EFFICACY AND RESIDUES OF FOLIAR SPRAYS AGAINST THE LETTUCE APHID, NASONOVIA RlBlSNIGRI (HOMOPTERA:APHIDIDAE), ON CRISPHEAD LETTUCE

The systemic insecticides disul fo ton. oxydemeton-methyl and demeton, were highl y effective in controlling the lettuce aphid, NasOIIOI'ia rihisnigri (Mos ley) (Homop-tera: Aphididae), when sprayed on cri spheadlettuce at the earl y stage of heading. Total res idues of di sul fo ton, applied at 1.12 kg AI/ha and oxydemelOn-methyl at 0.56 kg A ll ha. diminished to less th an 0.06 ppm 28 days after appli cation, making these compounds strong candidates to replace the di scontinued demeton. The local systemic compounds pi rimicarb and methamidophos we re intelmediate in effec ti veness betwee n the sys-temics li sted and contac t insecticides such as endosulfan, mevinphos and parathion when applied to lettuce before the heading stage. Seven methods of applying meth-amidophos at 1. 1 kg AI/ha all prov ided equall y significant leve ls of lettuce aphid control