OVER-TREE IRRIGATION IN PEAR ORCHARDS INFLUENCES PERSISTENCE OF FOLIAR RESIDUES OF 4 PESTICIDES

Residues of two fungicides (dodine and fenarimol) and two insecticide/ acaricides (amitraz and formetanate) on pear (Pyrus communis L.) leave s were reduced by over-tree sprinkler irrigation applied 24 or 72 hour s after pesticide treatment. The difference in residue persistence fol lowing over-tree irrigation applied at 24 vs. 72 hours after pesticide treatment was significant only for fenarimol. Residues on leaves from nonirrigated trees at 96 hours post-treatment had declined 24% to 57% from initial levels. Over-tree irrigation further reduced residues by 14% to 47%. For all compounds except dodine, foliar residues measured at 96 hours post-treatment were reduced from initial levels to a grea ter extent by factors other than over-tree irrigation.