. The precursor is cured by an acid catalyst; (e) phenolic resins e.g. resoles and the ethers thereof prepared as in (d) using phenol, cresol, xyleneol or mixtures thereof instead of urea or melamine; and (f) the product obtained by curing the liquid polymer of an alkenyl phenol e.g. obtained from cashew nut shell, with formaldehyde, formalin, hexamine or paraformaldehyde. The composition may also contain a filler e.g. diatomaceus earth and may be formulated with a surface active agent. Specified insecticides are o, o-dimethyl-s-(1, 2-dicarbethoxyethyl)-phos-phorodithioate; o, o-diethyl-o-(2-isopropyl-4-methyl-pyrmidyl-6)-phosphorothioate; 2, 3-p-dioxanedithiol-s, s-bis-(o, o-diethylphosphorodithioate); o, o, o, o-tetraethyl-s, s-methylene-bis-(phosphoro-dithioate); o, o-diethyl-o-(2, 4-dichlorophenyl)-phosphorothioate; o,o-diethyl-o-p-nitrophenyl phosphorothioate; o, o-dimethyl-1, 2-dibromo-2, 2-dichloroethyl phosphate; o, o-dimethyl-2, 2-dichlorovinyl phosphate; o, o-dimethyl-o-(3-chloro-4-nitrophenyl)-phosphorothioate; pyrethrins with or without a synergist e.g. piperonyl butoxide; D.D.T.; dieldrin and benzene hexachloride. The composition may contain other pesticides e.g. miticides, acarcides, bactericicles or nematocides providing they do not inhibit the setting of the resin.ALSO:A grindable solid insecticidal composition comprises an insecticide in a thermoset resin. Specified insecticides are o,o-dimethyl-s-(1,2-dicarbethoxyethyl) - phosphorodithioate; o,o-diethyl - o - (2 - isopropyl - 4 - methyl - pyrimidyl - 6) - phosphorothioate; 2,3 - p - dioxanedithiol - s,s - bis - (o,o - diethylphosphorodithioate); o,o,o,o - tetraethyl - s,s - methylene-bis - (phosphorodithioate); o,o - diethyl - o - (2,4-dichlorophenyl) - phosphorothioate; o,o-diethyl-o - p - nitrophenylphosphorothioate; o,o - dimethyl - 1,2 - dibromo - 2,2 - dichloroethyl phosphate; o,o - dimethyl - 2,2 - dichlorovinyl phosphate; o,o - dimethyl - o - (3 - chloro - 4 - nitrophenyl) - phosphorothioate; pyrethrins with or without a synergist such as piperonyl butoxide; D.D.T.; Dieldrin and benzene hexachloride. Specified resins (see Group IV (a)) are unsaturated polyester resins, diisocyanate-modified polyether resins, epoxy resins, amino-aldehyde resins, phenolic resins, e.g. resoles and the ethers thereof and the resins obtained by curing the liquid polymer of an alkenyl phenol with formaldehyde or a source of formaldehyde. The compositions may be powdered and preferably mixed with a particulate filler, e.g. diatomaceous earth, or may be in the form of a wettable powder containing a surface-active agent or a deflocculating agent, e.g. sodium salt of di-isobutylnaphthalene sulphonic acid "Orotan" (Registered Trade Mark). The compositions may contain other pesticides, e.g. miticides, acaricides, bactericides or nematocides providing they do not inhibit the setting of the resin. The solid compositions are prepared by mixing the insecticide with the precursor of the thermosetting resin and setting the mixture.