Apple, Pesticide Dip Test #1, 1992

Abstract

Four pesticides, carbaryl (Sevin XLR 3.75 ml per liter [3 pt/100 gal]); methyl parathion (Penncap M 7.5 ml/liter [1 pt/100 gal]); chlorpyrifos (Lorsban 50W 4.78 g/liter [3.99 lb/100 gal]); azinphosmethyl [Guthion 35W 4.78 g/liter] + methomyl (Lannate 7.5 ml/ liter [3.89 lb + 3 pt/100 gal respectively]), and a water control were evaluated (6X concentration) where X = 50 gal/acre in this experiment. RBLR larvae of various sizes and ages were collected in their leaf spin-ups from a commercial orchard where populations were sampled in our 1991 studies. Foliage used in the experiment was collected from unsprayed apple trees at the experiment station in Winchester. Solutions of each treatment pesticide were prepared in 1 gal jars. Twigs bearing more than 40 leaves (for each treatment) were dipped in the appropriate solution for 15 s and air dried in a fume hood. Twenty cages (1 larva per cage) per replicate were prepared as follows: two 9 dram plastic bottles made up the basic cage unit, one filled with water served as the basal unit. Two plastic vial covers with a small (.64 cm) hole centered in each were stapled together and put in place on top of the base vial. Two apple leaves (previously dipped and dried) were placed so as one leaf lay in close proximity to the other with the petioles extending through the container caps into water in the basal container. The point where the petioles passed through the cap was tightly closed with absorbent cotton to prevent larval escape. One field collected larva was gently removed from its spin-up with a camel’s hair brush and placed between the two leaves in each cage. Finally, the second ventilated plastic vial (which had a 3/4-in hole cut in the bottom that was covered with glued-in-place 100 mesh nylon screening) was inverted over the basal vial and snapped into place in the uppermost of the two previously prepared plastic covers. All cages were held in a room under normal light at 80°F (144°C). Larvae were examined after 24, 48, 72, 96, 120, 144 h for mortality. Death was determined if the larva exhibited no movement after being probed gently.