STARCH UREA-FORMALDEHYDE MATRIX ENCAPSULATION OF SOLID AGROCHEMICALS .3. STUDIES AND BIOEFFICACY TRIALS ON DOUBLE ENCAPSULATION

A technique for the double encapsulation of carbofuran in starch urea formaldehyde (Starch-UF) matrix has been developed. The solid particle s of carbofuran were first microencapsulated with UF resin and these m icrocapsules were then dispersed in the Starch-UF matrix to obtain a g ranular formulation. The rate of release of carbofuran from these gran ules was found to be governed by its diffusion through the solid UF re sin shell and was significantly slower than from the single encapsulat ed granular formulation prepared by dispersing uncoated carbofuran in Starch-UF matrix. The bioefficacy of these double encapsulated granule s (Encecap-D 3G), was evaluated for persistence against rice pests in paddy and against subterranean pests in potato, in comparison with con ventional formulations of carbofuran, phorate, quinalphos, aldicarb an d cadusafos. The persistence of Encecap-D 3G was found to be better th an that of the standard formulation in the cultivation of paddy under flooded conditions and in the cultivation of potato. The order of effi cacy was found to be: White grubs-Encecap-D 3G > quinalphos > cadusafo s > aldicarb > phorate > Furadan 3G; Nematodes-cadusafos > Encecap-D 3 G > quinalphos > aldicarb > phorate > 'Furadan' 3G.