1-Alkyl-5-substituted-4-chloropyrazole-3-yl-(thio)phosphates and (thio)phosphonates of the formula ##STR1## wherein R is lower alkyl; R.sup.1 is lower alkoxy; R.sup.2 is lower alkyl or lower alkoxy; X is chloro or the group --SR.sup.3 wherein R.sup.3 is lower alkyl; and Y is sulfur or oxygen are insecticidal, and are particularly effective against cabbage looper.
Compounds of the formula: ##STR1## wherein R is lower alkyl; R.sup.1 is lower alkoxy or lower alkylthio; R.sup.2 is lower alkyl or lower alkoxy; R.sup.3 is lower alkyl; and Y is sulfur or oxygen, possess fungicidal and insecticidal activity.