Insecticidal Effects of Vegetable Oil on Silverleaf Whitefly, 1996

Abstract

Abstract All but the top 3-4 fully expanded leaves were removed from 45-50 cm tomato plant with 7-9 leaves and 35 to 40 cm collard with 6-7 leaves. Plants were exposed for 72 h (Test 1) or 24 h (Test 2) to a greenhouse colony of silverleaf whitefly for oviposition. The plants were then incubated 10 d. Second instars predominated in both tests. The 3 vegetable oils labeled “A”, “B”, and “C” (Integrated Biocentrol Systems, Inc., Lawrenceburg, IN), 20 ml each, were measured into plastic vials with 5 ml of the non-ionic surfactant APSA 80 and mixed using a Vortex mixer for about 1 min. Dilutions of 0.5 and 1.0% were made by adding the correct amount of each mixture drop by drop to a 500 ml beaker filled with R.O. purified water while stirring on a magnetic stirring plate. The dilutions were stirred for an additional 2-3 min for a total stirring time of 5-10 minutes. All mixtures emulsified well. APSA 80 [0.04%(AI)] and Sunspray Ultra Fine Oil (Sun Refining & Marketing Co., Philadelphia, PA), were also tested and water was used the check. Leaves bearing an average of 120 whitefly nymphs (range: 70-179) were removed from the plant and placed abaxial side up at the bottom of a Potter Spray Tower. The tower was operated at 10 psi to deliver a volume of 3 ml. Treated leaves were placed, petiole down, in water-filled 20ml vials and incubated in an insectary 25 ± 2°C, 55-60%RH and a photoperiod of 14:10 (L:D) h for 5-7 days. Because of non-uniform age distribution in the first test, only dead 2nd instars and live 3rd and 4th instars were recorded. Pupae (dead or alive) were not recorded because they would have been 3rd or 4th instars when treated. For the second test, all dead and live whitefly nymphs were counted under a stereoscopic microscope.