MORTALITY OF TETRANYCHUS URTICAE KOCH (ACARI: TETRANYCHIDAE) FROM ABAMECTIN RESIDUES: EFFECTS OF HOST PLANT, LIGHT, AND SURFACTANTS

Residues of abamectin (avermectin, Avid), 15 ppm; abamectin + Leaf Act 80, 15 + 25 ppm; abamectin + Sunspray oil, 15 + 25 ppm, and a water control were evaluated for length of control of twospotted spider mite, Tetranychus urticae Koch, on 3 host species: azalea, Rhododendron × ‘Red Ruffle’; lima bean, Phaseolus limensis var. limenus L. H. Bailey cv. ‘Henderson’ bush; and peach, Prunus persica L. Batsch cv. ‘Nemaguard’; and under sunlight and fluorescent light regimes.

Abamectin alone or in combination with the surfactants, 21 days post treatment, resulted in 42.6 – 91.8% and 88 – 93% mite mortality under sunlight and fluorescent light, respectively. No treatments on azalea or peach under sunlight caused > 37% mortality. Treatments caused similar mite mortality 1 day posttreatment under fluorescent light, but after day 1 treatments on peach caused < 62 % mortality while treatments on azalea caused < 46% mortality. The addition of oil increased mite mortality significantly on beans under sunlight at 14 days. At 21 days both Leaf Act 80 and oil increased mite mortality on bean compared to abamectin alone.