Seasonal Dilute Insecticide Experiment, 1989

Experimental sprays were applied to run-off to single-tree plots in a randomized block design consisting of 2 replicates of'Golden Delicious' and 2 replicates of'Yorking'. Treated single trees were separated by others not sprayed with insecticides. The trees were planted to a spacing of 20 × 35 ft. Sprays were applied with a John Bean sprayer, 35 gal/min pump, equipped with a spray mast carrying 7 spray guns arranged to wet the uniformly trimmed trees (ca 400 GPA). Approximately 6.0 gal of spray were applied/replicate tree. Dates of application were: 26 Apr (RH compounds only); 23 May; 8 and 21 Jun, 5 and 19 Jul; 2, 15, and 30 Aug. The treatments XRD-473 (with and without Lorsban 50 WP), at 563 ml/100 gals, received 1.69 liters/100 gal (0.1875 lb AI/100 gal) of XRD-473 on the spray dates of 23 May and 8 Jun instead of the rates listed in the tables. Guthion 35 WP was added to the RH-5849 treatment on 23 May, 8 Jun, 19 Jul, 2 and 15 Aug. Effectiveness on the aphid complex was evaluated by counting the number of aphid-infested leaves/10 top terminals, and the number of aphids/most infested leaf. The effect of the sprays on the white apple leafhopper was evaluated by counting the number of nymphs/25 leaves/tree. Effectiveness of the test chemicals on the European red mite and Z. mali was evaluated by counting the mites several times during the season on samples of 25 leaves/tree, 100 leaves/treatment. The effect of sprays on the predator S. punctum was evaluated by 3-min counts of adults and larvae around the periphery of the test trees. Spotted tentiform leafminer was evaluated by a 5-min count of mines around the periphery of the test trees. Effectiveness of chemicals on fruit feeders was assessed by scoring for injury all drops after 1 Jul and 2 picked samples on 15 Aug and 19 Sep. Apple samples averaged 198 fruits/replicate and 792/treatment. Pest pressure was heavy throughout the season. Russet ratings were based on 50 Golden Delicious apples/replicate, 100/treatment. Fruits were rated as follows: 0 = no russeting or enlarged lenticels; 1 = no russeting lent lenticels enlarged, rough and raised to touch; 2 = 1-10% surface russeted; 3 = 11-15% surface russeted; 4 = 26-50% surfce russeted; and 5 = >50% surface russeted.